Soil Science
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Questions and Answers

What is primarily examined in the first order of soil survey?

  • Agricultural productivity
  • General land use planning
  • Broad reconnaissance of soil types
  • Delineation for experiments and building sites (correct)

    • What is NOT a layer in the hierarchy of soil classification as described?

  • Order
  • Family
  • Great group
  • Type (correct)

    • Which of the following is considered in land suitability classes?

  • Soil nutrient quality
  • Plant growth requirements
  • Limitations to tillage and plant rooting (correct)
  • Microclimate effects

    • Which of these properties is NOT part of soil taxonomy based on USDA soil surveys?

    <p>Organic carbon content</p> Signup and view all the answers

    What is the primary purpose of organizing knowledge about soils?

    <p>Understand relationships among different soils</p> Signup and view all the answers

    Which factor is NOT directly associated with soil formation processes?

    <p>Nutrient absorption by plants</p> Signup and view all the answers

    What is the primary component of soil solids?

    <p>Minerals</p> Signup and view all the answers

    During which stage of soil formation does chemical weathering occur?

    <p>Soil horizon formation</p> Signup and view all the answers

    Which method is NOT an approach in soil study?

    <p>Acid-base chemistry</p> Signup and view all the answers

    What is a pedon in soil science?

    <p>The basic unit of soil measuring 1-10m2</p> Signup and view all the answers

    Which soil texture is characterized by the highest bulk density?

    <p>Sand</p> Signup and view all the answers

    Which process is primarily driven by rainfall in soil formation?

    <p>Chemical weathering</p> Signup and view all the answers

    What is the primary reason tropical soils weather faster than other soils?

    <p>Warmer temperatures</p> Signup and view all the answers

    What component contributes most to the soil organic matter (SOM) accumulation in grasslands compared to forests?

    <p>Faster turnover of vegetative matter</p> Signup and view all the answers

    Which of the following is not a primary reason for the decline of organic matter (OM) due to cultivation?

    <p>Higher moisture retention</p> Signup and view all the answers

    Which fungus is associated with cellulose decomposition in composting?

    <p>Aspergillus</p> Signup and view all the answers

    What is the typical carbon-to-nitrogen (C/N) ratio of finished compost?

    <p>14:1 to 20:1</p> Signup and view all the answers

    In soil chemistry, which ions have a molar mass representation of 1 cmol equal to 0.40 g for calcium?

    <p>Calcium</p> Signup and view all the answers

    What process helps in the microbial transformation of sulfate into sulfide?

    <p>Desulfovibrii activity</p> Signup and view all the answers

    What role do mycorrhizae predominantly play in soil fertility?

    <p>Enhancing phosphorus absorption</p> Signup and view all the answers

    Which component of soil organic matter is usually present in the highest percentage?

    <p>Cellulose</p> Signup and view all the answers

    Which of the following microbial groups is classified as ectotrophic mycorrhiza?

    <p>External mantle fungi</p> Signup and view all the answers

    What is one result of flooding in soil management?

    <p>Reduction of ferric phosphate</p> Signup and view all the answers

    What is the primary contribution of rainfall to soil formation?

    <p>Hydrolysis and leaching</p> Signup and view all the answers

    Which factor significantly impacts the reaction rates during soil formation in tropical climates?

    <p>Temperature</p> Signup and view all the answers

    Which of the following is NOT a stage of soil formation?

    <p>Pollination</p> Signup and view all the answers

    What is the role of living organisms in the soil formation process?

    <p>Causing bioturbation</p> Signup and view all the answers

    Which of the following statements about soil classification is accurate?

    <p>Soil texture is a primary factor in classification.</p> Signup and view all the answers

    How does organic matter (OM) generally affect soil characteristics?

    <p>Enhances nutrient retention</p> Signup and view all the answers

    Which soil horizon represents the transition between soil layers?

    <p>AB horizon</p> Signup and view all the answers

    Which of the following is a characteristic of heavy minerals found in soil?

    <p>High magnetic susceptibility</p> Signup and view all the answers

    What is a primary purpose of soil classification?

    <p>To predict soil behavior and estimate productivity</p> Signup and view all the answers

    In the hierarchy of soil classification, which level directly addresses moisture and temperature regimes?

    <p>Suborder</p> Signup and view all the answers

    Which level of soil survey would be most appropriate for regional planning?

    <p>5th</p> Signup and view all the answers

    Which of the following is NOT a consideration for land suitability classes?

    <p>Soil mineral composition</p> Signup and view all the answers

    What is the basic unit in soil classification as outlined in the content?

    <p>Series</p> Signup and view all the answers

    Which of the following is a key property observed in soil taxonomy?

    <p>Soil genesis</p> Signup and view all the answers

    Which order of soil survey is used primarily for detailed urban planning?

    <p>2nd order</p> Signup and view all the answers

    What factor primarily influences the productivity of a specific soil type?

    <p>Soil organic matter content</p> Signup and view all the answers

    What is the range of land area covered by the 3rd order of soil survey?

    <p>1.6-16 ha</p> Signup and view all the answers

    What process primarily organizes knowledge about soils and their relationships?

    <p>Soil classification</p> Signup and view all the answers

    Which soil order is characterized by high organic matter and is suitable for pasture when conserved?

    <p>Histosol</p> Signup and view all the answers

    What process describes the conversion of inorganic nitrogen into organic nitrogen in soil?

    <p>Immobilization</p> Signup and view all the answers

    Which of the following describes the soil temperature regime with a mean annual temperature of greater than 22°C?

    <p>Hyperthermic</p> Signup and view all the answers

    What is the main characteristic of Agrilic soil horizons?

    <p>Illuvial horizon of clay accumulation</p> Signup and view all the answers

    Which type of bacteria is primarily responsible for denitrification in soil, converting nitrates back to nitrogen gas?

    <p>Pseudomonas</p> Signup and view all the answers

    What factor most significantly affects the accumulation of soil organic matter (SOM)?

    <p>Temperature</p> Signup and view all the answers

    Which type of mycorrhizae primarily penetrates plant root cells?

    <p>Endomycorrhiza</p> Signup and view all the answers

    What is the primary role of actinomycetes in soil?

    <p>Attacking and simplifying organic compounds</p> Signup and view all the answers

    Why does organic matter (OM) accumulate more in grasslands compared to forests?

    <p>Faster turnover of vegetative matter</p> Signup and view all the answers

    In the context of composting, what is the typical C/N ratio?

    <p>14/1 to 20/1</p> Signup and view all the answers

    What microbial process is responsible for reducing sulfate to sulfide?

    <p>Sulfur reduction</p> Signup and view all the answers

    What contributes to the enhancement of soil organic matter decline during cultivation?

    <p>Enhanced oxidation and microbial activity</p> Signup and view all the answers

    Which of the following processes occurs during thermophilic stages of composting?

    <p>Pathogen destruction</p> Signup and view all the answers

    Which of the following is a component of soil organic matter (SOM) typically found in the greatest percentage?

    <p>Cellulose</p> Signup and view all the answers

    What is a significant byproduct of microbial sulfur transformation in soils?

    <p>Organic acids</p> Signup and view all the answers

    Which method can help mitigate iron toxicity in sodic soils?

    <p>Irrigation and regular drainage</p> Signup and view all the answers

    What is the primary benefit of liming with CaCO3 in acidic soils?

    <p>Neutralize soil acidity</p> Signup and view all the answers

    Which of the following statements about soil pore space is correct?

    <p>Micropores retain water for plants</p> Signup and view all the answers

    What role do composts play in managing saline soils?

    <p>Enhance soil fertility</p> Signup and view all the answers

    Which factor is NOT likely to increase bulk density in soils?

    <p>High organic matter content</p> Signup and view all the answers

    Which practice is beneficial for improving soil texture in lowland or paddy soils?

    <p>Application of organic matter</p> Signup and view all the answers

    What is a common characteristic of sodic soils?

    <p>High pH values</p> Signup and view all the answers

    Which practice may alleviate zinc deficiency in soils effectively?

    <p>Spraying with foliar fertilizers containing zinc</p> Signup and view all the answers

    What is the effect of waterlogging on soil conditions?

    <p>Leads to anaerobic conditions</p> Signup and view all the answers

    Which property primarily influences the retention of nutrients and moisture in soils?

    <p>Soil texture</p> Signup and view all the answers

    Which factor primarily influences particle rearrangement in soil formation?

    <p>Water movement</p> Signup and view all the answers

    What is the main function of the nutrient leaching process in soil?

    <p>To remove excess nutrients and salts</p> Signup and view all the answers

    Which soil horizon forms right above the bedrock?

    <p>Transition horizon</p> Signup and view all the answers

    In soil chemistry, what does carbonation primarily contribute to?

    <p>Formation of carbonates like calcium carbonate</p> Signup and view all the answers

    Which approach in soil study analyzes the physical properties of soil?

    <p>Physics</p> Signup and view all the answers

    What primarily defines the bulk density of soil?

    <p>Soil texture and structure</p> Signup and view all the answers

    Which of the following is NOT a factor affecting soil formation?

    <p>Human intervention</p> Signup and view all the answers

    What effect does organic matter generally have on soil characteristics?

    <p>Enhances soil fertility and water retention</p> Signup and view all the answers

    What is the main purpose of soil taxonomy in soil study?

    <p>To understand relationships among different soil types</p> Signup and view all the answers

    Which of the following best describes the characteristics of the first order of soil survey?

    <p>It delineates land areas smaller than one hectare.</p> Signup and view all the answers

    Which level of soil classification directly addresses the arrangement of soil properties?

    <p>Great group</p> Signup and view all the answers

    What factor is NOT typically considered in land suitability classes?

    <p>Soil nutrient content</p> Signup and view all the answers

    Which type of soil survey is suited for agricultural and urban planning?

    <p>Second order</p> Signup and view all the answers

    Which factor is associated with soil genesis and not a property of the soil itself?

    <p>Climate conditions</p> Signup and view all the answers

    In soil classification, what is the basic unit referred to in the hierarchy?

    <p>Series</p> Signup and view all the answers

    What characteristic is typically used to differentiate soil orders?

    <p>Diagnostic horizons</p> Signup and view all the answers

    Which of the following soil properties is readily observable?

    <p>Soil texture</p> Signup and view all the answers

    Which order of soil survey primarily focuses on exploratory activities?

    <p>Fifth order</p> Signup and view all the answers

    What is the process by which inorganic nitrogen is converted into organic nitrogen in soil?

    <p>Symbiotic N-fixation</p> Signup and view all the answers

    Which of the following soil temperature regimes has a mean annual temperature (MAT) of 15°C - 22°C?

    <p>Thermic</p> Signup and view all the answers

    Which soil order is typically associated with high organic matter, making it suitable for pasture when conserved?

    <p>Histosol</p> Signup and view all the answers

    Which factor does NOT significantly affect the accumulation of soil organic matter (SOM)?

    <p>Soil color</p> Signup and view all the answers

    What is the characteristic feature of an Argilic soil horizon?

    <p>Illuvial horizon with clay accumulation</p> Signup and view all the answers

    In the process of composting, what is generally destroyed during the thermophilic stage?

    <p>Pathogens</p> Signup and view all the answers

    Which process in soil chemistry primarily converts organic matter into ammonium?

    <p>Ammonification</p> Signup and view all the answers

    What is the primary role of fungi in the decomposition of organic matter?

    <p>Decomposition of lignin and cellulose</p> Signup and view all the answers

    Which group of microorganisms is primarily responsible for reducing sulfate to sulfide?

    <p>Desulfovibrio and Desulfotomaculum</p> Signup and view all the answers

    Which of the following percentages represents the typical composition of cellulose in soil organic matter?

    <p>15-60%</p> Signup and view all the answers

    Which soil component most likely leads to enhanced oxidation and microbial activity when cultivation occurs?

    <p>Soil organic matter</p> Signup and view all the answers

    What type of mycorrhizae primarily helps in the penetration of plant root cells?

    <p>Endomycorrhiza</p> Signup and view all the answers

    Which organic component in soil is likely to have the highest percentage overall?

    <p>Cellulose</p> Signup and view all the answers

    What is the typical carbon-to-nitrogen (C/N) ratio range for finished compost?

    <p>14/1 – 20/1</p> Signup and view all the answers

    Which process is NOT associated with microbial metabolism of sulfur compounds?

    <p>Transformation of nitrogen</p> Signup and view all the answers

    What amendment is recommended to counteract high salinity in soils?

    <p>Irrigation and regular drainage</p> Signup and view all the answers

    Which organic fertilizer application method helps improve phosphorus availability in soils?

    <p>Apply mycorrhiza-containing organic fertilizers</p> Signup and view all the answers

    What is a common soil texture that holds water in micropores?

    <p>Clay</p> Signup and view all the answers

    Which factor significantly influences bulk density in soils?

    <p>Organic matter content</p> Signup and view all the answers

    Which soil condition indicates a danger of iron toxicity?

    <p>Soil EC greater than 4 mmhos/cm</p> Signup and view all the answers

    In which type of soil would you most likely need to implement methods to combat high iron concentration?

    <p>Acid sulfate soils</p> Signup and view all the answers

    Which method is effective for managing waterlogged soils?

    <p>Employ raised-bed technology</p> Signup and view all the answers

    What nutrient deficiency is commonly addressed with foliar fertilizer applications?

    <p>Zinc</p> Signup and view all the answers

    Which of these practices aids in the reduction of sodium levels in sodic soils?

    <p>Irrigation and drainage</p> Signup and view all the answers

    What is the main role of calcium carbonate in soil management?

    <p>Reduce acidity</p> Signup and view all the answers

    Which process involves the addition of organic matter during soil formation?

    <p>OM addition</p> Signup and view all the answers

    What primarily affects the bulk density of soil?

    <p>Soil texture and composition</p> Signup and view all the answers

    In soil chemistry, how does the presence of H2CO3 affect mineral formation?

    <p>It aids in carbonate dissolution.</p> Signup and view all the answers

    Which horizon represents the transition zone within a soil profile?

    <p>AB horizon</p> Signup and view all the answers

    Which factor is known to accelerate the weathering process in soils?

    <p>Higher rainfall amounts</p> Signup and view all the answers

    Which component constitutes the largest fraction of soil solids?

    <p>Minerals</p> Signup and view all the answers

    What effect does living organisms have on soil structure?

    <p>Promote bioturbation</p> Signup and view all the answers

    Which of the following terms refers to the basic unit of soil classification?

    <p>Pedon</p> Signup and view all the answers

    Which of the following soil orders is characterized by the accumulation of organic matter and is suitable for pasture when conserved?

    <p>Histosol</p> Signup and view all the answers

    What process describes the conversion of organic nitrogen into inorganic nitrogen forms in soil via microbial activity?

    <p>Ammonification</p> Signup and view all the answers

    Which of the following temperature regimes indicates a mean annual temperature between 15°C to 22°C?

    <p>Thermic</p> Signup and view all the answers

    In soil chemistry, which microbial process is responsible for the transformation of ammonium to nitrite and then to nitrate?

    <p>Nitrification</p> Signup and view all the answers

    What is the primary characteristic of Oxic soil horizons?

    <p>Very weathered layers of iron and aluminum</p> Signup and view all the answers

    What is the characteristic size range of the land covered by the 2nd order of soil survey?

    <p>0.6 to 4 hectares</p> Signup and view all the answers

    Which level of soil classification divides the order by moisture and temperature regime?

    <p>Suborder</p> Signup and view all the answers

    Which microorganism is primarily responsible for reducing sulfate to sulfide in the soil?

    <p>Desulfovibrii</p> Signup and view all the answers

    What is the main purpose of soil taxonomy as described?

    <p>To organize knowledge about soils</p> Signup and view all the answers

    What is the typical carbon-to-nitrogen (C/N) ratio of compost before it is fully decomposed?

    <p>14/1 – 20/1</p> Signup and view all the answers

    Which soil survey order is intended primarily for very intensive studies, like building site evaluation?

    <p>1st order</p> Signup and view all the answers

    In terms of soil organic matter accumulation, which factor significantly contributes more to grasslands compared to forests?

    <p>Faster turnover of vegetative matter</p> Signup and view all the answers

    In terms of land suitability classes, which of the following is a notable consideration?

    <p>Limitations to tillage and plant rooting</p> Signup and view all the answers

    Which of the following best describes ectotrophic mycorrhizae?

    <p>They form an exterior mantle around roots.</p> Signup and view all the answers

    What is the effect of flooding on ferric phosphate in soil?

    <p>It reduces ferric phosphate availability.</p> Signup and view all the answers

    What does the hierarchy of soil classification conclude with at the most granular level?

    <p>Series</p> Signup and view all the answers

    Which of the following factors is NOT listed as a concern for determining land suitability?

    <p>Soil organic matter content</p> Signup and view all the answers

    Which chemical property of soil is indicated by the given equivalence of 1 cmol to 0.40 g for calcium?

    <p>Exchange capacity</p> Signup and view all the answers

    What does the term 'great group' refer to in soil classification?

    <p>Division by arrangement and properties</p> Signup and view all the answers

    Which soil process is primarily associated with the microbial decomposition of organic materials like cellulose and hemicellulose?

    <p>Composting</p> Signup and view all the answers

    Which factor most substantially affects the moisture content and thus the organic matter accumulation in soils?

    <p>Precipitation patterns</p> Signup and view all the answers

    What is the main distinguishing characteristic of the 4th order soil survey?

    <p>It covers broad land use with less detail</p> Signup and view all the answers

    Which factor is primarily concerned with the genesis of soil and influences its formation?

    <p>Soil property</p> Signup and view all the answers

    What is one characteristic differentiation of actinomycetes in the soil?

    <p>They produce antibiotics.</p> Signup and view all the answers

    Which component of soil organic matter typically contains the least percentage?

    <p>Lignin</p> Signup and view all the answers

    What is the recommended amendment to reduce iron toxicity in sodic soils?

    <p>Apply gypsum (CaSO4)</p> Signup and view all the answers

    Which soil texture holds water in micropores and supports root growth?

    <p>Clay</p> Signup and view all the answers

    What is the primary function of using organic matter in managing high salinity soils?

    <p>Increase nutrient availability</p> Signup and view all the answers

    Which statement about dryland soil management is correct?

    <p>Employing raised-bed technology increases water retention</p> Signup and view all the answers

    What is one of the factors affecting bulk density in soils?

    <p>Soil texture</p> Signup and view all the answers

    How can lowland or paddy soils be managed to address zinc deficiency?

    <p>Apply phosphatic fertilizers</p> Signup and view all the answers

    Which approach is recommended to reduce acidity in soils?

    <p>Liming using CaCO3, CaO, or Ca(OH)2</p> Signup and view all the answers

    Which of the following is a characteristic of soils affected by iron toxicity?

    <p>Brown, yellowish brown, red brown</p> Signup and view all the answers

    Which method can help alleviate conditions of waterlogged soils?

    <p>Construct canals for drainage</p> Signup and view all the answers

    What is a common result of organic matter decomposition in waterlogged soils?

    <p>Increased CO2 levels</p> Signup and view all the answers

    Which process involves the reaction of H2CO3 that leads to the formation of calcium carbonate?

    <p>Carbonation</p> Signup and view all the answers

    What is the primary soil component responsible for the majority of soil's inorganic structure?

    <p>Minerals</p> Signup and view all the answers

    Which of the following factors is NOT part of the five factors affecting soil formation?

    <p>Production of organic compounds</p> Signup and view all the answers

    In which stage of soil formation does organic matter (OM) addition occur?

    <p>Particle rearrangement</p> Signup and view all the answers

    What does the pedon represent in soil classification?

    <p>A basic unit of soil</p> Signup and view all the answers

    Which method is commonly used to determine soil texture?

    <p>Hydrometer/pipette</p> Signup and view all the answers

    Which component of soil gas primarily influences the soil's aeration?

    <p>O2</p> Signup and view all the answers

    What role does bioturbation play in soil formation?

    <p>It leads to particle rearrangement.</p> Signup and view all the answers

    Which soil order is characterized by arable suitability and has no conservation potential?

    <p>Entisol</p> Signup and view all the answers

    What process involves the conversion of organic nitrogen back into inorganic nitrogen compounds in the soil?

    <p>Denitrification</p> Signup and view all the answers

    Which type of soil horizon is characterized by a thick illuvial accumulation of clay, aluminum, iron, and organic matter?

    <p>Argilic</p> Signup and view all the answers

    Which temperature regime indicates a mean annual temperature below 8°C and is typically found in colder regions?

    <p>Pergelic</p> Signup and view all the answers

    Which of the following processes mainly results in the transformation of organic matter into ammonia in soil?

    <p>Ammonification</p> Signup and view all the answers

    What is the main purpose of conducting a soil survey?

    <p>To inventory soil resources and estimate productivity</p> Signup and view all the answers

    Which order of soil survey is primarily focused on detailed studies for experiments?

    <p>1st Order</p> Signup and view all the answers

    What is a primary characteristic used to differentiate soil orders in classification?

    <p>Major diagnostic horizon</p> Signup and view all the answers

    What does the 'great group' level of soil classification primarily organize according to?

    <p>Arrangement of horizons</p> Signup and view all the answers

    In soil taxonomy, which of the following is NOT a principal factor affecting soil genesis?

    <p>Land use practices</p> Signup and view all the answers

    Which consideration is NOT included in land suitability classes?

    <p>Soil texture</p> Signup and view all the answers

    What is the range of land area covered by the 4th order of soil survey?

    <p>16-252 hectares</p> Signup and view all the answers

    Which level of soil classification deals with the division according to uses in plant growth?

    <p>Family</p> Signup and view all the answers

    In soil classification, what is the significance of the 'suborder' level?

    <p>It divides order according to moisture and temperature regimes.</p> Signup and view all the answers

    What is the basic unit of soil classification in the mentioned taxonomy?

    <p>Series</p> Signup and view all the answers

    Which method is effective in managing salinity in soils with high soluble salts?

    <p>Irrigation and regular drainage</p> Signup and view all the answers

    What is a common practice for alleviating iron toxicity in paddy soils?

    <p>Regular drainage</p> Signup and view all the answers

    Which practice is recommended for improving soil texture and enhancing moisture retention?

    <p>Apply compost</p> Signup and view all the answers

    What is the primary function of micropores in soil?

    <p>Retention of water</p> Signup and view all the answers

    Which statement best describes the effect of soil texture on bulk density?

    <p>Clay retains moisture better than sand</p> Signup and view all the answers

    Which nutrient management technique addresses zinc deficiency in crops?

    <p>Apply foliar fertilizers containing zinc</p> Signup and view all the answers

    What is the relationship between organic matter decomposition and soil properties?

    <p>Decomposition moderates pH and enhances nutrient availability</p> Signup and view all the answers

    Which of the following is a characteristic of sodic soils?

    <p>Excessive sodium content</p> Signup and view all the answers

    What is a key factor influencing soil genesis in tropical climates?

    <p>Rainfall patterns</p> Signup and view all the answers

    Which approach can help in managing waterlogged conditions in lowland soils?

    <p>Constructing drainage canals</p> Signup and view all the answers

    What is the main factor affecting the accumulation of soil organic matter (SOM)?

    <p>Microbial activity</p> Signup and view all the answers

    Which component of soil organic matter generally has the lowest percentage?

    <p>Lignin</p> Signup and view all the answers

    How does flooding most directly influence soil composition?

    <p>By reducing ferric phosphate</p> Signup and view all the answers

    What is the average carbon-to-nitrogen (C/N) ratio for finished compost?

    <p>14:1 - 20:1</p> Signup and view all the answers

    Which group of microbes is primarily involved in the reduction of sulfate to sulfide?

    <p>Desulfovibrii &amp; Desulfotomaculum</p> Signup and view all the answers

    What happens to organic matter when soil is cultivated?

    <p>It declines due to enhanced oxidation.</p> Signup and view all the answers

    What specific role do mycorrhizae play in soil health?

    <p>Assist in phosphorus absorption</p> Signup and view all the answers

    Which type of mycorrhizae are known to penetrate plant root cells?

    <p>Both B and C</p> Signup and view all the answers

    What property is primarily examined when assessing soil texture?

    <p>Particle size distribution</p> Signup and view all the answers

    Which factor significantly affects the decomposition of cellulose in composting?

    <p>Microbial community composition</p> Signup and view all the answers

    What is the primary chemical process involved in the transformation of calcite into calcium carbonate under acidic conditions?

    <p>Carbonation</p> Signup and view all the answers

    Which factor primarily influences the rate of chemical weathering in soils?

    <p>Temperature and moisture</p> Signup and view all the answers

    Which stage of soil formation primarily involves the addition of organic matter to the soil profile?

    <p>Organic matter addition</p> Signup and view all the answers

    In the context of soil components, which statement accurately describes the gas content of soil?

    <p>Soil gas composition is primarily made up of carbon dioxide.</p> Signup and view all the answers

    Which term refers to the natural body that serves as a medium for plant growth?

    <p>Pedon</p> Signup and view all the answers

    Which physical property of soil is characterized by the ability to resist deformation and compaction?

    <p>Plasticity</p> Signup and view all the answers

    What role do living organisms play in the soil formation process?

    <p>They cause bioturbation, mixing soil layers.</p> Signup and view all the answers

    Which of the following approaches in soil study focuses on the classification and description of soil types?

    <p>Survey &amp; classification</p> Signup and view all the answers

    Which soil order is primarily designed for extensive land use and encompasses areas of 16 to 252 hectares?

    <p>4th order</p> Signup and view all the answers

    In soil classification, what is the term for the division that categorizes soil based on its major diagnostic horizon?

    <p>Order</p> Signup and view all the answers

    Which of the following factors is considered in land suitability classes that affects soil management?

    <p>Moisture retention</p> Signup and view all the answers

    What does the 'series' level in soil taxonomy primarily denote?

    <p>Basic unit of classification</p> Signup and view all the answers

    Which type of property is NOT readily observable and is also crucial for understanding soil genesis?

    <p>Soil chemical reactions</p> Signup and view all the answers

    What aspect of soil fertility primarily influences plant growth according to its classification?

    <p>Organic matter levels</p> Signup and view all the answers

    In the context of soil survey levels, which level involves a very intensive survey for detailed experimental purposes?

    <p>1st order</p> Signup and view all the answers

    Which category in land suitability classes primarily addresses the potential for erosion and runoff?

    <p>Erosion/runoff potential</p> Signup and view all the answers

    Which level of classification divides soil into suborders based on moisture and temperature regimes?

    <p>Suborder</p> Signup and view all the answers

    How does the term 'family' in soil taxonomy primarily categorize soil?

    <p>According to plant growth uses</p> Signup and view all the answers

    Which soil order is characterized by an accumulation of organic matter and a suitability for pasture when conserved?

    <p>Histosol</p> Signup and view all the answers

    Which process relates to the conversion of nitrogen gas into ammonia in soil through non-symbiotic means?

    <p>Ammonification</p> Signup and view all the answers

    Which type of bacteria primarily facilitates the solubilization of calcium phosphate in the soil?

    <p>Pseudomonas</p> Signup and view all the answers

    What significantly affects the accumulation of soil organic matter in different ecosystems?

    <p>Turnover rate of vegetative matter</p> Signup and view all the answers

    Which soil temperature regime is characterized by a mean annual temperature between 15°C and 22°C?

    <p>Thermic</p> Signup and view all the answers

    Which statement regarding the terms 'aerobic' and 'anaerobic' is accurate in the context of soil microorganisms?

    <p>Aerobic bacteria require oxygen for their metabolic processes.</p> Signup and view all the answers

    Which component of soil organic matter has the highest range in percentage?

    <p>Cellulose</p> Signup and view all the answers

    Which type of mycorrhizae is known for penetrating plant root cells?

    <p>Endomycorrhizae</p> Signup and view all the answers

    How does microbial activity affect organic matter in cultivated soils?

    <p>Enhances the oxidation process</p> Signup and view all the answers

    Which of the following fungal genera is most associated with cellulose decomposition?

    <p>Aspergillus</p> Signup and view all the answers

    What is the primary product of the thermophilic stage in composting?

    <p>Humus-like organic material</p> Signup and view all the answers

    Which process is primarily driven by the activity of Iron bacteria in soils?

    <p>Ferrous oxidation</p> Signup and view all the answers

    What is the carbon-to-nitrogen (C/N) ratio range of finished compost?

    <p>14:1 - 20:1</p> Signup and view all the answers

    Which of the following chemical forms of sulfur is involved in microbial transformation processes?

    <p>All of the above</p> Signup and view all the answers

    What role do Actinomycetes play in soil health?

    <p>Simplify organic compounds</p> Signup and view all the answers

    What practice can help mitigate iron toxicity in flooded soils?

    <p>Regularly drain the soil to manage water levels</p> Signup and view all the answers

    Which soil texture is described as smooth and powdery?

    <p>Silt</p> Signup and view all the answers

    What is a common consequence of excessive soluble sodium in soils?

    <p>Toxic accumulation of soluble salts</p> Signup and view all the answers

    Which approach is NOT advised for managing calcareous soil conditions?

    <p>Regular mulching with nitrogen-rich materials</p> Signup and view all the answers

    Which property is most affected by the bulk density of soil?

    <p>Water infiltration rate</p> Signup and view all the answers

    What aspect is essential for the amendment of sodic soils?

    <p>Utilize gypsum to reclaim sodium.</p> Signup and view all the answers

    Which method is effective in managing waterlogged soils?

    <p>Constructing canals for drainage</p> Signup and view all the answers

    Which component of soil typically provides the most available micronutrients?

    <p>Organic matter</p> Signup and view all the answers

    What characteristic of acid sulfate soil impacts its management?

    <p>Low pH affecting nutrient solubility</p> Signup and view all the answers

    Which of the following is critical for increasing phosphorus availability in soils?

    <p>Use of mycorrhizal fungi</p> Signup and view all the answers

    What is the role of temperature in the chemical reactions associated with soil formation?

    <p>Higher temperatures increase reaction rates according to the rate equation.</p> Signup and view all the answers

    Which of the following factors is least associated with bioturbation in soil formation?

    <p>Heavy rainfall causing erosion.</p> Signup and view all the answers

    Which process involves the dissolution of silica in soil chemistry?

    <p>Solution</p> Signup and view all the answers

    What is the typical bulk density range for clay soils?

    <p>1.13 g/cm3</p> Signup and view all the answers

    In the context of soil classification, what is the meaning of 'polypedon'?

    <p>Multiple hexagonal pedons.</p> Signup and view all the answers

    Which mechanism primarily facilitates the movement of water in the process of soil formation?

    <p>Relief/topography</p> Signup and view all the answers

    Which approach in soil study primarily focuses on understanding the elemental composition and reactions of soil?

    <p>Chemistry</p> Signup and view all the answers

    Which stage of soil formation is directly influenced by the addition of organic matter?

    <p>Soil horizon formation</p> Signup and view all the answers

    Which soil order is characterized by a significant accumulation of organic matter and a high likelihood of being waterlogged?

    <p>Histosol</p> Signup and view all the answers

    What is the primary role of aerobic bacteria in soil nitrogen cycles?

    <p>To convert organic nitrogen into ammonium</p> Signup and view all the answers

    Which process is responsible for the conversion of soil organic matter into ammonia?

    <p>Ammonification</p> Signup and view all the answers

    Which layer of soil is typically described as having a high percentage of illuvial accumulations of aluminum and iron?

    <p>Argilic Horizon</p> Signup and view all the answers

    What aspect of soil determines its suitability for agricultural use, particularly in terms of moisture retention and nutrient availability?

    <p>Soil texture</p> Signup and view all the answers

    Which factor primarily contributes to the accumulation of soil organic matter in grasslands compared to forested areas?

    <p>Faster turnover of vegetative matter</p> Signup and view all the answers

    Which microbial process plays a key role in the reduction of sulfate to sulfide in soil chemistry?

    <p>Desulfovibrio activity</p> Signup and view all the answers

    What is the typical C/N ratio range for finished compost products?

    <p>14:1 to 20:1</p> Signup and view all the answers

    Which property of soil organic matter is influenced by moisture levels?

    <p>Accumulation rate</p> Signup and view all the answers

    Which type of mycorrhizae is characterized by its ability to penetrate plant root cells?

    <p>Endomycorrhiza</p> Signup and view all the answers

    Which chemical property of soils is indicated by the cmol value of calcium?

    <p>Calcium ion concentration</p> Signup and view all the answers

    What effect does flooding generally have on ferric phosphate levels in soil?

    <p>Reduces ferric phosphate levels</p> Signup and view all the answers

    What role do actinomycetes primarily play in soil ecology?

    <p>Breaking down complex organic compounds</p> Signup and view all the answers

    Which of the following fungi is specifically noted for its role in cellulose decomposition?

    <p>Trichoderma</p> Signup and view all the answers

    What is the primary purpose of composting in soil management?

    <p>Create humus-like organic materials</p> Signup and view all the answers

    Which order of soil survey is primarily designed for experimental purposes?

    <p>1st order</p> Signup and view all the answers

    What is the primary criterion for differentiating soil suborders?

    <p>Moisture and temperature regimes</p> Signup and view all the answers

    In soil taxonomy, which level directly correlates with the arrangement of soil particles?

    <p>Great group</p> Signup and view all the answers

    Which of the following best describes land suitability considerations related to erosion?

    <p>Potential for surface runoff</p> Signup and view all the answers

    What type of soil survey would best support extensive community planning?

    <p>3rd order</p> Signup and view all the answers

    What is the primary focus of soil property when classifying soil types?

    <p>Major diagnostic horizon</p> Signup and view all the answers

    In the context of soil fertility, what property most directly affects plant growth?

    <p>Soil texture</p> Signup and view all the answers

    Which aspect of soil genesis refers to factors that affect soil formation?

    <p>Readily observable property</p> Signup and view all the answers

    What is the primary component that defines a soil 'series' in soil classification?

    <p>Basic unit of classification</p> Signup and view all the answers

    Which limitation is considered when assessing land suitability for tillage?

    <p>Physical barriers to rooting</p> Signup and view all the answers

    Which practice is most effective in reducing iron toxicity in soil?

    <p>Implement regular drainage during flooding conditions</p> Signup and view all the answers

    What is the primary function of micropores in soil?

    <p>To hold water available to plants</p> Signup and view all the answers

    Which factor is least likely to affect soil bulk density?

    <p>Topsoil thickness and color variations</p> Signup and view all the answers

    What is the primary consequence of applying gypsum (CaSO4) to sodic soils?

    <p>Improves soil structure by replacing sodium with calcium</p> Signup and view all the answers

    Which soil condition is primarily aggravated by high salinity content?

    <p>Decreased water availability for crops</p> Signup and view all the answers

    In which scenario would employing mulching be most beneficial?

    <p>To prevent soil erosion and conserve moisture</p> Signup and view all the answers

    Which property of soil is critically influenced by its texture?

    <p>Soil aeration and drainage capacity</p> Signup and view all the answers

    What can contribute significantly to the low levels of zinc availability in certain soils?

    <p>High iron content leading to competitive uptake</p> Signup and view all the answers

    Which treatment method is best used to improve phosphorus availability in soils?

    <p>Application of compost enriched with mycorrhizae</p> Signup and view all the answers

    What defines the condition of acid sulfate soils?

    <p>Low pH often near 4.0 due to sulfur oxidation</p> Signup and view all the answers

    Which soil type is typically associated with high organic matter suitability for pasture when conserved?

    <p>Histosol</p> Signup and view all the answers

    Which process describes the conversion of organic nitrogen back to inorganic forms in soil?

    <p>Denitrification</p> Signup and view all the answers

    Which horizon is characterized by significant accumulation of aluminum and iron oxides?

    <p>Argilic horizon</p> Signup and view all the answers

    What type of bacteria is primarily responsible for the solubilization of calcium phosphate in soil?

    <p>Pseudomonas</p> Signup and view all the answers

    Which soil classification describes a soil with a mean annual temperature that is categorized as hyperthermic?

    <p>Mollisol</p> Signup and view all the answers

    What process involves the reaction of carbonic acid with calcite to form calcium carbonate?

    <p>Carbonation</p> Signup and view all the answers

    Which type of soil parent material is characterized by having no movement?

    <p>Sedentary</p> Signup and view all the answers

    Which factor does NOT influence the chemical weathering of soils?

    <p>Soil texture</p> Signup and view all the answers

    In soil physics, what term is used to describe the process that leads to soil mixing by living organisms?

    <p>Bioturbation</p> Signup and view all the answers

    What does the term 'pedon' refer to in soil classification?

    <p>The basic unit of soil</p> Signup and view all the answers

    Which stage in soil formation is primarily characterized by the addition of organic material?

    <p>Organic matter addition</p> Signup and view all the answers

    Which mineral is associated with characteristics of heavy minerals in soil?

    <p>Hematite</p> Signup and view all the answers

    What represents the transition layer between two soil horizons?

    <p>AB layer</p> Signup and view all the answers

    Which level of soil survey involves delineation of areas less than or equal to 1 hectare and is most suitable for experiments or building sites?

    <p>1st order</p> Signup and view all the answers

    What are suborders in soil classification primarily based on?

    <p>Moisture and temperature regimes</p> Signup and view all the answers

    Which property is NOT categorized under the USDA soil taxonomy criteria?

    <p>Soil erosion potential</p> Signup and view all the answers

    Which order of soil survey is most extensive and reconnaissance in nature, covering areas of 16 to 252 hectares?

    <p>4th order</p> Signup and view all the answers

    In which level of soil classification is the 'great group' division focused?

    <p>Suborder</p> Signup and view all the answers

    What is the basic unit of soil classification emphasized in the taxonomy framework?

    <p>Series</p> Signup and view all the answers

    Which of the following factors does NOT typically influence land suitability classes?

    <p>Soil genesis</p> Signup and view all the answers

    What aspect does the 'family' classification in soil taxonomy specifically relate to?

    <p>Plant growth adaptations</p> Signup and view all the answers

    Which type of survey primarily focuses on regional planning aspects and covers the largest areas?

    <p>5th order</p> Signup and view all the answers

    Which of the following is a primary reason for conducting a soil survey?

    <p>To provide a comprehensive inventory of soil resources</p> Signup and view all the answers

    Which microbial group is most responsible for reducing sulfate to sulfide in soil?

    <p>Desulfovibrio</p> Signup and view all the answers

    What primarily affects the accumulation of soil organic matter (SOM)?

    <p>Temperature and moisture</p> Signup and view all the answers

    Which of the following best describes the characteristics of effective mycorrhizae in enhancing soil fertility?

    <p>Increasing phosphorus absorption</p> Signup and view all the answers

    Which component of soil organic matter typically experiences the highest rate of decomposition?

    <p>Cellulose</p> Signup and view all the answers

    Which factor is less likely to contribute to the decline of organic matter due to cultivation?

    <p>Enhanced plant growth</p> Signup and view all the answers

    In the context of soil chemistry, what is the molar mass of 1 cmol of calcium?

    <p>0.40 g</p> Signup and view all the answers

    Which type of mycorrhizae primarily forms an exterior mantle around plant roots?

    <p>Ectomycorrhiza</p> Signup and view all the answers

    What is a likely effect of flooding on soil nutrient dynamics?

    <p>Reduction of ferric phosphate</p> Signup and view all the answers

    What is the impact of composting on pathogen levels in organic materials?

    <p>Pathogens are destroyed during the thermophilic stage</p> Signup and view all the answers

    Which factor does NOT primarily contribute to the faster turnover of vegetative matter in grasslands compared to forests?

    <p>Higher moisture retention</p> Signup and view all the answers

    Which of the following methods is effective in addressing the problem of iron toxicity in flooded soils?

    <p>Install regular drainage to remove excess water</p> Signup and view all the answers

    In terms of soil texture, which size range does clay particles fall into?

    <p>Less than 0.002 um</p> Signup and view all the answers

    What is the preferred approach for managing sodic soils with high sodium content?

    <p>Apply gypsum to reclaim the soil</p> Signup and view all the answers

    Which of the following statements accurately describes micropores in soil?

    <p>They hold water and are crucial for plant moisture retention</p> Signup and view all the answers

    Which nutrient deficiency is characterized by brown or yellowish-brown colors in lowland soils?

    <p>Zinc deficiency</p> Signup and view all the answers

    What is the primary reason for applying organic fertilizers to acidic soils?

    <p>To provide micronutrients and improve fertility</p> Signup and view all the answers

    How can waterlogged conditions affect the breakdown of soil organic matter?

    <p>They lead to anaerobic conditions reducing decomposition rates</p> Signup and view all the answers

    What factor significantly influences bulk density measurements in soils?

    <p>Soil texture and moisture content</p> Signup and view all the answers

    Which technique is recommended for improving phosphorus availability in the soil?

    <p>Application of mycorrhiza-containing organic fertilizers</p> Signup and view all the answers

    What characteristic of saline soils necessitates careful irrigation management?

    <p>Presence of soluble salts that can accumulate</p> Signup and view all the answers

    Study Notes

    Soil Density

    • Sand has a higher bulk density (BD) than clay due to the larger particle sizes.
    • Bulk density is inversely proportional to organic matter content. This means that soils with higher organic matter content will have a lower bulk density.
    • Lower bulk density suggests better soil structure and higher porosity.
    • Higher organic matter content typically occurs on the soil surface.
    • BD is impacted by mechanical compaction and pedogenic processes.
    • Bedrock, parent material, and soil horizons (A, B, and C) are influenced by weathering events.

    Soil Formation

    • Soil forms through a multi-step process involving physical weathering, particle rearrangement, organic matter addition, chemical weathering, and soil horizon development.
    • Climate influences soil formation through temperature and rainfall.
    • Higher temperatures accelerate soil weathering and chemical reactions.
    • Rainfall encourages hydrolysis and hydration, leading to leaching and erosion.

    Five Factors of Soil Formation

    • Climate, living organisms, relief/topography, parent material, and time are the key factors impacting soil formation.

    Soil as a Medium

    • Soil underpins plant growth through a combination of inorganic and organic matter.
    • Soil is non-renewable, a natural body.
    • The soil surface is the upper boundary of the soil profile.
    • Soil is studied through several approaches focusing on fertility, physics, chemistry, microbiology, conservation and management, survey, and classification, mineralogy, and land use.

    Soil Components

    • Solid components include minerals and organic matter, comprising 45% and 5% of the soil.
    • Gaseous components include Nitrogen (78%), Oxygen (20%), and Carbon dioxide (0.5%).
    • Liquid components include water, ranging from 20-30%.

    Soil Pedon

    • Pedon is a horizontal slice of soil, encompassing an area of 1–10 square meters, representing the basic unit of soil.

    Soil Classification and Survey

    • Soil survey aims to inventory soil resources, usually at the provincial level.
    • Soil survey is categorized by scale, ranging from very intensive detailed for research or building projects to reconnaissance for regional planning.
    • The purpose of soil survey is to predict soil behavior, identify best-suited uses, and estimate productivity.

    Levels of Soil Classification

    • Soil classification is based on diagnostic horizons, moisture regimes, temperature regimes, and soil genesis.
    • Order is the highest level, followed by suborder, great group, subgroup, family, and series, with series representing the most basic classification unit.

    Land Suitability Classes

    • Soil suitability classes evaluate the suitability of land for different uses based on factors like erosion potential, wetness, tillage limitations, plant rooting depth, flooding impacts, and mycorrhizae.

    Microbial Sulphur Transformations

    • Microorganisms drive a range of sulphur transformations in soil, including:
      • sulfate uptake by plants
      • microbial decomposition of sulfur
      • oxidation of inorganic sulfur
      • reduction of sulfate to sulfide
      • oxidation of elemental sulfur

    Soil Organic Matter

    • Soil organic matter (SOM) comprises the carbon-containing compounds in soil and originates from plant decomposition.
    • SOM accumulation is influenced by factors such as temperature, moisture, texture, and cropping systems.
    • SOM is higher in grasslands than forests due to faster turnover of vegetative matter and a shorter grass life cycle.
    • Cultivation decreases SOM due to enhanced oxidation and microbial activity.

    Composting

    • Composting is a process of creating humus-like organic material.
    • Compost is the final product of composting and has a crucial role in enhancing soil quality.
    • Temperature is central to decomposition processes, as a thermophilic stage with temperatures ranging from 50 to 75 °C is needed to eliminate pathogens.
    • Different microorganisms contribute to cellulose decomposition, with Fungi playing a significant role as well as Bacteria.

    Soil Texture and Bulk Density (BD)

    • Sand has a BD between 1.20 - 1.80 g/cm3
    • Clay has a BD of 1.13 g/cm3
    • Compact soil has a higher BD
    • Low nutrition soils have a higher BD compared to high nutrition soils
    • High levels of Organic Matter (OM) result in a lower BD
    • Soil BD is related to soil compaction, which in turn is linked to soil texture and OM content

    Soil Formation Stages

    • Soil formation occurs in five stages:
      • Physical weathering
      • Particle rearrangement
      • OM addition
      • Chemical weathering
      • Soil Horizon formation

    Factors Affecting Soil Formation

    • Climate:
      • Temperature influences reaction rate, with higher temperatures leading to faster weathering.
      • Rainfall drives hydrolysis, hydration, leaching, and erosion.
    • Living Organisms: Cause bioturbation, which is the mixing of soil.
    • Relief/Topography: Affects water movement, influencing soil development.
    • Parent Material:
      • Sedentary: Parent material that remains in its original location.
      • Transported: Parent material that has been moved from its original location.
        • Alluvium: Sediment deposited by rivers.

    Soil Definition and Components

    • Soil: A medium for plant growth composed of inorganic mineral matter, organic matter, and water.
    • Soil is non-renewable.
    • Solid Components:
      • Minerals (45%): Include a variety of inorganic minerals.
      • Organic matter (5%): Consists of decomposed plant and animal residues.
    • Gas Components:
      • Nitrogen (N2) (78%)
      • Oxygen (O2) (20%)
      • Carbon Dioxide (CO2) (0.5%)
    • Liquid Component: Water (20-30%)

    Soil Study Approaches

    • Fertility: Studying the nutrient content and availability in soil.
    • Physics: Analyzing the physical properties of soil, like texture, structure, and density.
    • Chemistry: Investigating the chemical composition and reactions in soil.
    • Microbiology: Examining the micro-organisms inhabiting soil, including bacteria, fungi, and protozoa.
    • Conservation and Management: Focusing on sustainable practices for soil use and protection.
    • Survey and Classification: Mapping and categorizing soil types based on their properties.
    • Mineralogy: Studying the mineral composition of soil.
    • Land Use: Assessing soil suitability for different land use purposes.

    Soil Individuals

    • Pedon: The basic unit of soil, a hexagonal volume of soil typically ranging from 1 to 10 square meters.
    • Polypedon: Multiple pedons together.

    Soil Classification and Survey

    • Soil survey: An inventory of soil resources conducted by region.
    • Soil classification: A hierarchical system for organizing and categorizing soils based on their properties.
      • Levels of classification:
        • Order: Based on major diagnostic horizons.
        • Suborder: Division of orders by moisture and temperature regimes.
        • Great Group: Division based on the arrangement of horizons, etc.
        • Subgroup: Categorizing soils within the great group, including typic, intergrades, and transitional subgroups.
        • Family: Dividing soils based on their suitability for plant growth.
        • Series: The basic unit of soil classification.

    Soil Taxonomy

    • Based on the USDA soil survey, it considers:
      • Soil Properties
      • Readily observable properties
      • Soil properties that affect soil genesis

    Considerations for Land Suitability Classes

    • Erosion and Runoff: The potential for soil erosion and water runoff.
    • Wetness: The level of soil moisture and its impact on plant growth.
    • Limitations to Tillage and Plant Rooting: Physical constraints that limit soil cultivation and root depth.
    • Flooding: The frequency and duration of flooding.
    • Mycorrhiza: The presence of mycorrhizal fungi, which are beneficial to plant health.
      • Ectotrophic: Mycorrhiza that form a mantle outside of plant roots.
      • Endomycorrhiza: Mycorrhiza that penetrate plant cells.
    • Iron Toxicity: The presence of excessive iron, which can be toxic to plants.
    • Zinc Deficiency: The lack of sufficient zinc, which can limit plant growth.
    • Waterlogged Soil: Soil that is saturated with water for extended periods, restricting root growth and oxygen availability.
    • Dryland: Soil that experiences periods of drought.

    Soil Organic Matter (SOM)

    • The total amount of carbon-containing compounds in soil, including decomposed plant and animal residues.
    • Factors affecting SOM accumulation:
      • Temperature
      • Moisture
      • Texture
      • Cropping system
    • Composition of SOM:
      • Cellulose (15-60%)
      • Hemicellulose (10-30%)
      • Lignin (5-30%)
      • Water-soluble fraction (5-30%)
      • Protein
      • Fats, oils, waxes
    • Relationship between SOM and Moisture: Higher SOM leads to increased moisture retention.
    • SOM in Grasslands vs. Forests: Grasslands tend to have higher SOM due to faster turnover of vegetative matter and shorter grass life cycles.
    • SOM and Cultivation: Cultivation can decrease SOM due to enhanced oxidation and microbial activity.

    Soil Microorganisms - Key Roles

    • Bacteria:
      • Biomass: 2,000 kg/hectare of fertile soil
      • Types: Psychrophilic (cold-loving)
      • Decomposition: Can decompose lignin, cellulose, and gum.
      • Mycorrhiza: Assist in phosphorus absorption.
      • Heterotrophic and Aerobic: Primarily obtain energy from organic matter and require oxygen.
    • Fungi:
      • Biomass: 8,000 kg/hectare of fertile soil
      • Adaptation: Highly adaptable to various environments.
      • Decomposition: Break down lignin, cellulose, and gum.
      • Mycorrhiza: Aid in phosphorus absorption.
      • Heterotrophic: Obtain energy from organic matter.
    • Actinomycetes:
      • Biomass: 4,000 kg/hectare of fertile soil
      • Function: Break down and simplify organic compounds.
      • Characteristics: Intermediate between bacteria and fungi.
      • Antibiotics: Produce antibiotics.
    • Algae:
      • Biomass: 250 kg/hectare of fertile soil
      • Characteristics: Chlorophyll-bearing, photosynthetic organisms.
      • Host for Bacteria: Provide a habitat for bacteria.

    Microbial Sulfur Transformation

    • Sulfate Form: Available for plant uptake.
    • Microbial Decomposition of Sulfur: Breaks down organic sulfur compounds.
    • Sulfur Oxidation: Conversion of inorganic sulfur compounds, such as sulfide, thiosulfate, and elemental sulfur, to sulfate.
    • Sulfur Reduction: Conversion of sulfate to sulfide by bacteria like Desulfovibrii and Desulfotomaculum.
    • Iron Bacteria: Oxidize ferrous iron (Fe2+) to ferric iron (Fe3+).

    Iron Precipitation

    • Iron Reduction: Conversion of ferric iron (Fe3+) to ferrous iron (Fe2+).
    • Iron Precipitation: Ferric iron (Fe3+) precipitates out of solution, forming insoluble iron compounds.

    Compost and Composting

    • Composting: A process of creating humus-like organic materials by controlled decomposition.
    • Compost: The finished product of composting, characterized by a C/N ratio of 14:1 to 20:1.
    • Pathogen Destruction: Pathogens are eliminated during the thermophilic stage of composting (50-75 °C).

    Cellulose Decomposition

    • Fungi:
      • Aspergillus
      • Fusarium
      • Trichoderma
    • Bacteria:
      • Bacillus
      • Clostridium
      • Vibrio
      • Cytophaga (abundant in soil, straw, and manure)

    Chemical Properties of Soil

    • Acidity: A measure of the concentration of hydrogen ions (H+) in the soil solution.
    • Calcareous Soil: Soil with a high lime content.
    • Salinity: Soil with a high salt content, characterized by an electrical conductivity (EC) greater than 4 mmhos/cm.
    • Sodic Soil: Soil with an excessive amount of soluble sodium (Na content > 15% of cation exchange capacity [CEC]).
    • Iron Toxicity: Soil with an excessive amount of soluble iron, which can be toxic to plants.
    • Zinc Deficiency: Soil lacking sufficient zinc, which is essential for plant growth.
    • Waterlogged Soil: Soil that is saturated with water for extended periods, leading to anaerobic conditions.
    • Dryland: Soil that experiences periods of drought.

    Chemical Properties - Management and Solutions

    • Acidity:
      • Liming: Applying calcium carbonate (CaCO3), calcium oxide (CaO), calcium hydroxide [Ca(OH)2], or dolomitic limestone [CaMg(CO3)2] to increase soil pH.
      • Other Approaches: Using ashes, guano, phosphatic fertilizers, urea, compost, and rice hull ash.
    • Calcareous Soil:
      • Organic Fertilizer: Applying organic matter to improve soil structure and fertility.
      • Topsoil Replacement: Removing calcareous topsoil and replacing it with clay-rich soil.
    • Salinity:
      • Organic Matter/Fertilizer: Applying organic matter and fertilizers to improve soil drainage.
      • Irrigation and Drainage: Irrigating with low-salt water and ensuring adequate drainage to remove salts.
      • Foliar Fertilizers: Spraying plants with fertilizers containing micronutrients to compensate for nutrient deficiencies.
      • Gypsum (CaSO4): Applying gypsum to replace sodium with calcium, improving soil structure and reducing salinity.
    • Sodic Soil:
      • Gypsum (CaSO4): Applying gypsum to exchange sodium ions with calcium ions, reducing sodium levels.
      • Phosphatic Fertilizers and Guano: Applying these materials to improve soil structure and fertility.
      • Rice Hull Ash and Other Ashes: Using these materials to improve soil structure and fertility.
    • Iron Toxicity:
      • Regular Drainage: Maintaining good drainage to oxidize iron and reduce its toxicity under flooded conditions.
      • Phosphatic Fertilizers and Guano: Applying these materials to reduce iron toxicity.
      • Tolerant Rice Varieties: Planting rice varieties that are tolerant to high iron levels.
    • Zinc Deficiency:
      • Foliar Fertilizers: Spraying plants with zinc-containing fertilizers, like ZnSO4.
      • Seedling Dipping: Dipping rice seedlings in a solution of 2 tablespoons of ZnO per liter of water (2% ZnO solution).
      • Compost and Ammonium Sulfate: Using compost and ammonium sulfate to increase zinc availability in the soil.
    • Waterlogged Soil:
      • Drainage: Maintaining drainage to remove excess water and create an aerobic soil environment.
      • Drought-Tolerant Crops: Planting crops adapted to drought conditions.
      • Raised-Bed Technology: Creating raised beds to improve drainage and water management.
      • Horticulture-on-Dikes: Developing gardens on raised dikes to improve drainage and productivity.
      • Organic Fertilizers and Compost: Applying organic matter to improve soil water holding capacity and structure.
      • Mycorrhiza-Containing Fertilizers: Using fertilizers containing mycorrhiza to enhance phosphorus absorption and root development.
      • Drip Irrigation with Fertigation: Implementing drip irrigation and fertigation systems to efficiently deliver water and nutrients.
    • Dryland:
      • Organic Fertilizers and Compost: Improving soil water retention capacity and structure.
      • Mycorrhiza-Containing Fertilizers: Enhancing water absorption and resilience.
      • Drought-Tolerant Crops: Selecting crops that tolerate drought conditions.
      • Raised Bed Technology: Increasing drainage and water retention.
      • Drip Irrigation System with Fertigation: Optimizing water and nutrient delivery.

    Soil Pore Space

    • Micropores: Smaller pores responsible for holding water.
    • Macropores: Larger pores responsible for air circulation and root growth.

    Bulk Density (BD)

    • A measure of soil compaction calculated by dividing the mass of the soil by its volume.
    • Factors affecting BD:
      • Soil texture
      • Organic Matter (OM) content
      • Compaction
    • High BD: Indicates soil compaction, which can hinder root growth, reduce aeration, and limit water infiltration.
    • Low BD: Indicates loose soil that usually has better aeration, water retention, and root development.

    Soil Orders and Diagnostic Horizons

    • Entisol - Youngest soil; A: arable, no conservation; D: suited for pasture, but arable when conserved
    • Gellisol - Young; immature; D: suited for pasture, but arable when conserved
    • Histosol - Organic/ high OM; waterlogged; L: flat but wet/stony; for pasture/forestry
    • Mollisol - Fertile soil (grasslands); M: steep; eroded; shallow soil; for pasture
    • Andisol - Volcanic ash; N: steep; eroded; shallow soil; pastured if acidic
    • Mollic - soft, dark, basic & water saturated; illuvial accum.of Al & Fe & OM
    • Ochric - thin, light colored; illuvial horizon of clay
    • Plaggen - man-made, due to manure
    • Argilic - white clay; illuvial horizon of clay
    • Oxic - very weathered layer of Al & Fe & 1:1 Clay
    • Sombic - light-colored with low % base-saturation
    • Placic - thin, black to dark-red pan cemented by Fe

    Soil Temperature and Moisture Regimes

    • Pergelic - mean annual temp is -8oC - 15oC;
    • Thermic - MAT = 15oC - 22oC
    • Hyperthermic - MAT > 22oC
    • Aquic - saturated and moist ≥ 3 mos. because cold
    • Xeric - MAT = dry summer, wet winter

    Soil Properties and Suitability

    • Particle size: Sand = 2 – 0.05 um
    • Suitability:
      • A: arable, no conservation
      • D: suited for pasture, but arable when conserved
      • L: flat but wet/stony; for pasture/forestry
      • M: steep; eroded; shallow soil; for pasture
      • N: steep; eroded; shallow soil; pastured if acidic

    Soil Nitrogen Cycle

    • Immobilization: Inorganic N -> organic N
    • Nitrification: NH4+ --nitrosomonas--> NO2- --nitrobacter--> NO3-
    • Denitrification: NO3 -> N2, NO (Pseudomonas, Achromobacter, Bacillus, Micrococcus); largely inaerobic
    • Ammonification: OM -> NH3
    • Symbiotic N-fixation: Rhizobia in roots (N -> NH3)
    • Non-symbiotic N-fixation: Azotobacter in soil (N -> NH3)

    Soil Bacteria: Nutritional & Oxygen Based Classification

    • Based on Nutrition:
      • Heterotrophic: Eats OM
      • Autotrophic: Eats CO2, Inorganic matter
        • Photosynthetic: Requires Sunlight
        • Chemosynthetic: Eats chemicals
    • Based on O2 Requirement:
      • Aerobic: Requires oxygen
      • Anaerobic: Cannot live in oxygen
      • Facultative: Generally requires O2, but can live when not present
    • Based on Temperature:
      • Mesophilic:
      • Thermopilic:

    Soil Phosphorus Cycle

    • Solubilization of Calcium Phosphate by:
      • Bacteria: Pseudomonas, Mycobacterium, Bacillus, Micrococcus
      • Fungi: Penicillin, Fusarium, Aspergillus

    Soil Phosphorus Solubilization Causes:

    • Organic acid Prod’n:
    • ...

    Soil Texture and Bulk Density

    • Soil texture is categorized based on sand, silt, and clay particles
    • Soil texture is related to bulk density, which measures soil compaction
    • Bulk density is calculated by dividing the mass of dry soil by the total volume of the soil sample
    • Increasing soil compaction reduces pore space available for plant growth

    Bulk Density and Other Factors

    • Organic matter (OM) is inversely proportional to bulk density. High OM leads to lower bulk density
    • Bulk density is affected by soil texture and mineral content:
      • Fine-textured soils (clay) with higher mineral density have higher bulk density than coarser soils (sand)
      • Heavy minerals like magnetite, hornblende, and hematite contribute to higher bulk density

    Soil Formation Stages

    • Soil formation involves a series of stages:
      • Physical weathering: breakdown of parent material
      • Particle rearrangement: movement and distribution of weathered material
      • Organic matter (OM) addition: accumulation of decaying plant and animal material
      • Chemical weathering: alteration of soil minerals through chemical reactions
      • Soil horizon formation: development of distinct layers in the soil profile

    Factors Affecting Soil Formation

    • Five key factors influence soil formation:
      • Climate: Temperature and rainfall affect weathering rates and leaching processes
      • Living organisms: Bioturbation (mixing of soil) by organisms contributes to soil development
      • Relief/Topography: Slope and elevation influence water movement and erosion
      • Parent material: The source material of the soil dictates its initial composition
      • Time: Soil formation is a gradual process that happens over long periods of time

    Soil Survey and Classification

    • Soil survey is an inventory of soil resources conducted within a specific geographic area
    • It provides information for:
      • Predicting soil behavior
      • Identifying the best soil uses
      • Estimating productivity
      • Supporting research

    Levels of Soil Classification

    • Soil classification is hierarchical:
      • Order: Based on major diagnostic horizons
      • Suborder: Divisions within orders based on moisture and temperature regimes
      • Great group: Divisions within suborders based on arrangement of horizons, etc.
      • Subgroup: Typic, intergrade, and transitional variations within great groups
      • Family: Divisions based on properties that affect plant growth
      • Series: Basic unit of classification

    Considerations for Land Suitability Classes

    • Factors considered for land suitability:
      • Erosion and runoff
      • Wetness
      • Limitations to tillage and plant rooting

    Soil Taxonomy

    • Soil Taxonomy, based on the USDA system, uses the following criteria:
      • Soil properties
      • Readily observable properties
      • Properties that reflect soil genesis

    Reasons for Soil Taxonomy

    • To organize knowledge about soils
    • To understand relationships among different soil types

    Soil Component Breakdown

    • Soil is composed of solid, gas, and liquid phases:
      • Solid:
        • Mineral (45%)
        • Organic matter (5%)
      • Gas:
        • Nitrogen (78%)
        • Oxygen (20%)
        • Carbon dioxide (0.5%)
      • Liquid:
        • Water (20-30%)

    Microbial Sulfur Transformation

    • Sulfur transformations in the soil are crucial for plant uptake
    • Microorganisms play a vital role:
      • Fungi: Assist in phosphorus absorption, decompose lignin, cellulose, and gum; generally heterotrophic and aerobic
      • Actinomycetes: Break down organic compounds; produce antibiotics; intermediate between bacteria and fungi
      • Algae: Chlorophyll-bearing, good hosts for bacteria
      • Bacteria:
        • Sulfate reducing bacteria : reduce sulfate to sulfide
        • Sulfate oxidizing bacteria: oxidize elemental sulfur, sulfides, and thiosulfates
        • Iron bacteria: oxidize ferrous iron to ferric iron

    Iron Precipitation

    • Iron can precipitate in the soil, leading to iron toxicity
    • Iron reduction and precipitation occur under waterlogged conditions

    Compost and Composting

    • Composting is a process to create humus-like organic material
    • Compost: finished product with a C/N ratio of 14/1 to 20/1
    • Thermophilic stage (50-75oC) during composting destroys pathogens

    Cellulose Decomposition

    • Fungi and bacteria play a key role in cellulose decomposition
    • Common cellulose decomposers:
      • Fungi: Aspergillus, Fusarium, Trichoderma
      • Bacteria: Bacillus, Clostridium, Vibrio, Cytophaga

    Soil Organic Matter

    • Influenced by temperature, moisture, texture, and cropping systems
    • Carbon-containing compounds in the soil contribute to SOM
    • Higher SOM accumulation in grasslands due to faster vegetation turnover and shorter life cycles
    • Cultivation can decrease OM due to enhanced oxidation and microbial activity

    Chemical Properties of Soil

    • Acidic soil: low pH
    • Calcareous soil: high lime content
    • Saline soil: high salt content
    • Sodic soil: high sodium content

    Soil Salinity Management

    • Avoid using ammonium sulfate
    • Apply gypsum (CaSO4)
    • Use mulching with organic materials
    • Employ irrigation and drainage

    Soil Sodicity Management

    • Reclaim with gypsum (CaSO4)
    • Apply organic matter and fertilizers
    • Apply rice hull ash and other forms of ashes

    Iron Toxicity Management

    • Regular drainage to oxidize iron
    • Apply phosphatic fertilizers and guano
    • Use tolerant rice varieties

    Zinc Deficiency Management

    • Spray foliar fertilizers
    • Dip root seedlings in zinc sulfate solution
    • Use compost containing zinc

    Waterlogged Soil Management

    • Construct canals for drainage
    • Employ raised-bed planting technology
    • Use drought-tolerant crops
    • Apply organic fertilizers and compost
    • Use mycorrhiza-containing organic fertilizers

    Dryland Soil Management

    • Apply mulching with organic materials

    • Construct canals to catch water for plant use

    • Employ drip irrigation with fertigation

    • Use drought-tolerant crops### Soil Diagnostic Horizons

    • Mollic: Soft, dark, basic, water-saturated, with high organic matter content.

    • Ochric: Thin, light-colored layer with low organic matter content.

    • Plaggen: Anthropogenic horizon created by the addition of manure.

    • Argilic: Illuvial horizon enriched with clay and sometimes iron and aluminum.

    • Oxic: Highly weathered layer with high levels of iron and aluminum oxides.

    • Sombic: Light-colored horizon with low base saturation.

    • Placic: Thin horizon cemented with iron oxides, forming a hard pan.

    Subsurface Horizons

    • Argilic: Illuvial horizon characterized by accumulation of clay.
    • Oxic: Highly weathered layer with high levels of iron and aluminum oxides.
    • Sombic: Light-colored horizon with low base saturation, indicating leaching of essential nutrients.

    Soil Temperature Regimes

    • Pergelic: Mean annual soil temperature is below 8°C.
    • Gellisol: Mean annual soil temperature is between 8°C and 15°C.
    • Thermic: Mean annual soil temperature is between 15°C and 22°C..
    • Hyperthermic: Mean annual soil temperature is above 22°C..

    Soil Moisture Regimes

    • Aquic: Soil is saturated with water for at least 3 months due to high groundwater levels.
    • Xeric: Dry summers alternating with wet winters.

    Particle Size

    • Sand: 2-0.05 um in diameter

    Soil Suitability Classes

    • A: Arable land with no significant conservation concerns.
    • D: Suitable for pasture, but arable when conserved.
    • L: Flat but wet/stony; suitable for pasture/forestry.
    • M: Steep slopes, eroded, shallow soil; suitable for pasture.
    • N: Steep slopes, eroded, shallow soil; pastured if acidic.

    Soil Orders

    • Entisol: Youngest soil order, often immature with minimal development.
    • Gellisol: Soil characterized by permafrost.
    • Histosol: Soil with high organic matter content, often waterlogged.
    • Mollisol: Fertile soil developed under grasslands.
    • Andisol: Soil derived from volcanic ash, typically high in nutrients.

    Bacterial Nutrition and Processes

    • Heterotrophic: Obtain energy from organic matter (OM).
    • Autotrophic: Obtain energy from inorganic sources like CO2.
    • Photosynthetic: Use sunlight for energy.
    • Chemosynthetic: Obtain energy from chemical reactions.

    Bacterial Oxygen Requirements

    • Aerobic: Require oxygen for survival.
    • Anaerobic: Cannot live in the presence of oxygen.
    • Facultative: Can survive with or without oxygen.

    Bacterial Temperature Requirements

    • Mesophilic: Thrive in moderate temperatures (20-45°C).
    • Thermophilic: Prefer high temperatures (45-80°C).

    Important Bacterial Processes in Soil

    • Immobilization: Conversion of inorganic nitrogen to organic nitrogen.
    • Nitrification: Conversion of ammonium (NH4+) to nitrate (NO3-) by Nitrosomonas and Nitrobacter bacteria.
    • Denitrification: Conversion of nitrate (NO3-) to nitrogen gas (N2) and nitrous oxide (NO) by Pseudomonas, Achromobacter, Bacillus, and Micrococcus bacteria.
    • Ammonification: Breakdown of organic matter (OM) into ammonia (NH3).
    • Symbiotic N-fixation: Nitrogen fixation by rhizobia bacteria in legume roots.
    • Non-symbiotic N-fixation: Nitrogen fixation by Azotobacter in soil.

    Calcium Phosphate Solubilization

    • Solubilization: Breakdown of calcium phosphate into soluble forms by bacteria and fungi.

    Bacteria Responsible:

    • Pseudomonas
    • Mycobacterium
    • Bacillus
    • Micrococcus

    Fungi Responsible:

    • Penicillin
    • Fusarium
    • Aspergillus

    Inorganic Phosphate Solubilization

    • Causes:
      • Organic acid production
      • Other mechanisms

    Soil Composition

    • Soil is composed of mineral matter (45%), organic matter (5%), water (20-30%), and gases (78% Nitrogen, 20% Oxygen, 0.5% CO2)

    Bulk Density (BD)

    • Bulk density is a measure of soil compaction and is calculated by dividing the mass of dry soil by the total volume of the soil.
    • BD is affected by soil texture:
      • Sandy soils have a lower BD (1.20 – 1.80 g/cm3) than clay soils (1.13 g/cm3).
      • Soils with high organic matter content generally have lower BD.
    • BD is also affected by factors such as:
      • Management practices: compaction from tillage and heavy machinery
      • Soil structure: poor structure leads to higher BD
      • Organic matter content: higher OM tends to have lower BD

    Soil Texture

    • Soil texture refers to the relative proportions of sand, silt, and clay particles.
    • The size of a soil particle determines its textural class:
      • Sand: 2.0 – 0.05 mm (coarse, gritty)
      • Silt: 0.05 – 0.002 mm (smooth, powdery)
      • Clay: < 0.002 mm (sticky, plastic)

    Soil Formation

    • Soil formation is a slow and complex process, involving five key factors:
      • Climate: Temperature and rainfall influence weathering rates and leaching processes.
      • Living Organisms: Bioturbation (mixing of soil by organisms) is a major factor.
      • Relief/Topography: Slope affects water movement and erosion rates.
      • Parent Material: The original rock material influences soil composition.
      • Time: Soil formation takes a long time.

    Soil Horizons

    • Soil horizons are layers of soil that develop over time, each with unique characteristics:
      • A Horizon: Surface layer, rich in organic matter.
      • B Horizon: Subsoil, enriched with materials leached from the A Horizon.
      • C Horizon: Weathered parent material.
      • R Horizon: Unweathered bedrock.

    Soil pH

    • Soil pH is a measure of acidity or alkalinity.
    • Optimum pH range for plant growth is 5.5 to 7.0.
    • pH affects:
      • Nutrient availability: Nutrient uptake is optimal at a specific pH range.
      • Microbial activity: Microbial populations are sensitive to pH changes.

    Soil Organic Matter (SOM)

    • SOM is the totality of carbon-containing compounds in the soil, including organic matter from plant and animal residues.
    • Factors affecting SOM accumulation:
      • Temperature: Increased temperature enhances decomposition rates.
      • Moisture: Moisture is essential for microbial activity.
      • Texture: Clay soils tend to retain OM better than sandy soils.
      • Cropping system: No-till systems promote SOM accumulation.

    Microbial Groups in Soil

    • Soil is a complex ecosystem teeming with microorganisms which play crucial roles in decomposition, nutrient cycling, and soil structure.
    • Key microbial groups in soil:
      • Fungi: Decomposers, especially of lignin and cellulose, with a biomass of approximately 8,000 kg/HFS.
      • Actinomycetes: Decomposers, producing antibiotics, with biomass of approximately 4,000 kg/HFS.
      • Bacteria: Decomposers, essential for nutrient cycling, with biomass of approximately 2,000 kg/HFS.
      • Algae: Photosynthetic, providing organic matter, with biomass of approximately 250 kg/HFS.

    Soil Classification and Survey

    • Soil classification is a systematic approach to organize information about soils based on their properties, genesis, and observable characteristics.
    • It is essential for:
      • Understanding soil relationships: Identifying similarities and differences between soils.
      • Prediciting soil behavior: Understanding soil behavior and its effects on land use.
      • Identifying best uses: Determining the suitability of soils for specific purposes.
      • Estimating productivity: Assessing the potential for agricultural production.

    Soil survey

    • Soil survey is an inventory of soil resources. It involves mapping and describing soils in a specific area.
    • The purpose of soil survey:
      • Predict soil behavior
      • Identify best uses
      • Estimate productivity
      • Provide research data for agricultural and environmental management.

    Soil Classification in the Philippines

    • The Philippines' soil classification system is based on the USDA system and is further divided into the following levels:
      • Order: Based on major diagnostic horizons.
      • Suborder: Divides orders based on moisture and temperature regimes.
      • Great group: Division based on arrangement and other soil properties.
      • Subgroup: Typic, intergrades, transitional.
      • Family: Division based on characteristics relevant to plant growth.
      • Series: Basic unit of classification.

    Soil Conservation and Management

    • Soil conservation and management involve practices that protect soil resources from degradation, erosion, and decline in fertility.
    • This includes:
      • Minimizing tillage: Reduced tillage helps preserve soil structure, organic matter, and reduce compaction.
      • Crop rotation: Planting different crops in sequence helps control pests, diseases, and nutrient depletion.
      • Cover cropping: Growing non-cash crops between the main plantings helps prevent erosion, improve soil structure, and suppress weeds.
      • Conservation tillage: Maintaining a layer of residue on the soil surface to protect soil from wind and water erosion.
      • Organic farming: Promoting the use of organic inputs, such as compost and manure, to improve soil fertility, reduce pollution, and enhance soil health.

    Soil Salinity

    • Salinity refers to the presence of high concentrations of salts in the soil.
    • It creates challenges for plant growth by:
      • Reducing water availability: Salts can affect the osmotic pressure of water in the soil, making it difficult for plants to absorb water.
      • Affecting nutrient uptake: Salts can interfere with nutrient uptake, leading to deficiencies.
      • Causing toxicity: High salt levels can be toxic to plants.

    Soil Sodicity

    • Sodicity refers to the presence of high levels of sodium in the soil.
    • It can:
      • Lead to soil dispersion: Sodium can cause clay particles to disperse and form a dense layer, reducing water infiltration and drainage.
      • Decrease permeability: High sodium levels can reduce the ability of water to move through the soil, leading to waterlogging.
      • Cause crusting: Sodium can cause the soil surface to crust, making it difficult for seedlings to emerge.

    Soil Acidity

    • Soil acidity refers to the presence of high levels of hydrogen ions in the soil.
    • Soil pH influences the availability of nutrients, microbial activity, and plant growth.

    Soil Management Practices for Specific Conditions

    • There are various soil management practices to address specific issues such as acidity, salinity, sodicity, and waterlogging:
      • Acidic Soils: Apply lime (calcium carbonate) to neutralize soil acidity.
      • Saline Soils: Apply organic matter such as manure or compost, practice irrigation and drainage to flush out excess salts, and spray plants with foliar fertilizers containing micronutrients.
      • Sodic Soils: Add gypsum (calcium sulfate) to displace sodium from the soil.
      • Waterlogged Soils: Use drought-tolerant crops, apply organic fertilizers, and improve drainage with canals or raised-bed technology.
      • Iron Toxicity: Use tolerant rice varieties, apply phosphatic fertilizers, and minimize irrigation to reduce iron accumulation.
      • Zinc Deficiency: Spray plants with zinc fertilizers (Zinc sulfate) or dip seedlings in a Zinc solution.

    Compost and Composting

    • Composting is the process of creating humus-like organic materials from organic waste.
    • The finished product is called compost.
    • Compost has a C:N ratio of 14:1 to 20:1, indicating a balanced mix of carbon and nitrogen for beneficial microbial activity.
    • Composting involves heating the organic waste to thermophilic temperatures (50-75°C) which kill pathogens and accelerate decomposition.

    Soil Horizons

    • Mollic: Soft, dark, basic, high in water and organic matter, suitable for arable use with proper conservation practices
    • Argilic: Illuvial horizon of clay accumulation, can be white, can also have accumulations of Al & Fe, suited for pastures if conserved
    • Ochric: Thin, light colored, low in organic matter, suitable for pastures or forestry, can be flat, wet and/or stony
    • Plaggen: Man-made from manure, suitable for pasture, can be steep and eroded
    • Sombic: Light-colored with low base saturation, suitable for pasture
    • Placic: Thin, dark cement pan with Fe, suitable for pasture
    • Oxic: Very weathered layer of iron and aluminum, indicates old soils and hot, humid climates

    Soil Temperature Regimes

    • Pergelic: Mean annual temperature is below 8°C, suitable for the coldest environments
    • Gellisol: Mean annual temperature is between 8°C and 15°C, suitable for cold, moist environments
    • Thermic: Mean annual temperature is between 15°C and 22°C, suitable for temperate environments
    • Hyperthermic: Mean annual temperature is over 22°C, suitable for warm, tropical environments

    Soil Moisture Regimes

    • Aquic: Saturated and moist for at least three continuous months, suitable for wet environments
    • Xeric: Dry summers and wet winters, suitable for dry environments with a distinct wet season

    Soil Particle Size

    • Sand: 2-0.05 um, the largest component
    • Silt: 0.05-0.002 um, intermediate in size
    • Clay: Less than 0.002 um, the smallest, most reactive component

    Suitability Classes

    • Entisol: Youngest soil order, often immature and subject to change, may be suitable for pasture or forestry, but not arable
    • Gellisol: Young, cold, and moist with high organic matter, may be unsuitable for cultivation
    • Histosol: Very high organic matter content, often boggy or waterlogged, best suited for forestry due to high moisture retention
    • Mollisol: Fertile soil, generally well-drained and suitable for grasslands, often considered the “fertile” soil
    • Andisol: Derived from volcanic ash, often found in mountainous areas, generally fertile and suitable for pastures
    • A: arable: Suitable for cultivation
    • D: pasture: Suitable for pasture, but may not be arable without conservation
    • L: wet/stony: Suitable for forestry or pasture, not arable due to moisture and/or stone content
    • M: steep/eroded: May be suitable for pasture, but not arable due to slope
    • N: steep/shallow: May be suitable for pasture, but not arable due to slope and depth

    Soil Bacteria

    • Most important component of soil biota
    • Single-celled, aerobic, and reproduce via binary fission
    • Consume bacteria and organic matter
    • Biomass: 100 kg/HFS
    • Can be classified based on their relationship to organic matter, oxygen, and temperature

    Soil Bacterial Nutrition

    • Heterotrophic: Eat organic matter, critical for decomposing dead material and releasing nutrients
    • Autotrophic: Eat CO2 and inorganic matter, important for primary production and providing energy sources for other organisms
    • Photosynthetic: Utilize sunlight to convert inorganic matter into food, key for primary production in environments with light
    • Chemosynthetic: Use chemical energy (e.g., mineral oxidation) to produce food, common in environments without light

    Soil Bacterial Oxygen Requirements

    • Aerobic: Require oxygen for respiration
    • Anaerobic: Cannot live in oxygen-rich environments, important for nutrient cycling in oxygen-deprived environments
    • Facultative: Can survive with or without oxygen, providing flexibility in various environments

    Soil Bacterial Temperature Requirements

    • Mesophilic: Thrive at moderate temperatures, the majority of soil bacteria fall into this category
    • Thermophilic: Prefer high temperatures, important for environments with high heat

    Soil Nitrogen Cycle

    • Immobilization: Conversion of inorganic nitrogen (NH4+) to organic nitrogen (OM) by bacteria
    • Nitrification: Oxidation of ammonium (NH4+) to nitrate (NO3-) by bacteria:
      • Nitrosomonas: Converts NH4+ to NO2-
      • Nitrobacter: Converts NO2- to NO3-
    • Denitrification: Reduction of nitrate (NO3-) to nitrogen gas (N2) by bacteria:
      • Pseudomonas, Achromobacter, Bacillus, Micrococcus
    • Ammonification: Decomposition of organic matter (OM) to ammonia (NH3) by bacteria
    • Symbiotic N-fixation: Conversion of atmospheric nitrogen (N2) to ammonia (NH3) by bacteria living in the roots of plants, usually legumes:
      • Rhizobia: Nitrogen-fixing bacteria
    • Non-symbiotic N-fixation: Conversion of atmospheric nitrogen (N2) to ammonia (NH3) by free-living bacteria in the soil:
      • Azotobacter: Nitrogen-fixing bacteria

    Soil Phosphorus Cycle

    • Solubilization of Calcium Phosphate: Release of phosphorus from calcium phosphate minerals by bacteria and fungi:
      • Bacteria: Pseudomonas, Mycobacterium, Bacillus, Micrococcus
      • Fungi: Penicillin, Fusarium, Aspergillus

    Soil Phosphorus Solubilization Mechanisms

    • Organic acid production: Bacteria release acids that dissolve calcium phosphate and release phosphorus
    • Other unknown mechanisms: There are other ways that phosphorus is released from minerals that are not fully understood

    Soil Inorganic Phosphorus

    • Solubilization: The process of releasing inorganic phosphorus from mineral forms, crucial for making phosphorus available to plants
    • Causes:
      • Production of organic acids
      • Other unknown mechanisms

    Soil Texture and Bulk Density

    • Soil texture is determined by the proportions of sand, silt, and clay particles.
    • Sand particles are the largest (2.0 to 0.05 µm), feel coarse and gritty.
    • Silt particles are medium-sized (0.05 to 0.002 µm), feel smooth and powdery.
    • Clay particles are the smallest (< 0.002 µm) and have a sticky feel.
    • Bulk density (BD) measures soil compaction and is calculated as the mass of dry soil per unit volume.
    • BD is influenced by factors like soil texture, organic matter content, and tillage practices.

    Organic Matter and Bulk Density

    • Organic matter (OM) is inversely proportional to bulk density (BD).
    • High OM content typically leads to lower BD, as OM improves soil structure and aeration.
    • Conversely, low OM content contributes to higher BD, which can hinder root growth and aeration.

    Mineral Composition of Soils

    • Heavy minerals like magnetite, hornblende, zircon, and hematite are found in soil.
    • These minerals contribute to the bulk density of soil.
    • Weathering processes, like carbonation and dissolution, break down parent material, creating soil profiles.

    Stages of Soil Formation

    • Soil formation occurs through several distinct stages:
      • Physical weathering: breakdown of parent material by physical forces like temperature changes and freeze-thaw cycles.
      • Particle rearrangement: sorting and redistribution of weathered particles.
      • Organic matter addition: accumulation of dead plant and animal matter, contributing to soil fertility.
      • Chemical weathering: breakdown of minerals and organic matter through chemical reactions.
      • Soil horizon formation: development of distinct layers with different characteristics.

    Factors Affecting Soil Formation

    • Five key factors influence soil formation:
      • Climate: Temperature and rainfall play crucial roles in chemical weathering processes. Higher temperatures accelerate these reactions, while rainfall promotes leaching and erosion.
      • Living organisms: Plants and animals contribute to bioturbation (soil mixing), affecting soil structure and nutrient distribution.
      • Relief/topography: The shape of the land influences water movement, impacting erosion and nutrient distribution.
      • Parent material: The initial material from which soil develops can be sedentary (remaining in place) or transported by various agents like rivers (alluvium).
      • Time: Soil development is a slow process that takes many years, depending on the combined effects of these factors.

    Soil as a Medium for Plant Growth

    • Soil is essential for plant growth, providing physical support, water, and nutrients.
    • Soil is a non-renewable resource, taking thousands of years to form.
    • The uppermost layer of soil is called the soil surface.

    Soil as a Natural Body

    • A pedon is the basic unit of soil, representing a hexagonal soil body (1-10 m2).
    • A polypedon consists of multiple contiguous pedons.

    Approaches to Soil Study

    • Soil science employs various approaches to understand its complexity:
      • Fertility: nutrient availability and plant growth.
      • Physics: physical properties like texture and structure.
      • Chemistry: chemical composition and reactions.
      • Microbiology: microbial communities and activities within the soil.
      • Conservation and management: sustainable soil use and protection.
      • Survey and classification: mapping and categorizing soil types.
      • Mineralogy: mineral composition and their effect on soil properties.
      • Land use: suitability assessment for different purposes.

    Soil Components

    • Soil consists of four major components:
      • Solid: Minerals (45%) and Organic matter (5%).
      • Gas: Nitrogen (N2, 78%), Oxygen (O2, 20%), Carbon dioxide (CO2, 0.5%).
      • Liquid: Water (20-30%).

    Soil Survey

    • Soil survey is an inventory of soil resources conducted within a specific area, often at a provincial level.
    • It provides information on soil types, their distribution, and suitability for various uses.
    • The intensity of a soil survey varies depending on the purpose and scale.

    Levels of Soil Classification

    • Soil classification is hierarchical, beginning with broad orders and becoming increasingly specific:
      • Order: Based on the presence of major diagnostic soil horizons.
      • Suborder: Divides orders based on moisture and temperature regimes.
      • Great group: Characterized by the arrangement of soil horizons.
      • Subgroup: Further subdivides great groups into typic (typical), intergrades (transitional), and transitional subgroups.
      • Family: Defined by soil properties influencing plant growth.
      • Series: The basic unit of soil classification (approximately 400 series in the Philippines).

    Soil Taxonomy

    • Soil taxonomy, grounded in the USDA soil survey, classifies soil types based on:
      • Soil properties: physical, chemical, and biological characteristics.
      • Readily observable properties: easily identifiable features used for classification.
      • Soil property affects soil genesis: relationships between soil properties and their formation processes.

    Reasons for Soil Taxonomy

    • Soil taxonomy is important because:
      • It organizes knowledge about soils, allowing for clearer understanding.
      • It reveals relationships among different soil types, highlighting similarities and differences.
      • It assists in predicting soil behavior and determining best uses for various applications.

    Considerations for Land Suitability Classes

    • Land suitability assessments consider various factors to evaluate land use potential:
      • Erosion and runoff: susceptibility to soil loss and transport.
      • Wetness: presence of excess water affecting drainage.
      • Limitations to tillage and plant rooting: factors that hinder soil management or plant growth.
      • Flooding: duration and depth of flooding affecting root development.

    Chemical Properties of Soil

    • Soil chemical properties profoundly influence plant growth and soil health:
      • Acidity: soil pH level affecting nutrient availability.
      • Calcareous soils: high lime content, leading to higher pH.
      • Salinity: high salt content, potentially toxic to plants.
      • Sodic soils: high sodium content, affecting soil structure and water infiltration.
      • Iron toxicity: excessive iron levels in soil, especially under flooded conditions.
      • Zinc deficiency: inadequate zinc availability, impacting plant growth.
      • Waterlogged soils: saturated conditions leading to reduced oxygen availability and nutrient imbalances.
      • Dryland soils: characterized by low moisture levels and high nutrient losses through evaporation.

    Soil Organic Matter

    • Soil organic matter (SOM) is a critical component for soil fertility and health.

    • Its accumulation is influenced by factors like:

      • Temperature: higher temperatures accelerate decomposition rates.
      • Moisture: adequate moisture is vital for microbial activity and OM breakdown.
      • Texture: soil texture affects aeration and water holding capacity, influencing OM decomposition.
      • Cropping system: different practices impact OM levels, with grasslands generally accumulating more OM compared to forests.

    • OM is typically composed of:

      • Cellulose (15-60%): structural component of plant cells.
      • Hemicellulose (10-30%): complex carbohydrate found in plant cell walls.
      • Lignin (5-30%): complex polymer that provides rigidity to plant tissues.
      • Water-soluble fraction (5-30%): easily dissolved compounds like sugars and acids.
      • Proteins: nitrogen-containing molecules important for soil fertility.
      • Fats, oils, and waxes: organic compounds contributing to soil texture and water repellency.

    • SOM plays crucial roles in:

      • Improving soil structure and aeration.
      • Increasing water holding capacity.
      • Enhancing nutrient retention and availability.
      • Suppressing soilborne pathogens and diseases.

    Microbial Communities in Soil

    • The soil is teeming with diverse microbial communities, each playing specific roles in soil processes.
    • Key microbial groups include:

      • Fungi:

        • Biomass: 8,000 kg/HFS (hectare of forest soil).
        • Most adaptable to various conditions and important for decomposing lignin, cellulose, and gum.
        • Mycorrhizae: symbiotic relationships between fungi and plant roots, enhancing phosphorus absorption.
        • Heterotrophic and aerobic in nature.

      • Bacteria:

        • Biomass: 2,000 kg/HFS.
        • Play a crucial role in nitrogen fixation and decomposition.
        • Can decompose cellulose and lignin, releasing nutrients for plant growth.

      • Actinomycetes:

        • Biomass: 4,000 kg/HFS.
        • Intermediate between bacteria and fungi, breaking down complex organic compounds.
        • Produce antibiotics, contributing to disease suppression in soil.

      • Algae:

        • Biomass: 250 kg/HFS.
        • Chlorophyll-bearing organisms contributing to soil organic matter and providing a habitat for other microorganisms.

    Compost and Composting

    • Composting is the controlled decomposition of organic materials under aerobic conditions to create a nutrient-rich soil amendment.
    • Compost is the final product of composting, characterized by a C/N ratio of 14/1 to 20/1.
    • Pathogens are typically destroyed during the thermophilic stage (50–75 °C).
    • Cellulose decomposition is facilitated by both fungi and bacteria:
      • Fungi: Aspergillus, Fusarium, Trichoderma, and Cytophaga.
      • Bacteria: Bacillus, Clostridium, Vibrio, and Cytophaga.

    Microbial Sulfur Transformation

    • Sulfur is essential for plant growth, and its availability in soil is influenced by microbial transformations:
      • Sulfate form is the most readily available form for plants.
      • Mycorrhizae facilitate sulfate uptake by plants.
      • Desulfovibrii and Desulfotomaculum are bacteria that reduce sulfate to sulfide.
      • Oxidation of elemental sulfur leads to the formation of sulfuric acid.
      • Iron bacteria oxidize ferrous iron (Fe2+) to ferric iron (Fe3+).
      • Iron reduction processes contribute to iron precipitation.

    Soil Diagnostics

    • Mollic Horizon: Soft, dark, basic, and water-saturated. Illustrates accumulation of organic matter (OM) and base cations.
    • Ochric Horizon: Thin, light-colored, and low in organic matter.
    • Plaggen Horizon: Man-made horizon due to manure and other additions.
    • Argilic Horizon: Illuvial horizon of clay accumulation.
    • Oxic Horizon: Highly weathered layer with accumulation of aluminum, iron, and 1:1 clay minerals.
    • Sombic Horizon: Light-colored with low base saturation.
    • Placic Horizon: Thin, cemented pan of iron.

    Subsurface Horizons

    • Pergelic Temperature Regime: Mean annual temperature is less than 8°C. Soil is typically frozen for at least 3 months of the year.
    • Thermic Temperature Regime: Mean annual temperature is 15°C to 22°C.
    • Hyperthermic Temperature Regime: Mean annual temperature is greater than 22°C.
    • Aquic Moisture Regime: Soil is saturated with water for at least 3 months of the year.
    • Xeric Moisture Regime: Dry summers and wet winters.

    Soil Suitability Classes

    • Entisol: Youngest soil order.
      • A: Arable (suitable for farming) without conservation practices.
      • D: Suitable for pasture, but arable if conservation practices are implemented.
    • Gellisols: Young, immature soils.
      • D: Suitable for pasture, but arable if conservation practices are implemented.
    • Histosol: Organic soils with high organic matter content.
      • L: Flat but wet or stony. Suitable for pasture or forestry.
    • Mollisol: Fertile soils found in grasslands.
      • M: Steep, eroded, or shallow. Suitable for pasture.
    • Andisol: Soils derived from volcanic ash.
      • N: Steep, eroded, or shallow. Suitable for pasture if properly conserved.

    Soil Particle Size

    • Sand: 2-0.05 mm in diameter

    Soil Microorganisms

    • Bacteria: Single-celled, aerobic organisms.
      • Heterotrophic: Obtain energy from organic matter.
      • Autotrophic: Obtain energy from carbon dioxide and inorganic compounds.
      • Photosynthetic: Use sunlight as an energy source.
      • Chemosynthetic: Use chemicals as energy.

    Bacteria by Oxygen Requirement

    • Aerobic: Require oxygen for survival.
    • Anaerobic: Cannot live in the presence of oxygen.
    • Facultative: Can survive with or without oxygen.

    Bacteria by Temperature

    • Mesophilic: Optimal growth temperature is between 20°C and 45°C.
    • Thermophilic: Optimal growth temperature is between 45°C and 70°C.

    Soil Nitrogen Cycle

    • Immobilization: Inorganic nitrogen is converted to organic nitrogen.
    • Nitrification: Ammonia (NH4+) is oxidized to nitrate (NO3-).
      • Nitrosomonas: Convert NH4+ to nitrite (NO2-).
      • Nitrobacter: Convert NO2- to NO3-.
    • Denitrification: Nitrate is converted to nitrogen gas (N2) or nitrous oxide (N2O).
    • Ammonification: Organic matter is decomposed to ammonia (NH3).
    • Symbiotic Nitrogen Fixation: Rhizobia bacteria live in the roots of legumes and convert atmospheric nitrogen (N2) to ammonia (NH3).
    • Non-Symbiotic Nitrogen Fixation: Azotobacter bacteria in soil convert atmospheric nitrogen (N2) to ammonia (NH3).

    Soil Phosphorus Cycle

    • Solubilization of Calcium Phosphate:
      • Bacteria: Pseudomonas, Mycobacterium, Bacillus, Micrococcus
      • Fungi: Penicillin, Fusarium, Aspergillus
    • Causes of Solubilization:
      • Production of organic acids.

    Bulk density (BD)

    • Bulk density (BD) is a measure of soil compaction
    • BD = Ms/Vt
    • Sand has a BD between 1.20 – 1.80 g/cm3
    • Clay has a BD of 1.13 g/cm3
    • High BD is found in heavy mineral soil containing magnetite, hornblende, and zircon
    • High BD means lower pore density (PD)

    Soil Texture

    • Soil texture is determined by sand, silt, and clay content
    • Sand is coarse and gritty
    • Silt is smooth and powdery
    • Clay is compact, feels smooth, and is sticky when wet

    Soil Organic matter (SOM)

    • SOM is the totality of carbon-containing compounds in the soil
    • SOM is positively correlated with moisture
    • SOM is higher in grasslands than in forests due to a faster turnover of vegetative matter and a shorter grass life cycle
    • SOM declines with cultivation due to enhanced oxidation and microbial activity
    • SOM is made up of plant material:
      • Cellulose (15-60%)
      • Hemicellulose (10-30%)
      • Lignin (5-30%)
      • Water soluble fraction (5-30%)
      • Proteins
      • Fats, oil, wax

    Soil Pore Space

    • Soil pore space is made up of micropores and macropores
    • Micropores hold water
    • Macropores hold air for aeration and root growth
    • Macropores are necessary for good soil drainage and plant growth

    Soil Classification

    • Soil classification is based on the USDA soil survey
    • The Soil Taxonomy system uses readily observable properties and properties that are influenced by soil genesis
    • Order : highest level of classification, based on major diagnostic horizons
    • Suborder: Divides orders by moisture and temperature regimes
    • Great group: Divided by arrangement, etc
    • Subgroup: typic, intergrades, transitional
    • Family: division according to uses in plant growth
    • Series: basic unit
    • Soil series is the fundamental unit of classification, with over 400 series in the Philippines

    Soil Survey

    • A Soil survey is an inventory of soil resources
    • Soil surveys are completed at a province level
    • Soil surveys are used for:
      • Predicting soil behavior
      • Identifying the best uses of soils
      • Estimating productivity
      • Research

    Levels of Soil Survey

    • 1st level : very intensive, detailed; used for experiments and building sites; delineation of ≤1 ha
    • 2nd level: intensive, detailed; used for agriculture and urban planning; 0.6-4 ha
    • 3rd level: extensive; used for rangeland and community; 1.6-16 ha
    • 4th level: extensive, reconnaissance; used for broad land use; 16-252 ha
    • 5th level: exploratory; used regional planning; 252-4,000 ha

    Soil Genesis

    • Soil genesis is the process of soil formation
    • Stages of soil formation:
      • Physical weathering
      • Particle rearrangement
      • Organic matter addition
      • Chemical weathering
      • Soil Horizon formation
    • Parent material is an important factor in soil formation
      • Sedentary : Parent material has not moved
      • Transported : Parent material has moved: alluvial (river)
    • Carbonation and solution are important chemical weathering processes:
      • Carbonation: H2CO3 reaction (Calcite -> Calcium carbonate)
      • Solution: H2CO3/H+ dissociation (silica is dissolved)

    Factors Affecting Soil Formation

    • Climate:
      • Temperature: (10oC)T α (reaction)2
        • Tropical soils weather faster due to temperature
      • Rainfall: causes hydrolysis/hydration, leaching, and erosion
    • Living organisms: Cause bioturbation (soil mixing)
    • Relief/topography: Affects water movement
    • Parent material: See genesis under "Soil Genesis"
    • Time: It takes time to develop soil
    • Organisms: Important for OM decomposition
    • Relief/topography: Affects water movement

    Soil Use Considerations

    • Limitations:
      • Erosion/runoff
      • Wetness
      • Tillage and plant rooting
      • Flooding
      • Flooding can reduce ferric phosphate
    • Other considerations:
      • Mycorrhizae: help in phosphorus absorption, types include ectotrophic and endomycorrhizae
      • Microbial sulfur transformation:
        • Oxidation of inorganic sulfur: sulfide, thiosulfate, elemental S
        • Reduction of SO42-
        • Desulfovibrii & Desulfotomaculum: Reduces sulfate to sulfide

    Soil Microbiology

    • Fungi: Most adaptable, can decompose lignin, cellulose, and gum; biomass 8,000 Kg/HFS
    • Actinomycetes: Intermediate between bacteria and fungi; biomass 4,000 kg/HFS
    • Algae: Chlorophyll bearing, ideal host for bacteria; biomass 250 kg/HFS

    Soil Chemistry

    • Soil constituents have a chemical nature
    • Soil Acidity -Liming: Use CaCO3, CaO, Ca(OH)2, CaMg(CO3)2, ashes, guano, phosphatic fertilizer, urea, compost, and rice hull ash to improve soil pH
    • Calcareous Soild (High Lime Content): apply organic fertilizer, dig holes and replace with topsoil and clayey soils, spray plants with foliar fertilizers containing micronutrients (NPK), employ mulching, and use ammonium sulfate rather than urea
    • Saline soils (High Salt Content): Apply organic matter/fertilizer, irrigate and drain regularly to remove the salts, spray plants with foliar fertilizers containing important micronutrients, and apply gypsum (CaSO4)
    • Sodic Soils (High Sodium content): Reclaim using gypsum, apply phosphatic fertilizers and guano, apply rice hull ash and wood ash, use tolerant rice varieties to high levels of sodium, and use ammonium sulfate rather than urea
    • Iron Toxicity: Regular drainage to oxidize iron and reduce toxicity in flooded conditions.
    • Zinc Deficiency: Use foliar fertilizers containing zinc like ZnSO4, dip roots of rice seedlings in a 2% ZnO solution, apply adequate amounts of compost, and use ammonium sulfate rather than urea
    • Waterlogged Soils: Occasional drainage to increase the availability of zinc, construct canals to drain excess water, maintain well-drained soil, use drought tolerant crops, employ raised-bed technology, and apply organic fertilizers/compost to improve productivity.
    • Dryland Soils: These soils have nutrients in the oxidized state, apply organic fertilizers and compost to improve water retention, use drought-tolerant crops, employ raised-bed technology, and use drip irrigation with fertigation.

    Compost & Composting

    • Composting: A process used to create humus-like organic material from organic matter
    • Compost: The finished product of composting; C/N ratio: 14/1 – 20/1; pathogens are destroyed in the thermophilic stage of composting (50-75oC)
    • Cellulose decomposition: Fungi (Aspergillus, Fusarium, Trichoderma) and bacteria (Bacillus, Clostridium, Vibrio, Cytophaga) are involved in the decomposition of cellulose

    Chemical properties

    • Soil chemical properties are measured using cmol
    • 1 cmol = 1/1000 of a mole
    • 1 cmol Ca = 0.40g
    • 1 cmol H+ = 0.01 g

    Soil Diagnostic Horizons

    • Mollic: Soft, dark, basic, and water-saturated. Indicates high organic matter and base saturation.
    • Ochric: Thin, light-colored layer. Less organic matter and base saturation than Mollic.
    • Plaggen: Man-made horizon, high in organic matter due to the application of manure.
    • Argilic: Illuvial horizon of clay accumulation, indicates clay movement and translocation.
    • Oxic: Very weathered layer with high aluminum and iron oxides.
    • Sombic: Light-colored, low base saturation. Represents a significant loss of bases through weathering.
    • Placic: Thin, black to dark-red pan cemented by iron, a resistant layer often found in drier climates.

    Soil Subsurface Horizons

    • Argilic: Illuvial accumulation of clay.
    • Oxic: Illuvial accumulation of Aluminum and Iron oxides, indicative of intense weathering.
    • Sombic: Light-colored, low base saturation.
    • Placic: A resistant, cemented layer, often associated with iron oxides and/or calcium carbonate.

    Temperature Regimes

    • Pergelic: Mean annual temperature is below 8°C.
    • Gellisol: Mean annual temperature is between 8°C and 15°C.
    • Thermic: Mean annual temperature between 15°C and 22°C.
    • Hyperthermic: Mean annual temperature above 22°C.
    • Add "iso-": When there is a significant difference between summer and winter temperatures.

    Moisture Regimes

    • Aquic: Soil is saturated for at least 3 months during the growing season, resulting in high water content.
    • Xeric: Dry summers and wet winters are characteristic.

    Soil Particle Size

    • Sand: 0.05 mm – 2 mm.
    • Silt: 0.002 mm – 0.05 mm.
    • Clay: Less than 0.002 mm.

    Soil Order and Suitability

    • Entisol: Youngest soil order, often lacking horizons.
    • A: Arable, suitable for cultivation when adequately conserved.
    • D: Suited for pasture, but may be suitable for arable use when conserved.
    • L: Flat but wet or stony. Suitable for pasture or forestry.
    • Gellisol: Young, often found in cold climates.
    • Histosol: Organic soil, often high in water content. Requires careful management.
    • Mollisol: Fertile soil, commonly found in grasslands.
    • M: Steep, eroded or shallow, best suited for pasture.
    • Andisol: Volcanic ash soil, fertile but usually found in steep, eroded areas.
    • N: Steep, eroded, and shallow. Can be used for pasture if properly managed.

    Soil Nitrogen Cycle

    • Single-celled, aerobic bacteria: Play a vital role in nitrogen cycling.
    • Binary fission: Method of reproduction for bacteria.
    • Biomass: 100 kg per hectare of fertile soil.
    • Immobilization: Organic nitrogen is converted into inorganic nitrogen (NH4+).
    • Nitrification: NH4+ is oxidized to NO2- by Nitrosomonas, followed by NO2- to NO3- by Nitrobacter.
    • Denitrification: NO3- is converted to N2 and NO by Pseudomonas, Achromobacter, Bacillus, and Micrococcus in anaerobic conditions.
    • Ammonification: Organic matter is converted into NH3 by microorganisms.
    • Symbiotic nitrogen fixation: Rhizobia bacteria in legume roots convert nitrogen gas into ammonia.
    • Non-symbiotic nitrogen fixation: Azotobacter bacteria in soil convert atmospheric nitrogen into ammonia.

    Bacteria Types

    • Heterotrophic: Feed on organic matter.
    • Autotrophic: Feed on CO2 and inorganic matter.
    • Photosynthetic: Require sunlight.
    • Chemosynthetic: Derive energy from chemical reactions.
    • Aerobic: Require oxygen.
    • Anaerobic: Cannot live in oxygen.
    • Facultative: Can live in both aerobic and anaerobic conditions.
    • Mesophilic: Thrive in moderate temperatures.
    • Thermofilic: Live in high temperatures.

    Soil Phosphorus Cycle

    • Solubilization: Bacteria and fungi convert phosphorus in the soil into a plant-available form (inorganic phosphate).
    • Organic acid production: Leads to the solubilization of phosphorus, making it available to plants.
    • Pseudomonas: A genus of bacteria involved in solubilization.
    • Mycobacterium: A bacterial genus known for its role in phosphorus solubilization.
    • Bacillus: A genus of bacteria involved in phosphorus cycling.

    Soil Fungi

    • Penicillin: A genus of fungi important in phosphorus cycling.
    • Fusarium: A genus of fungi involved in phosphorus cycling.
    • Aspergillus: A genus of fungi known for its role in phosphorus mobilization.
    • Micrococcus: A genus of bacteria that plays a crucial role in phosphorus solubilization.

    Soil Texture & Bulk Density

    • Soil texture is determined by the relative proportion of sand, silt, and clay particles
    • Sand particles are the largest, followed by silt, and then clay
    • Clay particles are the smallest and have a diameter of less than 0.002 mm
    • Bulk density (BD) is a measure of soil compaction and is calculated by dividing the mass of the soil by its volume
    • Higher BD indicates denser packing of soil particles, which can limit root growth and water infiltration
    • A range of 1.20 – 1.80 g/cm3 is typical for sand, while clay typically has a BD of 1.13 g/cm3
    • The BD of soil can be influenced by factors such as the amount of organic matter, the presence of heavy minerals, and the degree of weathering

    Organic Matter & Bulk Density Relationship

    • There is an inverse relationship between organic matter (OM) and bulk density (BD)
    • This means that soils with higher OM content tend to have lower BD
    • OM helps to improve soil structure, which increases pore space and reduces compaction

    Soil Formation Stages

    • Soil formation is a complex process that involves several stages, including:
      • Physical weathering, which breaks down rocks into smaller particles
      • Particle rearrangement, which leads to the formation of soil layers
      • OM addition, which contributes to soil fertility
      • Chemical weathering, which alters the chemical composition of soil minerals
      • Soil horizon formation, which creates distinct layers within the soil profile

    Five Factors Affecting Soil Formation

    • Climate:
      • Temperature: Higher temperatures accelerate soil formation
      • Rainfall: Rainfall promotes hydrolysis, hydration, leaching, and erosion
    • Living Organisms:
      • Organisms contribute to bioturbation, which is the mixing of soil layers
    • Relief/Topography:
      • Topography influences water movement patterns, which can affect soil development
    • Parent Material:
      • Sedentary parent material is derived from rocks that have not been transported
      • Transported parent material originates from rocks that have been moved by various processes, including:
        • Alluvium: Transport by rivers
    • Time:
      • Soil formation is a slow process that can take thousands of years

    Soil Definition and Components

    • Soil is a natural body that is essential for plant growth
    • It is a mixture of inorganic and organic matter, including:
      • Solids:
        • Mineral matter (45%)
        • Organic matter (5%)
      • Gas:
        • Nitrogen (N2) (78%)
        • Oxygen (O2) (20%)
        • Carbon dioxide (CO3) (0.5%)
      • Liquid:
        • Water (20 - 30%)

    Approaches to Soil Study

    • Soil science encompasses various disciplines, including:
      • Fertility: Nutrient availability
      • Physics: Physical properties of soil, such as texture and structure
      • Chemistry: Chemical composition of soil, including pH and nutrient content
      • Microbiology: Microbial processes that occur in soil
      • Conservation & Management: Sustainable soil management practices
      • Survey & Classification: Mapping and classifying soil types
      • Mineralogy: Mineral composition of soil
      • Land Use: Suitability of soils for different land uses

    Soil Classification

    • Soil taxonomy is a hierarchical system of soil classification
    • It is based on the USDA soil survey and considers various factors, such as:
      • Soil properties
      • Readily observable properties
      • Soil properties that affect soil genesis
    • The hierarchical levels of classification include:
      • Order: Based on major diagnostic horizons
      • Suborder: Divides orders by moisture/temperature regime
      • Great group: Division based on arrangement of horizons
      • Subgroup: Typic, intergrades, transitional
      • Family: Division according to use in plant growth
      • Series: Basic unit of classification

    Land Suitability Classes

    • Soils are classified into land suitability classes to determine their suitability for different land uses
    • Considerations for land suitability classes include:
      • Erosion/runoff
      • Wetness
      • Limitations to tillage and plant rooting
      • Flooding
      • Mycorrhizae
        • Ectotrophic: Mycorrhizae form an external sheath on roots
        • Endomycorrhizae: Mycorrhizae penetrate plant cells

    Soil Microbial Communities

    • Soil microorganisms play a critical role in soil processes, including nutrient cycling and decomposition
    • Different microorganisms are involved in various transformations:
      • Bacteria
        • Psychrophilic bacteria: Can survive in cold temperatures
        • Biomass: 2,000 kg/HFS
        • Decompose lignin, cellulose, and gum
        • Mycorrhizae: Assist with phosphorus absorption
        • Heterotrophic and aerobic
      • Fungi:
        • Biomass: 8,000 kg/HFS
        • Most adaptable to different environments
        • Decompose lignin, cellulose, and gum
        • Mycorrhizae: Assist with phosphorus absorption
        • Heterotrophic and aerobic
      • Actinomycetes:
        • Biomass: 4,000 kg/HFS
        • Intermediate between bacteria and fungi
        • Attack and simplify organic compounds
        • Produce antibiotics
      • Algae:
        • Biomass: 250 kg/HFS
        • Chlorophyll-bearing
        • Excellent hosts for bacteria

    Soil Microbial Transformations of Sulfur

    • Microbial transformations of sulfur involve various oxidation and reduction processes:
      • Microbial decomposition of sulfur: Decomposers break down organic forms of sulfur, releasing sulfate available to plants
      • Sulfate reduction: Some bacteria, like Desulfovibrii and Desulfotomaculum, convert sulfate to sulfide
      • Oxidation of inorganic sulfur: Oxidation of sulfide, thiosulfate, and elemental sulfur leads to the formation of sulfate
      • Oxidation of ferrous iron: Iron bacteria oxidize ferrous iron (Fe2+) to ferric iron (Fe3+), which can contribute to iron precipitation

    Soil Chemical Properties

    • Soil chemistry refers to the chemical composition of soil and its impact on plant growth and development
    • Some important soil chemical properties include:
      • pH: A measure of soil acidity or alkalinity
        • Low pH (acidic) soils can inhibit plant growth and nutrient availability
        • High pH (alkaline) soils can also limit nutrient availability
      • Nutrient Content:
        • Macro-nutrients (N, P, K) are essential for plant growth and development
        • Micro-nutrients (Fe, Mn, Zn, Cu, B, Mo) are important in smaller quantities
      • Cation Exchange Capacity (CEC):
        • Refers to the soil's ability to hold and exchange positively charged nutrients
      • Soil Organic Matter (SOM):
        • SOM plays a crucial role in soil fertility, structure, and water retention
    • Acidity, Salinity, and Sodicity:
      • These are important chemical properties that can affect plant growth.

    Soil Acidification

    • Acidic soils can have a pH below 7, causing problems with nutrient availability and root growth
    • Acidic soils can be ameliorated by:
      • Liming with calcium carbonate (CaCO3), calcium oxide (CaO), calcium hydroxide (Ca(OH)2), or dolomite (CaMg(CO3)2
      • Applying organic fertilizer, ashes, or guano
      • Using urea instead of ammonium sulfate
      • Applying compost
      • Employing mulching
      • Using mycorrhiza-containing organic fertilizers
      • Deep plowing can help to bring up soil with a higher pH

    Calcareous Soils

    • Calcareous soils have a high content of calcium carbonate, resulting in a high pH
    • Amelioration of calcareous soils can involve:
      • Applying organic fertilizer
      • Digging holes and replacing the soil with topsoil and clayey soil
      • Spraying plants with foliar fertilizers containing micronutrients
      • Employing mulching with organic materials

    Salinity

    • Salinity refers to the presence of high levels of soluble salts in soils
    • Salinity can impede plant growth by decreasing water availability and increasing nutrient imbalance
    • Salinity can be managed by:
      • Applying organic matter or fertilizer
      • Digging holes and replacing soil
      • Irrigating and draining to leach excess salt
      • Employing mulching with organic materials
      • Using foliar fertilizers containing micronutrients
      • Applying gypsum

    Sodicity

    • Sodicity is a problem that arises from high levels of sodium in the soil
    • Sodium can cause soil particles to disperse, resulting in poor soil structure and reduced infiltration
    • Remediation of sodic soils involves:
      • Using gypsum (CaSO4) to replace sodium with calcium
      • Applying rice hull ash or wood ash
      • Applying phosphatic fertilizers or guano
      • Utilizing tolerant plant varieties

    Iron Toxicity

    • Iron toxicity can occur in waterlogged soils with excessive amounts of soluble iron
    • Iron-toxic soils can be addressed by:
      • Regular drainage
      • Using phosphatic fertilizers and guano
      • Applying rice hull ash or wood ash
      • Employing tolerant plant varieties

    Zinc Deficiency

    • Zinc deficiency can occur in soils with low pH and high levels of organic matter
    • Zinc deficiency can be addressed by:
      • Spraying foliar fertilizers containing zinc
      • Dipping roots of seedlings in a zinc solution
      • Using tolerant plant varieties

    Waterlogged Soils

    • Waterlogged soils are saturated with water, leading to anaerobic conditions that reduce the availability of essential nutrients and promote the accumulation of toxic compounds
    • Managing waterlogged soils involves:
      • Digging holes to serve as water catchments
      • Constructing canals for drainage
      • Employing mulching with organic materials
      • Utilizing drought-tolerant crops
      • Employing raised-bed technology
      • Employing drip irrigation technology

    Dryland Soils

    • Dryland soils have low water availability and may experience nutrient deficiencies
    • Managing dryland soils involves:
      • Applying organic fertilizers and compost
      • Utilizing mycorrhiza-containing fertilizers
      • Employing drought-tolerant crops
      • Utilizing mulching techniques
      • Constructing canals to prevent water evaporation
      • Employing drip irrigation technology

    Soil Organic Matter

    • Soil organic matter (SOM) is a vital component of soil, playing a crucial role in soil fertility, structure, and water holding capacity.
    • SOM is formed by the decomposition of plant and animal residues
    • The accumulation of SOM is affected by:
      • Temperature
      • Moisture
      • Soil texture
      • Cropping system
    • Higher SOM content is typical of grasslands compared to forests because grasslands have faster turnover of vegetative matter and a shorter grass life cycle
    • Cultivation practices can result in a reduction of SOM due to enhanced oxidation and increased microbial activity.

    Compost and Composting

    • Composting is a process that involves the controlled decomposition of organic matter into a humus-like material
    • Compost is a valuable soil amendment that can improve soil structure, fertility, and water holding capacity
    • Composting results in a finished product with a C/N ratio ranging from 14/1 to 20/1.
    • Pathogens are generally eliminated during the thermophilic composting stage, when temperatures reach 50-75 degrees Celsius

    Cellulose Decomposition

    • Cellulose is a major component of plant cell walls
    • It is decomposed by various fungi and bacteria including:
      • Fungi:
        • Aspergillus
        • Fusarium
        • Trichoderma
        • Cytophaga
      • Bacteria:
        • Bacillus
        • Clostridium
        • Vibrio
        • Cytophoga

    Micropore and Macropore Space

    • Soil pore space is divided into two main categories:
      • Micropores:
        • Smaller pores
        • Hold water
        • Can restrict air movement
      • Macropores:
        • Larger pores
        • Hold air
        • Are important for aeration and root growth

    Soil Pore Space and Bulk Density

    • Soil pore space is inversely related to bulk density (BD)
    • Higher BD indicates a lower volume of pore space, which can limit root growth and water infiltration.

    Soil Horizons

    • Mollic: Soft, dark, basic, high in water saturation, accumulates organic matter
    • Argilic: Illuvial horizon of clay accumulation
    • Ochric: Thin, light-colored layer, low in organic matter, weathered
    • Plaggen: Man-made, due to manure, high in organic matter
    • Oxic: Highly weathered layer of aluminum, iron, and clay
    • Sombic: Light-colored with low base saturation, low in organic matter
    • Placic: Thin, black to dark-red pan cemented by iron

    Temperature and Moisture Regimes

    • Pergelic: Mean annual temperature below 8°C
    • Gellisol: Always frozen for at least 3 months, due to cold temperatures
    • Thermic: Mean annual temperature between 15°C and 22°C
    • Hyperthermic: Mean annual temperature above 22°C
    • Aquic: Saturated with water for at least 3 months
    • Xeric: Dry summers and wet winters

    Soil Particle Size and Soil Orders

    • Sand: 2 to 0.05 micrometers
    • Entisol: Young soil, immature
    • Histosol: High organic matter, waterlogged
    • Mollisol: Fertile soil, grasslands
    • Andisol: Volcanic Ash

    Soil Suitability Classes

    • A: Arable, no conservation needed
    • D: Suited for pasture, arable with conservation
    • L: Wet/stony, best for pasture or forestry
    • M: Steep, eroded, shallow soil, for pasture
    • N: Steep, eroded, shallow soil, pasture if conserved

    Soil Microbes

    • Bacteria: Single-celled, aerobic, binary fission, consume other bacteria, important for nutrient cycling
    • Fungi: Decomposers, important for plant growth, break down organic matter, solubilize calcium phosphate

    Nitrogen Cycle

    • Immobilization: Inorganic nitrogen converted to organic nitrogen
    • Nitrification: Ammonium converted to nitrates
    • Denitrification: Nitrates converted to nitrogen gas
    • Ammonification: Organic matter converted to ammonia
    • Symbiotic N-Fixation: Rhizobium bacteria in plant roots convert nitrogen gas to ammonia
    • Non-symbiotic N-Fixation: Azotobacter bacteria convert nitrogen gas to ammonia

    Phosphorus Cycle

    • Solubilization: Conversion of insoluble phosphorus to soluble phosphorus by bacteria and fungi
    • Organic Acids: Produced by bacteria and fungi contribute to the solubilization of phosphorus

    Soil Texture and Bulk Density (BD)

    • Sand has a BD of 1.20 – 1.80 g/cm3.
    • Clay has a BD of 1.13 g/cm3.
    • Bulk Density (BD) is affected by :
      • Soil texture
      • Organic matter
      • Amount of compaction
    • Organic Matter (OM) is inversely proportional to Bulk Density (OM α 1/BD) -
      • This means: Higher OM, lower BD
      • Surface soil has higher OM, meaning lower BD.

    Soil Composition

    • Minerals (45%)
    • Organic matter (5%)
    • Gas (78% N2, 20% O2, 0.5% CO3)
    • Liquid (20-30% Water)

    Soil Formation

    • Stages:
      • Physical weathering
      • Particle rearrangement
      • Organic matter addition
      • Chemical weathering
      • Soil horizon formation

    Factors Affecting Soil Formation

    • Climate:
      • Temperature: 10oC increase, reaction rates double
      • Tropical soils weather faster due to higher temperatures.
      • Rainfall: causes hydrolysis, hydration, leaching and erosion.
    • Living organisms: cause bioturbation (mixing of soil).
    • Organisms:
      • Relief / Topography: affects water movement
      • Parent material:
        • Sedentary (no movement)
        • Transported:
          • Alluvium (river)

    Soil Terminology

    • Pedon: Basic unit of soil: hexagonal (1-10 m2)
    • Polypedon: Multiple pedons
    • Soil surface: Upper limit of the soil

    Approaches to Soil Study

    • Fertility
    • Physics
    • Chemistry
    • Microbiology
    • Conservation & Management
    • Survey & Classification
    • Mineralogy
    • Land Use

    Soil Classification and Survey

    • Soil survey: Inventory of soil resources:
      • Published by province
      • Provides information to:
        • Predict soil behavior
        • Identify best land uses
        • Estimate productivity
        • Support extensive research results

    Levels of Soil Classification

    • Order: Based on major diagnostic horizons
    • Suborder: Divides orders based on moisture and temperature regimes
    • Great group: Divided based on arrangement of soil horizons
    • Subgroup: Includes typic, intergrades, and transitional subgroups
    • Family: Divided according to characteristics affecting plant growth
    • Series: Basic unit of classification (400 series in the Philippines)

    Considerations for Land Suitability Classes

    • Erosion/Runoff:
    • Wetness:
    • Limitations to Tillage and Plant Rooting:
    • Flooding:
      • Reduces ferric phosphate
    • Mycorrhiza:
      • Ectotrophic: exterior mantle
      • Endomycorrhiza: penetrates cells
      • Assists in phosphorus absorption

    Chemical Properties of Soil

    • Acidity:
      • Liming: Using CaCO3, CaO, Ca(OH)2, or CaMg(CO3)2
      • Use of ashes
      • Application of guano or phosphatic fertilizer
      • Use of Urea rather than ammonium sulfate
      • Use of compost
      • Application of rice hull ash
      • Application of mycorrhiza-containing organic fertilizers to enhance phosphorus availability
    • Calcareous (High lime content):
      • Apply organic fertilizer
      • Dig holes and replace with topsoil and clayey soils
    • Salinity (High salt content):
      • Soil with toxic levels of soluble salts
      • Salinity is measured by Electrical Conductivity (EC): EC > 4 mmhos/cm
      • Management:
        • Apply organic matter/fertilizer
        • Irrigation and regular drainage to remove salts
        • Spray plants with foliar fertilizers containing micronutrients
        • Apply gypsum (CaSO4)
    • Sodic soils:
      • Excessive soluble sodium (Na content > 15% of CEC)
      • Reclaim using gypsum (CaSO4)
      • Apply phosphatic fertilizers and guano
      • Apply rice hull ash and other forms of ashes
      • Use tolerant rice varieties
      • Reduce soil compaction
    • Iron toxicity:
      • Excess iron in flooded conditions
      • Management:
        • Regular drainage to oxidize iron and reduce toxicity
        • Apply phosphatic fertilizers and guano
        • Use tolerant rice varieties
    • Zinc deficiency:
      • Management:
        • Spray foliar fertilizers containing zinc
        • Dipping rice seedlings in a 2% ZnO solution
    • Waterlogged soils:
      • Lowland/paddy soils
      • Characterized by anaerobic conditions with a thin oxidized layer
      • Management:
        • Regular drainage to increase oxygen availability
        • Construct canals to drain excess water
        • Use drought-tolerant crops
        • Employ raised-bed technologies
        • Apply organic fertilizers/compost
        • Apply mycorrhiza-containing organic fertilizers
        • Employ drip irrigation with fertigation
    • Dryland soils:
      • Nutrients present in oxidized state
      • Organic matter decomposition yields CO2
      • Management:
        • Apply mulch with organic materials to prevent moisture evaporation
        • Construct water catchment areas
        • Use drought-tolerant crops
        • Employ drip irrigation with fertigation

    Physical Properties of Soil

    • Soil texture: Determined by the relative proportions of sand, silt, and clay.
    • Soil separates:
      • Sand: 2.0- 0.05 mm, feels coarse and gritty
      • Silt: 0.05 - 0.002 mm, feels smooth and powdery
      • Clay: < 0.002 mm, feels sticky and plastic
    • Bulk Density (BD):
      • BD = Ms/Vt: Measures soil compaction
      • Factors affecting BD:
        • Soil texture
        • Amount of organic matter
        • Amount of compaction
    • Soil pore space:
      • Micropore: Holds water
      • Macropore: Holds air, important for aeration and root growth

    Soil Organic Matter (SOM)

    • Accumulation of SOM is affected by:
      • Temperature
      • Moisture
      • Texture
      • Cropping systems
    • SOM consists of:
      • Total carbon-containing compounds in soil
      • Organic constituents of plants
      • Components:
        • Cellulose: 15-60%
        • Hemicellulose: 10-30%
        • Lignin: 5-30%
        • Water soluble fraction: 5-30%
        • Protein
        • Fats, oils, and waxes.
    • SOM is proportional to moisture levels (SOM ∝ MOISTURE).
    • Grassland soil accumulates more OM due to faster turnover of vegetative matter and shorter grass life cycles.
    • Cultivation reduces OM due to increased oxidation and microbial activity.

    Compost and Composting

    • Composting: Creating humus-like organic materials
    • Compost: Finished product:
      • C/N ratio: 14/1- 20/1
      • Pathogens are destroyed during the thermophilic stage (50-750C)

    Cellulose Decomposition

    • Fungi: Aspergillus, Fusarium, Trichoderma.
    • Bacteria: Bacillus, Clostridium, Vibrio, Cytophaga

    Microbial Communities in Soil

    • Fungi:
      • Most adaptable
      • Can decompose lignin, cellulose, and gum
      • Mycorrhizae: assists in phosphorus absorption
      • Generally heterotrophic and aerobic
      • Biomass: 8,000 Kg/HFS
    • Actinomycetes:
      • Attack and simplify organic compounds
      • Intermediate between bacteria and fungi
      • Produce antibiotics
      • Biomass: 4,000 Kg/HFS
    • Bacteria:
      • Biomass: 2,000 Kg/HFS
      • Psychrophilic (cold-loving)
    • Algae:
      • Chlorophyll-bearing
      • Excellent hosts for bacteria
      • Biomass: 250 Kg/HFS

    Microbial Sulfur Transformation

    • Sulfate Form:
      • Available for plant uptake
      • Microbial decomposition of organic sulfur compounds
      • Oxidation of inorganic sulfur compounds (sulfide, thiosulfate, elemental sulfur)
    • Sulfide Form:
      • Desulfovibrii and Desulfotomaculum: Reduce sulfate to sulfide
    • Oxidation of Elemental Sulfur:
      • Leads to the formation of organic acids
      • Iron bacteria
        • Oxidize ferrous (Fe2+) to ferric (Fe3+) iron
    • Iron Precipitation:
      • Occurs during iron reduction
      • Can lead to formation of iron oxides

    Microbial Role in Nutrient Cycling

    • Nitrogen Fixation:
      • By nitrogen-fixing bacteria (e.g., Rhizobium).
    • Nitrification:
      • Conversion of ammonia (NH3) to nitrate (NO3-)
      • Important for nitrogen uptake by plants.
    • Denitrification:
      • Conversion of nitrate (NO3-) to dinitrogen gas (N2)
      • Can lead to nitrogen loss from the soil.

    Soil Fertility Management Practices

    • Lime:
      • Acid soils: Increases pH
      • Adds calcium, magnesium, and other nutrients
      • Improves soil structure
    • Organic matter:
      • Improves soil structure
      • Enhances water retention
      • Improves nutrient availability
      • Increases microbial activity
        • Soil organisms play a role in decomposition, nutrient cycling, and soil health.
      • Provides a source of nutrients.
    • Fertilizers:
      • Provides essential nutrients to crops
      • Can be organic or inorganic
    • Manures:
      • Derived from animal waste
    • Green manure:
      • Organic matter derived from plants
    • Crop rotations:
      • Involves planting different crops in a sequence
      • Helps maintain soil health
      • Improves nutrient cycling
      • Reduces pest and disease problems.

    Soil Conservation Practices

    • Crop rotations:
      • Promotes soil health by preventing nutrient depletion
      • Reduces pest and disease problems
    • Mulching:
      • Use of organic material to cover the soil surface.
      • Protects against erosion and reduces water loss
    • Contour farming:
      • Farming across the slope of the land.
      • Reduces water runoff and soil erosion.
    • Terracing:
      • Creation of level platforms on hillsides.
      • Reduces soil erosion
    • Windbreaks:
      • Plantings to shelter crops and reduce soil loss from wind erosion

    This information will help you to understand the concept of soil, its importance in agriculture, how it forms, how it is classified, and what are the key factors affecting its properties.

    Soil Horizons

    • Mollic: Soft, dark, basic, water-saturated, and rich in organic matter. Shows accumulation of illuvial, also known as secondary, horizons of clay, aluminum, iron, and organic matter.
    • Ochric: Thin, light-colored, and an accumulation of aluminum, iron, and 1:1 clay.
    • Plaggen: Man-made, formed by the addition of manure. Has a low base saturation.
    • Argilic: A horizon of clay accumulation, often with a white color.
    • Oxic: A horizon of extreme weathering with accumulation of iron, aluminum, and 1:1 clay.
    • Sombic: Light-colored, with low base saturation.
    • Placic: A thin, black to dark-red layer of iron-cemented fragments.

    Soil Temperature Regimes

    • Pergelic: Mean annual temperature is below 8°C. Soils remain frozen for more than 3 months.
    • Gellisol: Soil is moist for greater than 3 months.
    • Thermic: Mean annual temperature is between 15°C and 22°C.
    • Hyperthermic: Mean annual temperature of greater than 22°C.
    • Iso-: Additional modifier for temperature regimes that indicate a significant difference in temperature between summer and winter.

    Moisture Regimes

    • Aquic: Constantly saturated and often waterlogged.
    • Xeric: Dry summers and wet winters.

    Particle Sizes

    • Sand: 2 to 0.05 um
    • Silt: 0.05 to 0.002 um
    • Clay: < 0.002 um

    Soil Orders

    • Entisol: Youngest soil order.
    • Gellisol: Frozen soils with high organic matter.
    • Histosol: Highly organic soils with high decomposition activity. Waterlogged.
    • Mollisol: Fertile soil with high levels of organic matter, found in grasslands.
    • Andisol: Formed from volcanic ash.

    Soil Suitability Classes

    • A: Arable land, requiring no conservation practices.
    • D: Suited for pastures, but can be used for arable crops with conservation practices.
    • L: Flat, wet, or stony; Best suited for pasture, but can be used for forestry.
    • M: Steep, eroded, or shallow. Suited for pasture.
    • N: Steep, eroded, and shallow soil. Should be used for pasture if possible.

    Soil Microbial Groups

    • Bacteria: Single-celled, aerobic, and consume bacteria.
    • Heterotrophic: Bacteria that consume organic matter (OM).
    • Autotrophic: Bacteria that consume CO2 and inorganic matter.
    • Photosynthetic: Bacteria that use sunlight to obtain energy.
    • Chemosynthetic: Bacteria that consume chemicals for energy.
    • Aerobic: Bacteria that require oxygen.
    • Anaerobic: Bacteria that do not require oxygen, often live in waterlogged conditions.
    • Facultative: Bacteria that generally require oxygen but can survive in oxygen-deficient environments.
    • Mesophilic: Bacteria that thrive in moderate temperatures.
    • Thermophilic: Bacteria that thrive in high temperatures.

    Nitrogen Cycling

    • Immobilization: Inorganic nitrogen is converted to organic nitrogen.
    • Nitrification: The oxidation of ammonium (NH4+) to nitrate (NO3-) through the action of Nitrosomonas and Nitrobacter.
    • Denitrification: The reduction of nitrate to nitrogen gas (N2) and nitrous oxide (NO) by Pseudomonas, Achromobacter, Bacillus, and Micrococcus. Primarily occurs in anaerobic environments.
    • Ammonification: The decomposition of organic matter by bacteria, releasing ammonia (NH3).
    • Symbiotic N-fixation: The conversion of atmospheric nitrogen to ammonia by Rhizobia bacteria residing in the roots of legumes.
    • Non-symbiotic N-fixation: The conversion of atmospheric nitrogen to ammonia by Azotobacter bacteria found in soil.

    Phosphorus Cycling

    • Solubilization: The process of making inorganic phosphorus available to plants; can be achieved through the action of bacteria and fungi.

    Solubilizing Microorganisms

    • Bacteria: Pseudomonas, Mycobacterium, Bacillus, and Micrococcus.
    • Fungi: Penicillin, Fusarium, and Aspergillus.

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