Soil Science Answers PDF

Soil Science Answers 1. What is primarily examined in the first order of soil survey? A. Agricultural productivity B. General land use planning C. Broad reconnaissance of soil types D. Delineation for experiments and building sites Answer: Delineation for experiments and building sit...

Soil Science Answers 1. What is primarily examined in the first order of soil survey? A. Agricultural productivity B. General land use planning C. Broad reconnaissance of soil types D. Delineation for experiments and building sites Answer: Delineation for experiments and building sites (D) The first order of soil survey is very intensive and detailed, focusing on areas for experiments and building sites. 2. What is NOT a layer in the hierarchy of soil classification as described? A. Order B. Family C. Great group D. Type Answer: Type (D) The hierarchy includes order, great group, subgroup, family, and series, but not 'type'. 3. Which of the following is considered in land suitability classes? A. Soil nutrient quality B. Plant growth requirements C. Limitations to tillage and plant rooting D. Microclimate effects Answer: Limitations to tillage and plant rooting (C) Limitations to tillage and plant rooting are important considerations in assessing land suitability classes. 4. Which of these properties is NOT part of soil taxonomy based on USDA soil surveys? A. Soil property affects soil genesis B. Organic carbon content C. Soil property D. Readily observable property Answer: Organic carbon content (B) Soil taxonomy is based on observable properties, properties affecting genesis, and general soil properties, not specifically organic carbon content. 5. What is the primary purpose of organizing knowledge about soils? A. Develop new soil types B. Understand relationships among different soils C. Predict agricultural varieties D. Maximize soil erosion Answer: Understand relationships among different soils (B) Organizing knowledge about soils helps in understanding the relationships among different soil types. 6. Which factor is NOT directly associated with soil formation processes? A. Living organisms B. Nutrient absorption by plants C. Soil horizon formation D. Climate Answer: Nutrient absorption by plants (B) Nutrient absorption by plants occurs in established soil, but it does not directly contribute to the formation of soil. 7. What is the primary component of soil solids? A. Water B. Gases C. Organic matter D. Minerals Answer: Minerals (D) Minerals make up 45% of the solid components of soil, and organic matter constitutes only 5%. 8. During which stage of soil formation does chemical weathering occur? A. Soil horizon formation B. Physical weathering C. OM addition D. Particle rearrangement Answer: Soil horizon formation (A) Chemical weathering contributes to the development of soil horizons as minerals break down and alter the soil composition. 9. Which method is NOT an approach in soil study? A. Acid-base chemistry B. Microbiology C. Land use D. Survey & classification Answer: Acid-base chemistry (A) Acid-base chemistry is a specific aspect of soil chemistry, whereas the listed approaches represent broader fields of study. 10. What is a pedon in soil science? A. A method to classify soil B. A type of soil mineral C. The basic unit of soil measuring 1-10m2 D. A layer of soil horizon Answer: The basic unit of soil measuring 1-10m2 (C) A pedon is defined as the smallest unit of soil that can be characterized, measuring between 1 to 10 square meters. 11. Which soil texture is characterized by the highest bulk density? A. Silt B. Loam C. Clay D. Sand Answer: Sand (D) Sand typically has a bulk density ranging from 1.20 to 1.80 g/cm3, which is higher than that of clay and silt. 12. Which process is primarily driven by rainfall in soil formation? A. Soil horizon formation B. Chemical weathering C. Bioturbation D. Particle rearrangement Answer: Chemical weathering (B) Rainfall is crucial for chemical weathering as it facilitates hydrolysis, hydration, and other reactions that alter soil composition. 13. What is the primary reason tropical soils weather faster than other soils? A. Greater biodiversity B. Higher organic matter content C. Increased rainfall D. Warmer temperatures Answer: Warmer temperatures (D) Higher temperatures in tropical climates accelerate the rate of chemical reactions, thereby increasing the weathering rate of soils. 14. What component contributes most to the soil organic matter (SOM) accumulation in grasslands compared to forests? A. Faster turnover of vegetative matter B. Higher lignin content C. Longer grass life cycle D. Higher moisture availability Answer: Faster turnover of vegetative matter (A) Grasslands have a faster turnover of vegetative matter due to shorter grass life cycles, leading to more organic matter accumulation. 15. Which of the following is not a primary reason for the decline of organic matter (OM) due to cultivation? A. Higher moisture retention B. Enhanced oxidation C. Increased microbial activity D. Reduction of organic inputs Answer: Higher moisture retention (A) Moisture retention does not contribute to the decline in organic matter; in fact, it typically helps retain it. 16. Which fungus is associated with cellulose decomposition in composting? A. Aspergillus B. Vibrio C. Clostridium D. Bacillus Answer: Aspergillus (A) Aspergillus is one of the fungi known for its role in cellulose decomposition. 17. What is the typical carbon-to-nitrogen (C/N) ratio of finished compost? A. 14:1 to 20:1 B. 30:1 C. 10:1 D. 5:1 Answer: 14:1 to 20:1 (A) The C/N ratio of finished compost generally ranges from 14:1 to 20:1. 18. In soil chemistry, which ions have a molar mass representation of 1 cmol equal to 0.40 g for calcium? A. Sodium B. Calcium C. Magnesium D. Potassium Answer: Calcium (B) For calcium, 1 cmol is equal to 0.40 g, indicating its molar mass in soil chemistry. 19. What process helps in the microbial transformation of sulfate into sulfide? A. Chemical precipitation B. Oxidation of elemental sulfur C. Desulfovibrii activity D. Reduction of iron Answer: Desulfovibrii activity (C) The process carried out by Desulfovibrii converts sulfate into sulfide during microbial transformation. 20. What role do mycorrhizae predominantly play in soil fertility? A. Oxidizing organic matter B. Decomposing carbohydrates C. Assisting in nitrogen fixation D. Enhancing phosphorus absorption Answer: Enhancing phosphorus absorption (D) Mycorrhizae primarily assist plants in absorbing phosphorus from the soil. 21. Which component of soil organic matter is usually present in the highest percentage? A. Hemicellulose B. Lignin C. Water soluble fraction D. Cellulose Answer: Cellulose (D) Cellulose generally represents the largest fraction, usually around 15-60%, of soil organic matter. 22. Which of the following microbial groups is classified as ectotrophic mycorrhiza? A. External mantle fungi B. Aspergillus C. Rhizobacteria D. Desulfotomaculum Answer: External mantle fungi (A) Ectotrophic mycorrhizae are known for their external mantle, which surrounds the roots. 23. What is one result of flooding in soil management? A. Increased ferric phosphate B. Reduction of ferric phosphate C. Lowering moisture levels D. Enhanced microbial activity Answer: Reduction of ferric phosphate (B) Flooding can lead to reduced levels of ferric phosphate in the soil. 24. What is the primary contribution of rainfall to soil formation? A. Bioturbation and organic matter addition B. Sedimentation and mineralization C. Erosion and compaction D. Hydrolysis and leaching Answer: Hydrolysis and leaching (D) Rainfall accelerates processes like hydrolysis and leaching, which are crucial in soil formation. 25. Which factor significantly impacts the reaction rates during soil formation in tropical climates? A. Temperature B. Soil horizon availability C. Wind patterns D. Soil texture Answer: Temperature (A) Higher temperatures in tropical climates lead to faster chemical reactions during soil formation. 26. Which of the following is NOT a stage of soil formation? A. Chemical weathering B. Particle rearrangement C. Soil horizon formation D. Pollination Answer: Pollination (D) Pollination does not relate to soil formation processes. 27. What is the role of living organisms in the soil formation process? A. Increasing soil compaction B. Causing bioturbation C. Reducing mineral content D. Facilitating chemical bonding Answer: Causing bioturbation (B) Living organisms contribute to soil formation primarily through bioturbation, aiding in soil mixing. 28. Which of the following statements about soil classification is accurate? A. Soil horizon is irrelevant in classification. B. Soil classification ignores mineral composition. C. Soil classification is based on economic value only. D. Soil texture is a primary factor in classification. Answer: Soil texture is a primary factor in classification. (D) Soil texture is indeed a primary factor considered in soil classification. 29. How does organic matter (OM) generally affect soil characteristics? A. Reduces soil porosity B. Increases soil density C. Enhances nutrient retention D. Decreases water retention capacity Answer: Enhances nutrient retention (C) Organic matter enhances nutrient retention in the soil, improving fertility. 30. Which soil horizon represents the transition between soil layers? A. R horizon B. A horizon C. B horizon D. AB horizon Answer: AB horizon (D) The AB horizon represents a transitional layer between the A and B horizons. 31. Which of the following is a characteristic of heavy minerals found in soil? A. High chemical reactivity B. Non-persistent in soil C. Low density D. High magnetic susceptibility Answer: High magnetic susceptibility (D) Heavy minerals are often characterized by their high magnetic susceptibility. 32. What is a primary purpose of soil classification? A. To predict soil behavior and estimate productivity B. To categorize soil based on its location C. To determine the color of the soil D. To assess the history of the soil development Answer: To predict soil behavior and estimate productivity (A) Soil classification helps in predicting behaviors and estimating productivity by organizing knowledge about the soils. 33. In the hierarchy of soil classification, which level directly addresses moisture and temperature regimes? A. Suborder B. Great group C. Family D. Order Answer: Suborder (A) The suborder level divides the soil order based on moisture and temperature regimes. 34. Which level of soil survey would be most appropriate for regional planning? A. 4th B. 1st C. 5th D. 3rd Answer: 5th (C) The exploratory level of soil survey is most appropriate for regional planning, covering larger areas. 35. Which of the following is NOT a consideration for land suitability classes? A. Soil mineral composition B. Wetness C. Limitations to tillage and plant rooting D. Erosion and runoff Answer: Soil mineral composition (A) Soil mineral composition is not considered in the land suitability classes, which focus on physical conditions and limitations. 36. What is the basic unit in soil classification as outlined in the content? A. Series B. Family C. Great group D. Subgroup Answer: Series (A) The series is identified as the basic unit within the soil classification system. 37. Which of the following is a key property observed in soil taxonomy? A. Soil color B. Soil property affecting soil structure C. Soil management practices D. Soil genesis Answer: Soil genesis (D) Soil genesis is among the properties that are significant in soil taxonomy and its understanding. 38. Which order of soil survey is used primarily for detailed urban planning? A. 2nd order B. 4th order C. 1st order D. 3rd order Answer: 2nd order (A) The 2nd order of soil survey is the most intensive and is specifically used for urban planning. 39. What factor primarily influences the productivity of a specific soil type? A. Soil organic matter content B. Soil moisture content C. Soil color D. Soil temperature Answer: Soil organic matter content (A) Soil organic matter content is a critical factor influencing the productivity of soils. 40. What is the range of land area covered by the 3rd order of soil survey? A. 16-252 ha B. 0.6-4 ha C. ≤1 ha D. 1.6-16 ha Answer: 1.6-16 ha (D) The 3rd order of soil survey typically covers areas from 1.6 to 16 hectares. 41. What process primarily organizes knowledge about soils and their relationships? A. Soil fertility assessment B. Soil management C. Soil erosion D. Soil classification Answer: Soil classification (D) Soil classification is crucial for organizing knowledge about soils and understanding their interrelationships. 42. Which soil order is characterized by high organic matter and is suitable for pasture when conserved? A. Histosol B. Entisol C. Mollisol D. Andisol Answer: Histosol (A) Histosols are known for their high organic matter content, making them fertile and suitable for pasture. 43. What process describes the conversion of inorganic nitrogen into organic nitrogen in soil? A. Nitrification B. Immobilization C. Denitrification D. Ammonification Answer: Immobilization (B) Immobilization is the process where inorganic nitrogen is converted into organic forms by microorganisms. 44. Which of the following describes the soil temperature regime with a mean annual temperature of greater than 22°C? A. Pergelic B. Hyperthermic C. Thermic D. Mesophilic Answer: Hyperthermic (B) The hyperthermic temperature regime is characterized by a mean annual temperature exceeding 22°C. 45. What is the main characteristic of Agrilic soil horizons? A. Rich in organic matter B. Illuvial horizon of clay accumulation C. High content of volcanic ash D. Thin and light-colored Answer: Illuvial horizon of clay accumulation (B) Agrilic horizons are defined by the accumulation of clay, particularly white clay, in the illuvial horizon. 46. Which type of bacteria is primarily responsible for denitrification in soil, converting nitrates back to nitrogen gas? A. Rhizobia B. Nitrosomonas C. Azotobacter D. Pseudomonas Answer: Pseudomonas (D) Pseudomonas are one of the key groups of bacteria involved in denitrification, reducing nitrates to nitrogen gas. 47. What factor most significantly affects the accumulation of soil organic matter (SOM)? A. Topography B. Soil Color C. Soil pH D. Temperature Answer: Temperature (D) Soil organic matter accumulation is influenced primarily by temperature, moisture, texture, and cropping systems. 48. Which type of mycorrhizae primarily penetrates plant root cells? A. Endomycorrhiza B. Ectomycorrhiza C. Arbuscular mycorrhiza D. Vesicular-arbuscular mycorrhiza Answer: Endomycorrhiza (A) Endomycorrhizae penetrate the cells of the host plant, assisting in nutrient absorption. 49. What is the primary role of actinomycetes in soil? A. Attacking and simplifying organic compounds B. Fixing atmospheric nitrogen C. Absorbing water D. Decomposing lignin Answer: Attacking and simplifying organic compounds (A) Actinomycetes serve as intermediates between bacteria and fungi, attacking and simplifying organic materials. 50. Why does organic matter (OM) accumulate more in grasslands compared to forests? A. Faster turnover of vegetative matter B. Longer lifespan of trees C. Higher precipitation levels D. Less microbial activity Answer: Faster turnover of vegetative matter (A) Grasslands have a faster turnover of vegetative matter and shorter grass life cycles that contribute to higher OM accumulation. 51. In the context of composting, what is the typical C/N ratio? A. 14/1 to 20/1 B. 30/1 C. 25/1 D. 10/1 Answer: 14/1 to 20/1 (A) The C/N ratio of finished compost ranges from 14:1 to 20:1 to ensure proper decomposition. 52. What microbial process is responsible for reducing sulfate to sulfide? A. Fermentation B. Sulfur reduction C. Decomposition D. Sulfate oxidation Answer: Sulfur reduction (B) Desulfovibrio and Desulfotomaculum are examples of microbes that can reduce sulfate to sulfide. 53. What contributes to the enhancement of soil organic matter decline during cultivation? A. Enhanced oxidation and microbial activity B. Soil pH reduction C. Decreased soil temperature D. Increased rainfall Answer: Enhanced oxidation and microbial activity (A) Cultivation leads to increased oxidation and microbial activity, contributing to a decline in soil organic matter. 54. Which of the following processes occurs during thermophilic stages of composting? A. Pathogen destruction B. Lignin breakdown C. Nutrient leaching D. Water retention Answer: Pathogen destruction (A) During the thermophilic stage, temperatures reach between 50-75°C, which helps in the destruction of pathogens. 55. Which of the following is a component of soil organic matter (SOM) typically found in the greatest percentage? A. Water-soluble fraction B. Hemicellulose C. Cellulose D. Lignin Answer: Cellulose (C) Cellulose is generally the most abundant component, making up 15-60% of SOM. 56. What is a significant byproduct of microbial sulfur transformation in soils? A. Organic acids B. Nitrogen gas C. Carbon dioxide D. Phosphates Answer: Organic acids (A) Microbial transformations of sulfur lead to the production of various organic acids. 57. Which method can help mitigate iron toxicity in sodic soils? A. Deep plowing B. Apply organic fertilizers regularly C. Use of drought-tolerant crops D. Irrigation and regular drainage Answer: Irrigation and regular drainage (D) Irrigation and drainage help reduce the excess iron under flooded conditions, alleviating toxicity. 58. What is the primary benefit of liming with CaCO3 in acidic soils? A. Increase salinity levels B. Improve soil structure C. Enhance iron toxicity D. Neutralize soil acidity Answer: Neutralize soil acidity (D) Liming with calcium carbonate helps to neutralize the acidity in soils, improving conditions for plant growth. 59. Which of the following statements about soil pore space is correct? A. Micropores retain water for plants B. Macropores significantly limit root growth C. Micropores primarily hold air for aeration D. Macropores hold water for microbial activity Answer: Micropores retain water for plants (A) Micropores are essential for holding water, whereas macropores are crucial for air exchange and root growth. 60. What role do composts play in managing saline soils? A. Increase soluble salt content B. Suppress microbial activity C. Enhance soil fertility D. Increase the pH of the soil Answer: Enhance soil fertility (C) Composts help improve organic matter content and enhance nutrients, thereby helping in managing saline conditions. 61. Which factor is NOT likely to increase bulk density in soils? A. High organic matter content B. Drought conditions C. Soil compaction D. Heavy machinery use Answer: High organic matter content (A) High organic matter content tends to reduce bulk density by improving soil structure and porosity. 62. Which practice is beneficial for improving soil texture in lowland or paddy soils? A. Use of crystalline amendments B. Application of organic matter C. Incorporation of sand D. Frequent tillage Answer: Application of organic matter (B) Adding organic matter enhances soil texture by improving structure and water retention in lowland soils. 63. What is a common characteristic of sodic soils? A. High pH values B. High organic matter content C. Low sodium content D. Excellent drainage Answer: High pH values (A) Sodic soils often have high pH values due to the accumulation of sodium ions, affecting soil health. 64. Which practice may alleviate zinc deficiency in soils effectively? A. Use of urea as fertilizer B. Adding excessive organic matter C. Application of phosphorus fertilizers D. Spraying with foliar fertilizers containing zinc Answer: Spraying with foliar fertilizers containing zinc (D) Spraying plants with foliar fertilizers containing zinc directly improves zinc availability and alleviates deficiency. 65. What is the effect of waterlogging on soil conditions? A. Improves water drainage B. Leads to anaerobic conditions C. Promotes organic decomposition D. Enhances aeration Answer: Leads to anaerobic conditions (B) Waterlogging typically creates anaerobic conditions that can harm root health and soil biota. 66. Which property primarily influences the retention of nutrients and moisture in soils? A. Soil pH B. Soil texture C. Soil color D. Soil bulk density Answer: Soil texture (B) Soil texture directly affects how well the soil retains nutrients and moisture through its particle size distribution. 67. Which factor primarily influences particle rearrangement in soil formation? A. Temperature variations B. Parent material composition C. Water movement D. Biological activity Answer: Water movement (C) Water movement significantly affects how soil particles rearrange during the soil formation process. 68. What is the main function of the nutrient leaching process in soil? A. To increase soil compaction B. To remove excess nutrients and salts C. To promote organic matter decomposition D. To enhance mineral content Answer: To remove excess nutrients and salts (B) Nutrient leaching is primarily the process of removing excess nutrients and salts from the soil. 69. Which soil horizon forms right above the bedrock? A. Transition horizon B. Weathered parent material C. Subsoil D. Topsoil Answer: Transition horizon (A) The transition horizon is the layer that marks the change between soil horizons and bedrock. 70. In soil chemistry, what does carbonation primarily contribute to? A. Nutrient uptake by plants B. Formation of carbonates like calcium carbonate C. Development of soil horizons D. Soil erosion Answer: Formation of carbonates like calcium carbonate (B) Carbonation involves the formation of carbonates, significantly impacting soil composition. 71. Which approach in soil study analyzes the physical properties of soil? A. Physics B. Chemistry C. Survey and classification D. Microbiology Answer: Physics (A) The physics approach examines the physical properties affecting soil behavior and functions. 72. What primarily defines the bulk density of soil? A. Soil texture and structure B. Soil organic matter content C. Water retention capacity D. Leaching potential Answer: Soil texture and structure (A) The bulk density is influenced by both texture and structure, affecting soil compaction and porosity. 73. Which of the following is NOT a factor affecting soil formation? A. Parent material B. Human intervention C. Living organisms D. Climate Answer: Human intervention (B) While human intervention can affect soil, it is not considered a natural factor in soil formation. 74. What effect does organic matter generally have on soil characteristics? A. Decreases soil aeration B. Enhances soil fertility and water retention C. Increases soil acidity D. Reduces nutrient leaching Answer: Enhances soil fertility and water retention (B) Organic matter plays a crucial role in improving soil fertility and enhancing its water retention capacity. 75. What is the main purpose of soil taxonomy in soil study? A. To classify soils based on their economic value B. To document soil surveys without analysis C. To predict weather patterns based on soil characteristics D. To understand relationships among different soil types Answer: To understand relationships among different soil types (D) Soil taxonomy helps organize knowledge about soils and the relationships among various soil types. 76. Which of the following best describes the characteristics of the first order of soil survey? A. It delineates land areas smaller than one hectare. B. It covers extensive areas for agricultural studies. C. It is primarily used for broad land-use planning. D. It is for regional planning and cooperation. Answer: It delineates land areas smaller than one hectare. (A) The first order of soil survey is very intensive and detailed, specifically for areas smaller than one hectare. 77. Which level of soil classification directly addresses the arrangement of soil properties? A. Subgroup B. Family C. Great group D. Order Answer: Great group (C) The great group level divides soil classification by the arrangement of characteristics. 78. What factor is NOT typically considered in land suitability classes? A. Soil nutrient content B. Erosion/runoff C. Limitations to tillage and plant rooting D. Wetness Answer: Soil nutrient content (A) While wetness, erosion/runoff, and limitations to tillage and plant rooting are considered, soil nutrient content is not specifically listed. 79. Which type of soil survey is suited for agricultural and urban planning? A. First order B. Fourth order C. Third order D. Second order Answer: Second order (D) The second order of soil survey is intensive and detailed, ideal for agriculture and urban planning. 80. Which factor is associated with soil genesis and not a property of the soil itself? A. Climate conditions B. pH levels C. Particle size distribution D. Organic matter content Answer: Climate conditions (A) Climate conditions are external factors that influence soil genesis rather than inherent properties of the soil. 81. In soil classification, what is the basic unit referred to in the hierarchy? A. Suborder B. Family C. Great group D. Series Answer: Series (D) The series is considered the basic unit within the soil classification hierarchy. 82. What characteristic is typically used to differentiate soil orders? A. Geological parent material B. Diagnostic horizons C. Soil texture D. Moisture regime Answer: Diagnostic horizons (B) Soil orders are primarily organized based on major diagnostic horizons. 83. Which of the following soil properties is readily observable? A. Nutrient availability B. Microbial activity levels C. Organic matter decomposition rate D. Soil texture Answer: Soil texture (D) Soil texture is a readily observable property that can be identified without extensive testing. 84. Which order of soil survey primarily focuses on exploratory activities? A. Fourth order B. First order C. Second order D. Fifth order Answer: Fifth order (D) The fifth order of soil survey is exploratory and is used for regional planning. 85. What is the process by which inorganic nitrogen is converted into organic nitrogen in soil? A. Symbiotic N-fixation B. Nitrification C. Ammonification D. Denitrification Answer: Symbiotic N-fixation (A) Symbiotic N-fixation involves bacteria like Rhizobia in the roots of plants, converting atmospheric nitrogen into ammonia for the plant's use. 86. Which of the following soil temperature regimes has a mean annual temperature (MAT) of 15°C - 22°C? A. Peric B. Thermic C. Hyperthermic D. Mesic Answer: Thermic (B) The Thermic temperature regime is characterized by a MAT ranging from 15°C to 22°C. 87. Which soil order is typically associated with high organic matter, making it suitable for pasture when conserved? A. Entisol B. Andisol C. Mollisol D. Histosol Answer: Histosol (D) Histosols are characterized by high organic matter and are often waterlogged, making them suitable for pasture when managed properly. 88. Which factor does NOT significantly affect the accumulation of soil organic matter (SOM)? A. Moisture B. Temperature C. Soil color D. Soil texture Answer: Soil color (C) Soil color does not have a direct impact on the accumulation of soil organic matter. 89. What is the characteristic feature of an Argilic soil horizon? A. Illuvial horizon with clay accumulation B. Heavily weathered layer of Al and Fe C. Thin layer with low base saturation D. Rich in organic matter and nutrients Answer: Illuvial horizon with clay accumulation (A) The Argilic horizon is defined by the illuvial accumulation of clay, specifically white clay. 90. In the process of composting, what is generally destroyed during the thermophilic stage? A. Organic structure B. Carbon content C. Nutrient content D. Pathogens Answer: Pathogens (D) The thermophilic stage of composting is crucial for destroying pathogens. 91. Which process in soil chemistry primarily converts organic matter into ammonium? A. Nitrification B. Denitrification C. Ammonification D. Solubilization Answer: Ammonification (C) Ammonification is the process that converts organic matter into ammonia (NH3), primarily through microbial activity. 92. What is the primary role of fungi in the decomposition of organic matter? A. Nitrogen fixation B. Photosynthesis C. Carbon fixation D. Decomposition of lignin and cellulose Answer: Decomposition of lignin and cellulose (D) Fungi are essential for decomposing complex organic materials like lignin and cellulose. 93. Which group of microorganisms is primarily responsible for reducing sulfate to sulfide? A. Actinomycetes B. Acidobacteria C. Desulfovibrio and Desulfotomaculum D. Mycorrhizae Answer: Desulfovibrio and Desulfotomaculum (C) Desulfovibrio and Desulfotomaculum are key players in the reduction of sulfate to sulfide. 94. Which of the following percentages represents the typical composition of cellulose in soil organic matter? A. 5-30% B. 30-50% C. 15-60% D. 10-30% Answer: 15-60% (C) Cellulose typically composes 15-60% of the soil organic matter. 95. Which soil component most likely leads to enhanced oxidation and microbial activity when cultivation occurs? A. Soil organic matter B. Soil color C. Soil texture D. Soil compaction Answer: Soil organic matter (A) Soil organic matter declines due to enhanced oxidation and microbial activity from cultivation. 96. What type of mycorrhizae primarily helps in the penetration of plant root cells? A. Ectomycorrhiza B. Ectotrophic mycorrhiza C. Endomycorrhiza D. Arbuscular mycorrhiza Answer: Endomycorrhiza (C) Endomycorrhizae are known for penetrating plant root cells to assist in nutrient uptake. 97. Which organic component in soil is likely to have the highest percentage overall? A. Hemicellulose B. Lignin C. Cellulose D. Water soluble fraction Answer: Cellulose (C) Cellulose is generally present in the highest percentage among the listed organic components. 98. What is the typical carbon-to-nitrogen (C/N) ratio range for finished compost? A. 20/1 – 25/1 B. 5/1 – 10/1 C. 14/1 – 20/1 D. 10/1 – 15/1 Answer: 14/1 – 20/1 (C) The C/N ratio of finished compost typically falls between 14/1 and 20/1. 99. Which process is NOT associated with microbial metabolism of sulfur compounds? A. Transformation of nitrogen B. Oxidation of sulfide C. Conversion to thiosulfate D. Reduction of sulfate Answer: Transformation of nitrogen (A) The transformation of nitrogen is not a process directly related to the metabolism of sulfur compounds. 100. What amendment is recommended to counteract high salinity in soils? A. Use organic fertilizers B. Apply phosphatic fertilizers C. Irrigation and regular drainage D. Implement deep plowing Answer: Irrigation and regular drainage (C) Regular drainage helps remove excess salts from the soil, mitigating salinity issues. 101. Which organic fertilizer application method helps improve phosphorus availability in soils? A. Spray with aluminum sulfate B. Dig holes for drainage C. Apply mycorrhiza-containing organic fertilizers D. Use ashes Answer: Apply mycorrhiza-containing organic fertilizers (C) Mycorrhiza-containing fertilizers enhance the availability of fixed phosphorus for plant use. 102. What is a common soil texture that holds water in micropores? A. Silt B. Clay C. Loam D. Sand Answer: Clay (B) Clay texture has a high number of micropores which retain water. 103. Which factor significantly influences bulk density in soils? A. Temperature B. Soil color C. Organic matter content D. Salinity levels Answer: Organic matter content (C) The amount of organic matter in soil greatly affects its compaction and bulk density. 104. Which soil condition indicates a danger of iron toxicity? A. pH greater than 7 B. Soil EC greater than 4 mmhos/cm C. Sodium content exceeding 15% CEC D. Low available zinc Answer: Soil EC greater than 4 mmhos/cm (B) A higher soil electrical conductivity (EC) reflects an environment conducive to iron toxicity. 105. In which type of soil would you most likely need to implement methods to combat high iron concentration? A. Acid sulfate soils B. Sodic soils C. Calcareous soils D. Saline soils Answer: Acid sulfate soils (A) Acid sulfate soils often present high concentrations of iron due to low pH levels. 106. Which method is effective for managing waterlogged soils? A. Use ammonium sulfate B. Employ raised-bed technology C. Increase organic matter with compost D. Deep plowing Answer: Employ raised-bed technology (B) Raised-bed technology helps improve drainage and manages excess water in waterlogged conditions. 107. What nutrient deficiency is commonly addressed with foliar fertilizer applications? A. Nitrogen B. Phosphorus C. Potassium D. Zinc Answer: Zinc (D) Zinc deficiency is specifically addressed through foliar fertilizer applications containing zinc. 108. Which of these practices aids in the reduction of sodium levels in sodic soils? A. Irrigation and drainage B. Using wood ash C. Applying organic matter D. Spraying with urea Answer: Irrigation and drainage (A) Irrigation and regular drainage help to leach excess sodium from sodic soils. 109. What is the main role of calcium carbonate in soil management? A. Reduce acidity B. Increase salinity C. Increase moisture retention D. Enhance aeration Answer: Reduce acidity (A) Calcium carbonate is used in liming to increase soil pH and reduce acidity. 110. Which process involves the addition of organic matter during soil formation? A. OM addition B. Physical weathering C. Bioturbation D. Chemical weathering Answer: OM addition (A) Organic matter addition is a key phase in the soil formation process, enhancing the soil's fertility. 111. What primarily affects the bulk density of soil? A. Amount of rainfall received B. Type of vegetation present C. Soil pH level D. Soil texture and composition Answer: Soil texture and composition (D) Soil texture and composition directly influence the bulk density, as higher sand content typically leads to lower bulk density compared to clay. 112. In soil chemistry, how does the presence of H2CO3 affect mineral formation? A. It aids in carbonate dissolution. B. It contributes to leaching processes. C. It promotes physical weathering. D. It leads to organic matter decomposition. Answer: It aids in carbonate dissolution. (A) H2CO3 contributes to the dissolution of minerals, leading to the formation of calcium carbonate, a significant process in soil chemistry. 113. Which horizon represents the transition zone within a soil profile? A. A horizon B. B horizon C. C horizon D. AB horizon Answer: AB horizon (D) The AB horizon signifies a transition zone, where characteristics of both A and B horizons are present. 114. Which factor is known to accelerate the weathering process in soils? A. Increased vegetation cover B. Higher rainfall amounts C. Reduced microbial activity D. Lower temperatures Answer: Higher rainfall amounts (B) Higher rainfall increases hydrolysis and leaching, both of which accelerate soil weathering. 115. Which component constitutes the largest fraction of soil solids? A. Air B. Minerals C. Water D. Organic matter Answer: Minerals (B) Minerals make up approximately 45% of the total soil solids, constituting the largest proportion. 116. What effect does living organisms have on soil structure? A. Increase soil compaction B. Diminish soil fertility C. Reduce moisture retention D. Promote bioturbation Answer: Promote bioturbation (D) Living organisms contribute to bioturbation, enhancing soil structure and mixing layers. 117. Which of the following terms refers to the basic unit of soil classification? A. Pedon B. Layer C. Polypedon D. Profile Answer: Pedon (A) A pedon, a hexagonal area measuring 1-10 m², is considered the basic unit in soil classification. 118. Which of the following soil orders is characterized by the accumulation of organic matter and is suitable for pasture when conserved? A. Andisol B. Histosol C. Mollisol D. Entisol Answer: Histosol (B) Histosols are recognized for their high organic matter content and fertility, making them suitable for pasture when managed properly. 119. What process describes the conversion of organic nitrogen into inorganic nitrogen forms in soil via microbial activity? A. Denitrification B. Solubilization C. Nitrification D. Ammonification Answer: Ammonification (D) Ammonification is the process where organic nitrogen in decomposed matter is converted to ammonia, making it available for plants. 120. Which of the following temperature regimes indicates a mean annual temperature between 15°C to 22°C? A. Thermic B. Vergelic C. Mesophilic D. Hyperthermic Answer: Thermic (A) The Thermic regime is characterized by a median annual temperature ranging between 15°C and 22°C. 121. In soil chemistry, which microbial process is responsible for the transformation of ammonium to nitrite and then to nitrate? A. Mineralization B. Nitrification C. Nitrogen fixation D. Denitrification Answer: Nitrification (B) Nitrification is a key microbial process involving the oxidation of ammonium to nitrite, followed by the oxidation of nitrite to nitrate. 122. What is the primary characteristic of Oxic soil horizons? A. Presence of high organic matter B. Higher base saturation C. Very weathered layers of iron and aluminum D. Accumulation of illuvial clay Answer: Very weathered layers of iron and aluminum (C) Oxic horizons are highly weathered and characterized by a significant presence of iron and aluminum oxides. 123. What is the characteristic size range of the land covered by the 2nd order of soil survey? A. 1.6 to 16 hectares B. Less than 1 hectare C. 16 to 252 hectares D. 0.6 to 4 hectares Answer: 0.6 to 4 hectares (D) The 2nd order soil survey is detailed and typically covers areas from 0.6 to 4 hectares, useful for agriculture and urban planning. 124. Which level of soil classification divides the order by moisture and temperature regime? A. Subgroup B. Great group C. Suborder D. Order Answer: Suborder (C) The suborder is the classification level that specifically addresses differences in moisture and temperature regimes. 125. Which microorganism is primarily responsible for reducing sulfate to sulfide in the soil? A. Bacillus B. Aspergillus C. Cytophaga D. Desulfovibrii Answer: Desulfovibrii (D) Desulfovibrii is known for its role in the microbial transformation of sulfate to sulfide, which is important in sulfur cycling. 126. What is the main purpose of soil taxonomy as described? A. To determine economic value of soils B. To measure soil moisture levels C. To forecast soil erosion D. To organize knowledge about soils Answer: To organize knowledge about soils (D) The primary purpose of soil taxonomy is to organize knowledge about soils and understand the relationships among different types. 127. What is the typical carbon-to-nitrogen (C/N) ratio of compost before it is fully decomposed? A. 25/1 B. 30/1 C. 10/1 D. 14/1 – 20/1 Answer: 14/1 – 20/1 (D) The C/N ratio of compost before it is finished typically ranges between 14/1 and 20/1, which is crucial for efficient microbial activity. 128. Which soil survey order is intended primarily for very intensive studies, like building site evaluation? A. 3rd order B. 1st order C. 2nd order D. 4th order Answer: 1st order (B) The 1st order soil survey is the most detailed and is used for very intensive studies such as experiments and building site evaluations. 129. In terms of soil organic matter accumulation, which factor significantly contributes more to grasslands compared to forests? A. Faster turnover of vegetative matter B. Higher microbial activity C. Longer vegetation life cycle D. Greater moisture retention Answer: Faster turnover of vegetative matter (A) Grasslands have a faster turnover of vegetative matter due to shorter grasses, leading to more organic matter accumulation over time. 130. In terms of land suitability classes, which of the following is a notable consideration? A. Soil texture B. Limitations to tillage and plant rooting C. Soil color D. Historical land use Answer: Limitations to tillage and plant rooting (B) Limitations to tillage and plant rooting are among the specific considerations when evaluating land suitability classes. 131. Which of the following best describes ectotrophic mycorrhizae? A. They penetrate the plant root cells. B. They form an exterior mantle around roots. C. They primarily exploit cellulolytic activity. D. They assist in nitrogen fixation. Answer: They form an exterior mantle around roots. (B) Ectotrophic mycorrhizae are characterized by their formation of an exterior mantle around plant roots, aiding in nutrient uptake. 132. What is the effect of flooding on ferric phosphate in soil? A. It promotes precipitation of ferric phosphate. B. It enhances the oxidation of ferric ions. C. It reduces ferric phosphate availability. D. It increases the solubility of ferric phosphate. Answer: It reduces ferric phosphate availability. (C) Flooding typically reduces ferric phosphate availability, impacting nutrient dynamics within the soil. 133. What does the hierarchy of soil classification conclude with at the most granular level? A. Great group B. Subgroup C. Series D. Family Answer: Series (C) The series is considered the basic unit in soil classification, representing the most detailed level. 134. Which of the following factors is NOT listed as a concern for determining land suitability? A. Soil organic matter content B. Limitations to tillage C. Erosion/runoff D. Wetness Answer: Soil organic matter content (A) Soil organic matter content is not listed among the primary considerations for land suitability classes; the focus is on erosion, wetness, and tillage limitations. 135. Which chemical property of soil is indicated by the given equivalence of 1 cmol to 0.40 g for calcium? A. Hydraulic conductivity B. Saturation level C. Exchange capacity D. Molar mass representation Answer: Exchange capacity (C) The equivalence indicates the exchange capacity of the soil, which is crucial for nutrient retention and availability. 136. What does the term 'great group' refer to in soil classification? A. Division by arrangement and properties B. Major diagnostic horizons C. Selection for agricultural use D. Typic and intergrades Answer: Division by arrangement and properties (A) The 'great group' is categorized based on the arrangement of soil properties, which helps in distinguishing different soil types. 137. Which soil process is primarily associated with the microbial decomposition of organic materials like cellulose and hemicellulose? A. Iron reduction B. Composting C. Oxidation of sulfur D. Sorption and desorption Answer: Composting (B) Composting involves the microbial breakdown of organic materials, leading to the formation of humus-like substances. 138. Which factor most substantially affects the moisture content and thus the organic matter accumulation in soils? A. Soil type B. Precipitation patterns C. Land management practices D. Soil temperature Answer: Precipitation patterns (B) Precipitation patterns play a critical role in determining soil moisture content, which directly influences organic matter accumulation. 139. What is the main distinguishing characteristic of the 4th order soil survey? A. It is very detailed and intensive B. It covers broad land use with less detail C. It is limited to urban areas only D. It is exploratory in nature Answer: It covers broad land use with less detail (B) The 4th order soil survey is extensive and reconnaissance in nature, designed for broad land use assessments. 140. Which factor is primarily concerned with the genesis of soil and influences its formation? A. Color of the soil B. Soil texture C. Soil property D. Historical land use patterns Answer: Soil property (C) Soil property is directly concerned with soil genesis and plays a key role in influencing how soils are formed. 141. What is one characteristic differentiation of actinomycetes in the soil? A. They produce antibiotics. B. They are heterotrophic only. C. They primarily photosynthesize. D. They are anaerobic organisms. Answer: They produce antibiotics. (A) Actinomycetes are known for their ability to produce antibiotics, distinguishing them from other microbial groups in the soil. 142. Which component of soil organic matter typically contains the least percentage? A. Water soluble fraction B. Cellulose C. Lignin D. Hemicellulose Answer: Lignin (C) Among the components of soil organic matter, lignin typically represents the smallest percentage compared to cellulose and hemicellulose. 143. What is the recommended amendment to reduce iron toxicity in sodic soils? A. Use ammonium sulfate B. Dig holes and replace with top soil C. Spray foliar fertilizers containing micronutrients D. Apply gypsum (CaSO4) Answer: Apply gypsum (CaSO4) (D) Gypsum can help reclaim sodic soils by replacing sodium with calcium, thereby reducing iron toxicity. 144. Which soil texture holds water in micropores and supports root growth? A. Silt B. Clay C. Gravel D. Sand Answer: Clay (B) Clay has a higher micropore content, which holds more water, essential for root growth. 145. What is the primary function of using organic matter in managing high salinity soils? A. Facilitate drainage B. Increase nutrient availability C. Improve soil aeration D. Reduce soil pH Answer: Increase nutrient availability (B) Organic matter enhances nutrient availability and microbial activity, which helps manage salinity. 146. Which statement about dryland soil management is correct? A. Drought-tolerant crops do not require organic fertilizers B. Waterlogged conditions enhance crop growth C. Employing raised-bed technology increases water retention D. Irrigation is the only solution for moisture improvement Answer: Employing raised-bed technology increases water retention (C) Raised-bed technology helps in retaining moisture in dryland conditions. 147. What is one of the factors affecting bulk density in soils? A. Soil color B. Soil texture C. Soil pH D. Soil depth Answer: Soil texture (B) Soil texture significantly influences the bulk density due to different particle arrangements. 148. How can lowland or paddy soils be managed to address zinc deficiency? A. Utilize raised-bed technology B. Employ deep plowing methods C. Use ammonium sulfate as the main nutrient source D. Apply phosphatic fertilizers Answer: Apply phosphatic fertilizers (D) Applying phosphatic fertilizers can increase zinc availability in lowland soils. 149. Which approach is recommended to reduce acidity in soils? A. Use ammonium sulfate B. Liming using CaCO3, CaO, or Ca(OH)2 C. Irrigate regularly D. Apply organic fertilizers only Answer: Liming using CaCO3, CaO, or Ca(OH)2 (B) Liming with calcium compounds effectively raises soil pH and reduces acidity. 150. Which of the following is a characteristic of soils affected by iron toxicity? A. Brown, yellowish brown, red brown B. Dark, bluish gray color C. Light brown color D. Uniform black color Answer: Brown, yellowish brown, red brown (A) Soils affected by iron toxicity typically exhibit brown, yellowish brown, and red brown hues. 151. Which method can help alleviate conditions of waterlogged soils? A. Construct canals for drainage B. Use high-sodium irrigation water C. Spray foliar fertilizers D. Apply rice hull ash Answer: Construct canals for drainage (A) Constructing canals helps to drain excess water and maintain well-aerated soil conditions. 152. What is a common result of organic matter decomposition in waterlogged soils? A. Greater soil structure stability B. Increased CO2 levels C. Decreased nutrient availability D. Lowered acidity Answer: Increased CO2 levels (B) Decomposition in anaerobic conditions often leads to increased CO2 and possibly other gases like methane. 153. Which process involves the reaction of H2CO3 that leads to the formation of calcium carbonate? A. Bioturbation B. Hydrolysis C. Erosion D. Carbonation Answer: Carbonation (D) Carbonation is a chemical process that involves the reaction of carbonic acid with minerals, leading to the formation of compounds like calcium carbonate. 154. What is the primary soil component responsible for the majority of soil's inorganic structure? A. Gases B. Organic matter C. Minerals D. Water Answer: Minerals (C) Minerals make up approximately 45% of the soil's solid components, providing the bulk and structure to the soil. 155. Which of the following factors is NOT part of the five factors affecting soil formation? A. Relief/topography B. Production of organic compounds C. Climate D. Parent material Answer: Production of organic compounds (B) The five factors affecting soil formation include climate, living organisms, relief/topography, parent material, and time. 156. In which stage of soil formation does organic matter (OM) addition occur? A. Chemical weathering B. Soil horizon formation C. Particle rearrangement D. Physical weathering Answer: Particle rearrangement (C) Organic matter addition occurs as soils develop and incorporate biological material, typically after physical rearrangement. 157. What does the pedon represent in soil classification? A. A type of soil organism B. A larger regional area of soil C. A basic unit of soil D. A specific mineral component Answer: A basic unit of soil (C) A pedon is defined as the basic unit of soil, typically representing an area of 1- 10 m². 158. Which method is commonly used to determine soil texture? A. Hydrometer/pipette B. Soil classification C. Soil survey D. Microscopy Answer: Hydrometer/pipette (A) The hydrometer and pipette methods are standard laboratory techniques used to assess soil texture. 159. Which component of soil gas primarily influences the soil's aeration? A. Water vapor B. N2 C. O2 D. CO2 Answer: O2 (C) Oxygen (O2) is crucial for soil aeration and is essential for the respiration of soil organisms. 160. What role does bioturbation play in soil formation? A. It leads to particle rearrangement. B. It prevents hydrological erosion. C. It contributes to soil horizon stabilization. D. It enhances chemical weathering. Answer: It leads to particle rearrangement. (A) Bioturbation involves the movement and mixing of soil particles by organisms, aiding in soil structure and composition. 161. Which soil order is characterized by arable suitability and has no conservation potential? A. Entisol B. Histosol C. Mollisol D. Andisol Answer: Entisol (A) Entisol is classified as the youngest soil order and is typically not suited for conservation. 162. What process involves the conversion of organic nitrogen back into inorganic nitrogen compounds in the soil? A. Symbiotic N-fixation B. Denitrification C. Nitrification D. Ammonification Answer: Denitrification (B) Denitrification is the microbial process that converts nitrates back to nitrogen gas. 163. Which type of soil horizon is characterized by a thick illuvial accumulation of clay, aluminum, iron, and organic matter? A. Ochric B. Oxic C. Mollic D. Argilic Answer: Argilic (D) Argilic horizons are known for their illuvial accumulation of clay and other materials. 164. Which temperature regime indicates a mean annual temperature below 8°C and is typically found in colder regions? A. Hyperthermic B. Mesophilic C. Pergelic D. Thermic Answer: Pergelic (C) The Pergelic regime is specifically associated with cooler climates, with mean annual temperatures below 8°C. 165. Which of the following processes mainly results in the transformation of organic matter into ammonia in soil? A. Denitrification B. Ammonification C. Nitrification D. Symbiotic N-fixation Answer: Ammonification (B) Ammonification refers to the process where organic matter is converted into ammonia. 166. What is the main purpose of conducting a soil survey? A. To determine the impact of soil on agricultural outputs B. To analyze the geological features of a region C. To assess the chemical composition of soils D. To inventory soil resources and estimate productivity Answer: To inventory soil resources and estimate productivity (D) Soil surveys provide an inventory of soil resources, which helps in estimating productivity and understanding soil behavior. 167. Which order of soil survey is primarily focused on detailed studies for experiments? A. 2nd Order B. 1st Order C. 3rd Order D. 5th Order Answer: 1st Order (B) The 1st Order of soil survey is very intensive and detailed, specifically for experiments and building sites. 168. What is a primary characteristic used to differentiate soil orders in classification? A. Soil moisture levels B. Plant root penetration C. Soil color D. Major diagnostic horizon Answer: Major diagnostic horizon (D) The first level of soil classification is based on the major diagnostic horizon which helps identify different soil orders. 169. What does the 'great group' level of soil classification primarily organize according to? A. Vegetative cover B. Soil texture C. Chemical properties D. Arrangement of horizons Answer: Arrangement of horizons (D) The 'great group' classification divides soils based on the arrangement of soil horizons and their properties. 170. In soil taxonomy, which of the following is NOT a principal factor affecting soil genesis? A. Land use practices B. Soil property C. Climate effects D. Physical weathering Answer: Land use practices (A) Soil genesis is primarily influenced by inherent soil properties, climate, and physical processes such as weathering, while land use practices are not direct factors. 171. Which consideration is NOT included in land suitability classes? A. Wetness B. Soil texture C. Limitations to tillage D. Erosion/runoff potential Answer: Soil texture (B) While soil texture plays a role in determining soil characteristics, it is not directly listed among the considerations for land suitability classes. 172. What is the range of land area covered by the 4th order of soil survey? A. 0.6-4 hectares B. 252-4,000 hectares C. 1.6-16 hectares D. 16-252 hectares Answer: 16-252 hectares (D) The 4th order of soil survey is extensive and covers a range of 16 to 252 hectares, focusing on broad land use. 173. Which level of soil classification deals with the division according to uses in plant growth? A. Subgroup B. Order C. Series D. Family Answer: Family (D) The family level in soil classification is specifically divided based on their uses in supporting plant growth. 174. In soil classification, what is the significance of the 'suborder' level? A. It assesses soil fertility and nutrient levels. B. It determines the presence of organic matter. C. It indicates the structural arrangement of soil layers. D. It divides order according to moisture and temperature regimes. Answer: It divides order according to moisture and temperature regimes. (D) The suborder level divides the order into categories based on specific moisture and temperature regimes. 175. What is the basic unit of soil classification in the mentioned taxonomy? A. Great group B. Series C. Family D. Order Answer: Series (B) In the hierarchy of soil classification, the series is recognized as the basic unit contributing to the broader context of soil taxonomy. 176. Which method is effective in managing salinity in soils with high soluble salts? A. Apply organic matter B. Use ammonium sulfate C. Irrigation and regular drainage D. Deep plowing Answer: Irrigation and regular drainage (C) Irrigation and regular drainage help to remove salts, reducing salinity in affected soils. 177. What is a common practice for alleviating iron toxicity in paddy soils? A. Apply gypsum B. Spray foliar fertilizers C. Use rice hull ash D. Regular drainage Answer: Regular drainage (D) Regular drainage can help to oxidize iron and reduce toxicity levels in flooded conditions. 178. Which practice is recommended for improving soil texture and enhancing moisture retention? A. Deep plowing B. Employ drip irrigation C. Apply compost D. Use of tolerant rice varieties Answer: Apply compost (C) Applying compost improves soil texture and enhances moisture retention capabilities. 179. What is the primary function of micropores in soil? A. Storage of nutrients B. Retention of water C. Facilitating drainage D. Aeration of root systems Answer: Retention of water (B) Micropores are responsible for holding water, which is essential for plant growth. 180. Which statement best describes the effect of soil texture on bulk density? A. Silt has the highest bulk density B. Sand increases compaction C. Clay retains moisture better than sand D. Bulk density is not affected by texture Answer: Clay retains moisture better than sand (C) Clay particles can hold more moisture compared to sand, affecting bulk density. 181. Which nutrient management technique addresses zinc deficiency in crops? A. Apply foliar fertilizers containing zinc B. Use phosphate fertilizers C. Drain waterlogged soils D. Implement deep plowing Answer: Apply foliar fertilizers containing zinc (A) Foliar fertilizers containing zinc, such as ZnSO4, are effective in addressing zinc deficiency. 182. What is the relationship between organic matter decomposition and soil properties? A. Decomposition moderates pH and enhances nutrient availability B. Decomposition reduces nutrient availability C. Decomposition has no effect on soil structure D. Decomposition increases acid levels Answer: Decomposition moderates pH and enhances nutrient availability (A) Decomposition of organic matter moderates soil pH and improves nutrient availability for plants. 183. Which of the following is a characteristic of sodic soils? A. Excessive sodium content B. Low organic matter content C. High acidity levels D. High nitrogen availability Answer: Excessive sodium content (A) Sodic soils are characterized by excessive sodium content, affecting soil structure and fertility. 184. What is a key factor influencing soil genesis in tropical climates? A. Soil compaction B. Fertilizer application C. Temperature variations D. Rainfall patterns Answer: Rainfall patterns (D) Rainfall patterns significantly influence soil formation processes, especially in tropical regions. 185. Which approach can help in managing waterlogged conditions in lowland soils? A. Applying gypsum B. Using cover crops C. Constructing drainage canals D. Employing mulching Answer: Constructing drainage canals (C) Constructing canals to drain excess water is an effective method to manage waterlogged conditions. 186. What is the main factor affecting the accumulation of soil organic matter (SOM)? A. Organic carbon input B. Soil texture C. Temperature D. Microbial activity Answer: Microbial activity (D) Microbial activity enhances the decomposition and mineralization of organic materials, influencing SOM. 187. Which component of soil organic matter generally has the lowest percentage? A. Hemicellulose B. Water soluble fraction C. Cellulose D. Lignin Answer: Lignin (D) Lignin is usually present in a smaller proportion compared to cellulose and hemicellulose. 188. How does flooding most directly influence soil composition? A. By reducing ferric phosphate B. By decreasing microbial activity C. By increasing organic matter accumulation D. By enhancing microbial diversity Answer: By reducing ferric phosphate (A) Flooding reduces ferric phosphate availability, impacting nutrient uptake in plants. 189. What is the average carbon-to-nitrogen (C/N) ratio for finished compost? A. 30:1 B. 14:1 - 20:1 C. 25:1 - 30:1 D. 10:1 Answer: 14:1 - 20:1 (B) The typical C/N ratio of finished compost falls between 14:1 and 20:1, indicating balanced nutrient availability. 190. Which group of microbes is primarily involved in the reduction of sulfate to sulfide? A. Fusarium B. Desulfovibrii & Desulfotomaculum C. Bacillus D. Cytophaga Answer: Desulfovibrii & Desulfotomaculum (B) Desulfovibrii and Desulfotomaculum are specifically noted for their role in sulfate reduction. 191. What happens to organic matter when soil is cultivated? A. It remains unchanged. B. It declines due to enhanced oxidation. C. It becomes more nutrient-rich. D. It accumulates due to faster decomposition. Answer: It declines due to enhanced oxidation. (B) Cultivation leads to enhanced oxidation and microbial activity, resulting in a decline of organic matter. 192. What specific role do mycorrhizae play in soil health? A. Reduce iron precipitation B. Fix atmospheric nitrogen C. Decompose lignin D. Assist in phosphorus absorption Answer: Assist in phosphorus absorption (D) Mycorrhizae facilitate phosphorus absorption, which is crucial for plant growth. 193. Which type of mycorrhizae are known to penetrate plant root cells? A. Ectomycorrhiza B. Endomycorrhiza C. Both B and C D. Arbuscular mycorrhiza Answer: Both B and C (C) Both endomycorrhiza and arbuscular mycorrhiza penetrate root cells, enhancing nutrient exchange. 194. What property is primarily examined when assessing soil texture? A. Soil pH B. Soil bulk density C. Particle size distribution D. Organic matter content Answer: Particle size distribution (C) Soil texture is determined by particle size distribution, which influences various soil characteristics. 195. Which factor significantly affects the decomposition of cellulose in composting? A. Temperature B. Moisture levels C. Soil mineral content D. Microbial community composition Answer: Microbial community composition (D) The composition of microbial communities is crucial for the effective decomposition of cellulose and other organic materials. 196. What is the primary chemical process involved in the transformation of calcite into calcium carbonate under acidic conditions? A. Leaching B. Erosion C. Hydrolysis D. Carbonation Answer: Carbonation (D) Carbonation involves the reaction of carbonic acid with minerals, leading to the formation of carbonates. 197. Which factor primarily influences the rate of chemical weathering in soils? A. Temperature and moisture B. Soil texture C. Mineral composition D. Organic matter content Answer: Temperature and moisture (A) Temperature and moisture are critical factors that affect the rate at which chemical reactions occur in soils. 198. Which stage of soil formation primarily involves the addition of organic matter to the soil profile? A. Soil horizon formation B. Chemical weathering C. Physical weathering D. Organic matter addition Answer: Organic matter addition (D) Organic matter addition is a crucial stage in the development of healthy soils, enhancing fertility and structure. 199. In the context of soil components, which statement accurately describes the gas content of soil? A. Noble gases are significant components of soil gas composition. B. Oxygen is present in higher concentrations than nitrogen. C. Soil gas composition is primarily made up of carbon dioxide. D. Nitrogen comprises the least amount of gas in soil. Answer: Soil gas composition is primarily made up of carbon dioxide. (C) Carbon dioxide is released during organic matter decomposition, leading to its notable presence in soil gas. 200. Which term refers to the natural body that serves as a medium for plant growth? A. Pedon B. Soil horizon C. Soil profile D. Polypedon Answer: Pedon (A) A pedon is the smallest unit of soil that exhibits all soil characteristics and is critical in soil studies. 201. Which physical property of soil is characterized by the ability to resist deformation and compaction? A. Hydraulic conductivity B. Bulk density C. Plasticity D. Porosity Answer: Plasticity (C) Plasticity refers to the behavior of soil when subjected to stress, indicating its resistance to flow and compaction. 202. What role do living organisms play in the soil formation process? A. They cause bioturbation, mixing soil layers. B. They enhance nutrient leaching. C. They mainly contribute to soil erosion. D. They primarily decompose inorganic materials. Answer: They cause bioturbation, mixing soil layers. (A) Bioturbation signifies the mixing of soil layers by living organisms, significantly influencing soil structure and fertility. 203. Which of the following approaches in soil study focuses on the classification and description of soil types? A. Microbiology B. Survey & classification C. Fertility management D. Conservation & management Answer: Survey & classification (A) Survey & classification is essential for understanding soil characteristics and their implications for land use. 204. Which soil order is primarily designed for extensive land use and encompasses areas of 16 to 252 hectares? A. 2nd order B. 4th order C. 1st order D. 3rd order Answer: 4th order (B) The 4th order of soil survey is intended for broad land use and covers a significant area. 205. In soil classification, what is the term for the division that categorizes soil based on its major diagnostic horizon? A. Order B. Family C. Subgroup D. Great group Answer: Order (A) The first level of soil classification is the order, which is based on major diagnostic horizons. 206. Which of the following factors is considered in land suitability classes that affects soil management? A. Soil genesis B. Chemical composition C. Vegetative cover D. Moisture retention Answer: Moisture retention (D) Moisture retention is crucial in determining land suitability and soil management practices. 207. What does the 'series' level in soil taxonomy primarily denote? A. Basic unit of classification B. Type of soil amendment C. Erosion potential D. Moisture regime classification Answer: Basic unit of classification (A) The series level represents the basic unit of soil classification, with many types identified. 208. Which type of property is NOT readily observable and is also crucial for understanding soil genesis? A. Ecosystem interactions B. Soil strata C. Soil chemical reactions D. Physical texture Answer: Soil chemical reactions (C) Soil chemical reactions are important for understanding soil genesis but are not readily observable. 209. What aspect of soil fertility primarily influences plant growth according to its classification? A. Soil structure B. Water retention capacity C. Soil texture only D. Organic matter levels Answer: Organic matter levels (D) Organic matter levels are a critical factor affecting soil fertility and thus plant growth. 210. In the context of soil survey levels, which level involves a very intensive survey for detailed experimental purposes? A. 2nd order B. 1st order C. 5th order D. 3rd order Answer: 1st order (B) The 1st order of soil survey is designed for intensive, detailed studies, especially for experiments. 211. Which category in land suitability classes primarily addresses the potential for erosion and runoff? A. Tillage limitations B. Wetness conditions C. Erosion/runoff potential D. Rooting depth constraints Answer: Erosion/runoff potential (C) Erosion and runoff potential is a critical consideration in assessing land suitability classes. 212. Which level of classification divides soil into suborders based on moisture and temperature regimes? A. Order B. Suborder C. Family D. Great group Answer: Suborder (B) The suborder level categorizes soil further by its moisture and temperature regimes. 213. How does the term 'family' in soil taxonomy primarily categorize soil? A. According to plant growth uses B. By color characteristics C. By pH levels D. By soil organic content Answer: According to plant growth uses (A) The family level in soil taxonomy classifies soil types according to their suitability for different plant growth uses. 214. Which soil order is characterized by an accumulation of organic matter and a suitability for pasture when conserved? A. Mollisol B. Andisol C. Histosol D. Entisol Answer: Histosol (C) Histosols are rich in organic matter and are often found in wetland environments, making them suitable for conservation. 215. Which process relates to the conversion of nitrogen gas into ammonia in soil through non-symbiotic means? A. Denitrification B. Symbiotic N-fixation C. Ammonification D. Nitrification Answer: Ammonification (C) Ammonification involves the conversion of organic nitrogen into ammonia, a key step in the nitrogen cycle. 216. Which type of bacteria primarily facilitates the solubilization of calcium phosphate in the soil? A. Aspergillus B. Mycobacterium C. Pseudomonas D. Fusarium Answer: Pseudomonas (C) Pseudomonas species are known for their ability to solubilize calcium phosphate, making it more available for plant uptake. 217. What significantly affects the accumulation of soil organic matter in different ecosystems? A. Depth of soil horizons in grasslands B. Concentration of inorganic minerals C. Temperature variation in forest ecosystems D. Turnover rate of vegetative matter Answer: Turnover rate of vegetative matter (D) Grasslands accumulate more organic matter due to a faster turnover of vegetative matter compared to forests. 218. Which soil temperature regime is characterized by a mean annual temperature between 15°C and 22°C? A. Mesophilic B. Pergelic C. Thermic D. Hyperthermic Answer: Thermic (C) The thermic temperature regime is defined by specific temperature ranges that affect soil processes and fertility. 219. Which statement regarding the terms 'aerobic' and 'anaerobic' is accurate in the context of soil microorganisms? A. Anaerobic bacteria thrive in oxygen-rich environments. B. Aerobic organisms can function in the absence of oxygen. C. Anaerobic organisms require oxygen for survival. D. Aerobic bacteria require oxygen for their metabolic processes. Answer: Aerobic bacteria require oxygen for their metabolic processes. (D) Aerobic bacteria thrive in environments where oxygen is available and are essential for various soil processes. 220. Which component of soil organic matter has the highest range in percentage? A. Cellulose B. Hemicellulose C. Water soluble fraction D. Lignin Answer: Cellulose (A) Cellulose typically ranges from 15-60% in soil organic matter composition. 221. Which type of mycorrhizae is known for penetrating plant root cells? A. Endomycorrhizae B. Ectomycorrhizae C. Exomycorrhizae D. Arbuscular mycorrhizae Answer: Endomycorrhizae (A) Endomycorrhizae specifically penetrate cells, aiding in nutrient absorption. 222. How does microbial activity affect organic matter in cultivated soils? A. Increases organic matter accumulation B. Enhances the oxidation process C. Increases the C/N ratio D. Decreases microbial diversity Answer: Enhances the oxidation process (B) Cultivation leads to enhanced oxidation and microbial activity, reducing organic matter. 223. Which of the following fungal genera is most associated with cellulose decomposition? A. Trichoderma B. Fusarium C. Penicillium D. Aspergillus Answer: Aspergillus (D) Aspergillus is one of the fungal genera that plays a significant role in cellulose decomposition. 224. What is the primary product of the thermophilic stage in composting? A. High carbon content B. Nutrient-rich liquid C. Acidic organic compounds D. Humus-like organic material Answer: Humus-like organic material (D) The thermophilic stage in composting leads to the creation of humus-like organic materials. 225. Which process is primarily driven by the activity of Iron bacteria in soils? A. Oxidation of lignin B. Reduction of sulfate to sulfide C. Ferrous oxidation D. Decomposition of organic matter Answer: Ferrous oxidation (C) Iron bacteria primarily facilitate the ferrous oxidation from Fe2+ to Fe3+. 226. What is the carbon-to-nitrogen (C/N) ratio range of finished compost? A. 10:1 - 15:1 B. 8:1 - 12:1 C. 14:1 - 20:1 D. 20:1 - 30:1 Answer: 14:1 - 20:1 (C) The typical C/N ratio of finished compost is between 14:1 and 20:1. 227. Which of the following chemical forms of sulfur is involved in microbial transformation processes? A. Organic sulfur compounds B. Elemental sulfur C. Thiosulfate D. All of the above Answer: All of the above (D) Microbial processes can involve the transformation of organic sulfur, elemental sulfur, and thiosulfate. 228. What role do Actinomycetes play in soil health? A. Increase soil acidity levels B. Enhance water retention in soil C. Simplify organic compounds D. Compete with fungi for nutrients Answer: Simplify organic compounds (C) Actinomycetes attack and simplify organic compounds, serving as a link between bacteria and fungi. 229. What practice can help mitigate iron toxicity in flooded soils? A. Dig holes for better drainage B. Spray plants with oil-based fertilizers C. Apply ammonium sulfate to increase nitrogen levels D. Regularly drain the soil to manage water levels Answer: Regularly drain the soil to manage water levels (D) Regular drainage is crucial to control iron levels in flooded conditions. 230. Which soil texture is described as smooth and powdery? A. Clay B. Sand C. Silt D. Gravel Answer: Silt (C) Silt has a fine texture that feels smooth and powdery when manipulated. 231. What is a common consequence of excessive soluble sodium in soils? A. Decrease in soil organic matter B. Toxic accumulation of soluble salts C. Increase in microbial activity D. Improved nutrient absorption for plants Answer: Toxic accumulation of soluble salts (B) Soils with excessive sodium content often develop high levels of soluble salts, leading to toxicity. 232. Which approach is NOT advised for managing calcareous soil conditions? A. Regular mulching with nitrogen-rich materials B. Applying gypsum to improve drainage C. Incorporating organic matter into the soil D. Using acidifying fertilizers Answer: Regular mulching with nitrogen-rich materials (A) Mulching with nitrogen-rich materials is generally not advised as it may not address the specific needs of calcareous soils. 233. Which property is most affected by the bulk density of soil? A. Soil texture classification B. Soil color variation C. Nutrient retention capacity D. Water infiltration rate Answer: Water infiltration rate (D) Bulk density is directly related to the water infiltration rate in soils. 234. What aspect is essential for the amendment of sodic soils? A. Utilize gypsum to reclaim sodium. B. Incorporate more sand to improve drainage. C. Regularly apply phosphorus. D. Increase organic matter through compost. Answer: Utilize gypsum to reclaim sodium. (A) Gypsum is commonly used to replace sodium in sodic soils, improving their overall structure and fertility. 235. Which method is effective in managing waterlogged soils? A. Increasing crop density B. Underfilling with silt C. Constructing canals for drainage D. Using salt-resistant plant varieties Answer: Constructing canals for drainage (C) Constructing drainage canals is a direct approach to managing excess water in waterlogged soils. 236. Which component of soil typically provides the most available micronutrients? A. Clay minerals B. Sand particles C. Silt content D. Organic matter Answer: Organic matter (D) Organic matter significantly enhances the availability of micronutrients for plant uptake. 237. What characteristic of acid sulfate soil impacts its management? A. Rich biodiversity B. High organic matter content C. Low pH affecting nutrient solubility D. Extensive macropore space Answer: Low pH affecting nutrient solubility (C) The low pH of acid sulfate soils can limit nutrient availability, complicating management practices. 238. Which of the following is critical for increasing phosphorus availability in soils? A. Use of mycorrhizal fungi B. Frequent irrigation with distilled water C. Planting fast-growing species D. Application of calcium carbonate Answer: Use of mycorrhizal fungi (A) Mycorrhizal fungi play a significant role in enhancing the availability of fixed phosphorus in the soil. 239. What is the role of temperature in the chemical reactions associated with soil formation? A. Higher temperatures increase reaction rates according to the rate equation. B. Temperature leads to increased physical weathering, not chemical. C. Higher temperatures promote slower reactions. D. Temperature does not influence soil chemical reactions. Answer: Higher temperatures increase reaction rates according to the rate equation. (A) Higher temperatures accelerate the chemical reactions involved in soil formation. 240. Which of the following factors is least associated with bioturbation in soil formation? A. Heavy rainfall causing erosion. B. Earthworms mixing soil layers. C. Root growth penetrating soil. D. Microbial activity breaking down organic matter. Answer: Heavy rainfall causing erosion. (A) Bioturbation primarily involves organisms mixing the soil, rather than rainfall- related erosion. 241. Which process involves the dissolution of silica in soil chemistry? A. Carbonation B. Solution C. Hydrolysis D. Oxidation Answer: Solution (B) Dissolution of silica in the presence of H2CO3 is categorized under the solution process. 242. What is the typical bulk density range for clay soils? A. 1.20 – 1.80 g/cm3 B. 1.13 g/cm3 C. 1.80 – 2.00 g/cm3 D. 2.70 g/cm3 Answer: 1.13 g/cm3 (B) Clay soils generally exhibit a lower bulk density of around 1.13 g/cm3. 243. In the context of soil classification, what is the meaning of 'polypedon'? A. A single layer of soil. B. Multiple hexagonal pedons. C. The basic unit of soil. D. A soil horizon with distinct properties. Answer: Multiple hexagonal pedons. (B) A polypedon encompasses multiple pedons within a certain area. 244. Which mechanism primarily facilitates the movement of water in the process of soil formation? A. Relief/topography B. Organic matter addition C. Chemical weathering processes D. Wind erosion Answer: Relief/topography (A) Relief or topography is crucial for determining water movement in soil formation. 245. Which approach in soil study primarily focuses on understanding the elemental composition and reactions of soil? A. Fertility B. Physics C. Chemistry D. Microbiology Answer: Chemistry (C) Soil Chemistry involves the study of elemental composition and reactions occurring in soils. 246. Which stage of soil formation is directly influenced by the addition of organic matter? A. Chemical weathering B. Particle rearrangement C. Soil horizon formation D. Physical weathering Answer: Soil horizon formation (C) The addition of organic matter is essential for fostering the development of distinct soil horizons. 247. Which soil order is characterized by a significant accumulation of organic matter and a high likelihood of being waterlogged? A. Entisol B. Andisol C. Histosol D. Mollisol Answer: Histosol (C) Histosols are known for their high organic matter content and are commonly found in waterlogged conditions. 248. What is the primary role of aerobic bacteria in soil nitrogen cycles? A. To fix nitrogen from the atmosphere B. To convert nitrates into nitrogen gas C. To convert organic nitrogen into ammonium D. To immobilize inorganic nitrogen Answer: To convert organic nitrogen into ammonium (C) Aerobic bacteria primarily facilitate the process of ammonification, converting organic nitrogen into ammonium. 249. Which process is responsible for the conversion of soil organic matter into ammonia? A. Ammonification B. N2 Fixation C. Nitrification D. Denitrification Answer: Ammonification (A) Ammonification is the process where organic matter is broken down to produce ammonia, primarily carried out by various bacteria. 250. Which layer of soil is typically described as having a high percentage of illuvial accumulations of aluminum and iron? A. Ochric Horizon B. Sombic Horizon C. Argilic Horizon D. Mollic Horizon Answer: Argilic Horizon (C) The Argilic Horizon is specifically characterized by an accumulation of clay, aluminum, and iron. 251. What aspect of soil determines its suitability for agricultural use, particularly in terms of moisture retention and nutrient availability? A. Soil pH B. Soil color C. Soil texture D. Soil depth Answer: Soil texture (C) Soil texture significantly influences moisture retention and nutrient availability, affecting its overall suitability for agriculture. 252. Which factor primarily contributes to the accumulation of soil organic matter in grasslands compared to forested areas? A. Lower soil moisture levels B. Faster turnover of vegetative matter C. Higher microbial activity in wetter conditions D. Longer lifespan of vegetative matter Answer: Faster turnover of vegetative matter (B) Grasslands tend to have a faster turnover of vegetative matter which promotes higher accumulation of organic matter. 253. Which microbial process plays a key role in the reduction of sulfate to sulfide in soil chemistry? A. Desulfovibrio activity B. Decomposition of lignin C. Fermentation of cellulose D. Oxidation of organic matter Answer: Desulfovibrio activity (A) Desulfovibrio are known to reduce sulfate to sulfide, a crucial process in microbial sulfur transformation. 254. What is the typical C/N ratio range for finished compost products? A. 10:1 to 15:1 B. 5:1 to 10:1 C. 14:1 to 20:1 D. 20:1 to 25:1 Answer: 14:1 to 20:1 (C) The C/N ratio for finished compost usually falls within 14:1 to 20:1, indicating a balanced composition. 255. Which property of soil organic matter is influenced by moisture levels? A. Plant nutrient availability B. Decomposition speed C. Chemical composition D. Accumulation rate Answer: Accumulation rate (D) Soil organic matter accumulation is directly proportional to moisture; more moisture generally leads to more organic matter. 256. Which type of mycorrhizae is characterized by its ability to penetrate plant root cells? A. Arbuscular mycorrhiza B. Endomycorrhiza C. Ectomycorrhiza D. Ericoid mycorrhiza Answer: Endomycorrhiza (B) Endomycorrhizae have the unique ability to penetrate root cells, aiding in nutrient absorption. 257. Which chemical property of soils is indicated by the cmol value of calcium? A. Calcium ion concentration B. Presence of organic carbon C. Organic matter retention D. Soil permeability Answer: Calcium ion concentration (A) The cmol value represents the concentration of calcium ions in soil, an important indicator of soil chemistry. 258. What effect does flooding generally have on ferric phosphate levels in soil? A. Reduces ferric phosphate levels B. Stabilizes ferric phosphate content C. Increases availability of ferric phosphate D. Promotes oxidation of ferric phosphate Answer: Reduces ferric phosphate levels (A) Flooding tends to reduce ferric phosphate levels among other impacts on soil chemistry. 259. What role do actinomycetes primarily play in soil ecology? A. Enhancing water retention in soil B. Decomposing heavy metals C. Breaking down complex organic compounds D. Fixing nitrogen from the atmosphere Answer: Breaking down complex organic compounds (C) Actinomycetes are known for their ability to attack and simplify organic compounds, acting as an intermediary between bacteria and fungi. 260. Which of the following fungi is specifically noted for its role in cellulose decomposition? A. Bacillus B. Trichoderma C. Fusarium D. Aspergillus Answer: Trichoderma (B) Trichoderma is recognized for its effective role in the decomposition of cellulose within composting processes. 261. What is the primary purpose of composting in soil management? A. Create humus-like organic materials B. Accelerate soil erosion C. Enhance soil salinity D. Increase organic pollution levels Answer: Create humus-like organic materials (A) Composting is crucial for creating humus-like organic materials that improve soil structure and fertility. 262. Which order of soil survey is primarily designed for experimental purposes? A. 3rd order B. 5th order C. 1st order D. 2nd order Answer: 1st order (C) The 1st order of soil survey is very intensive and detailed, suitable for experiments and building sites. 263. What is the primary criterion for differentiating soil suborders? A. Particle size distribution B. Presence of organic matter C. Color variations D. Moisture and temperature regimes Answer: Moisture and temperature regimes (D) Suborders are divided based on the moisture and temperature regimes influencing soil characteristics. 264. In soil taxonomy, which level directly correlates with the arrangement of soil particles? A. Great group B. Family C. Suborder D. Order Answer: Great group (A) The great group classification focuses on the arrangement of primary soil properties. 265. Which of the following best describes land suitability considerations related to erosion? A. Potential for surface runoff B. Soil nutrient availability C. Soil moisture retention capacity D. Soil pH levels Answer: Potential for surface runoff (A) Erosion considerations include the potential for surface runoff affecting land usability. 266. What type of soil survey would best support extensive community planning? A. 3rd order B. 2nd order C. 1st order D. 4th order Answer: 3rd order (A) The 3rd order of soil survey is designed for extensive community use and covers larger areas. 267. What is the primary focus of soil property when classifying soil types? A. Water retention B. Soil texture only C. Major diagnostic horizon D. Color and structure Answer: Major diagnostic horizon (C) Soil classification begins with the major diagnostic horizon that distinguishes different soil orders. 268. In the context of soil fertility, what property most directly affects plant growth? A. Soil compaction B. Soil color C. Soil texture D. Soil depth Answer: Soil texture (C) Soil texture is critical as it influences water retention, aeration, and nutrient availability for plants. 269. Which aspect of soil genesis refers to factors that affect soil formation? A. Compressive strength B. Soil compaction C. Differences in soil taxa D. Readily observable property Answer: Readily observable property (D) Readily observable properties play a significant role in understanding factors that influence soil genesis. 270. What is the primary component that defines a soil 'series' in soil classification? A. Erosion resistance B. Organic matter content C. Basic unit of classification D. Soil structure type Answer: Basic unit of classification (C) A soil series is considered the basic unit of classification within the hierarchy of soil taxonomy. 271. Which limitation is considered when assessing land suitability for tillage? A. Soil temperature variations B. Soil moisture levels C. Depth of organic horizon D. Physical barriers to rooting Answer: Physical barriers to rooting (D) Limitations to tillage often relate to physical barriers that impede plant rooting and growth. 272. Which practice is most effective in reducing iron toxicity in soil? A. Add calcium carbonate to raise soil pH B. Apply organic fertilizer to enhance soil microbial activity C. Use phosphatic fertilizers to bind excess iron D. Implement regular drainage during flooding conditions Answer: Implement regular drainage during flooding conditions (D) Regular drainage helps to reduce the iron toxicity problem by managing excess iron in flooded conditions. 273. What is the primary function of micropores in soil? A. To hold water available to plants B. To allow for drainage of excess water C. To provide oxygen for root respiration D. To enhance soil structure and compaction Answer: To hold water available to plants (A) Micropores are specifically designed to hold water, making it available for plant use. 274. Which factor is least likely to affect soil bulk density? A. Soil texture and composition B. Organic matter content and management practices C. Soil moisture content at the time of sampling D. Topsoil thickness and color variations Answer: Topsoil thickness and color variations (D) While topsoil thickness can influence some properties, color variations do not directly impact soil bulk density. 275. What is the primary consequence of applying gypsum (CaSO4) to sodic soils? A. Reduces the soil pH significantly B. Promotes acidification to improve nutrient availability C. Increases the sodium content in soil D. Improves soil structure by replacing sodium with calcium Answer: Improves soil structure by replacing sodium with calcium (D) Gypsum improves soil structure by replacing sodium ions with calcium, which enhances soil drainage and reduces sodicity. 276. Which soil condition is primarily aggravated by high salinity content? A. Increased nutrient uptake efficiency by plants B. Decreased water availability for crops C. Enhanced microbial activity clogs pores D. Improved drainage characteristics of soil Answer: Decreased water availability for crops (B) High salinity can lead to osmotic stress in plants, decreasing their water uptake and overall availability. 277. In which scenario would employing mulching be most beneficial? A. In conditions of high salinity and poor drainage B. To prevent soil erosion and conserve moisture C. When soil is excessively saturated leading to waterlogging D. In highly acidic soils affecting crop growth Answer: To prevent soil erosion and conserve moisture (B) Mulching helps to prevent erosion and conserve soil moisture by protecting the surface layer from direct rainfall impact. 278. Which property of soil is critically influenced by its texture? A. Soil organic matter decomposition rates B. Soil microbiome diversity C. Soil aeration and drainage capacity D. Soil color variations under different moisture conditions Answer: Soil aeration and drainage capacity (C) Soil texture directly affects aeration and drainage, as it determines the size and arrangement of soil particles. 279. What can contribute significantly to the low levels of zinc availability in certain soils? A. Excessive potassium application B. High iron content leading to competitive uptake C. Soil with high organic matter content D. High pH levels resulting in precipitation of zinc Answer: High iron content leading to competitive uptake (B) High levels of iron can hinder the absorption of zinc, leading to deficiency in plants that require this micronutrient. 280. Which treatment method is best used to improve phosphorus availability in soils? A. Frequent cultivation to enhance aeration B. Deep plowing with organic amendments C. Use of nitrogen-rich fertilizers to stimulate growth D. Application of compost enriched with mycorrhizae Answer: Application of compost enriched with mycorrhizae (D) Mycorrhizae are known to enhance the availability of fixed phosphorus to plants, making this an effective treatment. 281. What defines the condition of acid sulfate soils? A. High nutrient retention and moisture content B. Rich organic matter accumulation in flooded areas C. Low pH often near 4.0 due to sulfur oxidation D. Increased salinity from saltwater intrusion Answer: Low pH often near 4.0 due to sulfur oxidation (C) Acid sulfate soils are characterized by their low pH caused by the oxidation of sulfur present in submerged soils. 282. Which soil type is typically associated with high organic matter suitability for pasture when conserved? A. Andisol B. Histosol C. Mollisol D. Entisol Answer: Histosol (B) Histosol is characterized by high organic matter content, making it suitable for pasture use when conserved. 283. Which process describes the conversion of organic nitrogen back to inorganic forms in soil? A. Nitrification B. Solubilization C. Ammonification D. Denitrification Answer: Denitrification (D) Denitrification is the process where nitrates are converted back into nitrogen gas, closing the nitrogen cycle. 284. Which horizon is characterized by significant accumulation of aluminum and iron oxides? A. Argilic horizon B. Plaggen horizon C. Mollic horizon D. Oxic horizon Answer: Argilic horizon (A) The Argilic horizon is known for its illuvial accumulation of clay, aluminum, and iron oxides. 285. What type of bacteria is primarily responsible for the solubilization of calcium phosphate in soil? A. Mycobacterium B. Pseudomonas C. Penicillium D. Bacillus Answer: Pseudomonas (B) Pseudomonas is a key genus of bacteria that helps in solubilizing calcium phosphate, enhancing nutrient availability in soil. 286. Which soil classification describes a soil with a mean annual temperature that is categorized as hyperthermic? A. Histosol B. Montmorillonite C. Mollisol D. Gellisol Answer: Mollisol (C) Mollisols are characterized by their fertility and typically have a hyperthermic temperature regime of more than 22°C. 287. What process involves the reaction of carbonic acid with calcite to form calcium carbonate? A. Hydrolysis B. Leaching C. Oxidation D. Carbonation Answer: Carbonation (D) Carbonation is a process where carbonic acid reacts with certain minerals, leading to the formation of bicarbonates or carbonates. 288. Which type of soil parent material is characterized by having no movement? A. Transported B. Colluvium C. Alluvium D. Sedentary Answer: Sedentary (D) Sedentary parent materials form in place and do not experience movement, distinguishing them from transported materials. 289. Which factor does NOT influence the chemical weathering of soils? A. Rainfall B. Soil texture C. Organic matter D. Temperature Answer: Soil texture (B) While soil texture affects physical properties, it is the climate factors like temperature and rainfall that primarily drive chemical weathering. 290. In soil physics, what term is used to describe the process that leads to soil mixing by living organisms? A. Bioturbation B. Rearrangement C. Erosion D. Hydrolysis Answer: Bioturbation (A) Bioturbation refers to the disturbance and mixing of soil caused by organisms such as earthworms and insects. 291. What does the term 'pedon' refer to in soil classification? A. A large area of soil B. The basic unit of soil C. Multiple soil types D. A single layer of soil Answer: The basic unit of soil (B) A pedon is defined as the smallest three-dimensional unit of soil that contains all its vertical properties. 292. Which stage in soil formation is primarily characterized by the addition of organic material? A. Physical weathering B. Soil horizon formation C. Organic matter addition D. Particle rearrangement Answer: Organic matter addition (C) Organic matter addition is a specific stage in soil formation that enhances soil fertility and structure. 293. Which mineral is associated with characteristics of heavy minerals in soil? A. Hematite B. Calcite C. Quartz D. Gypsum Answer: Hematite (A) Hematite is an iron-rich mineral commonly classified as a heavy mineral due to its density. 294. What represents the transition layer between two soil horizons? A. R horizon B. AB layer C. C horizon D. A horizon Answer: AB layer (B) The AB layer is known as the transition layer, bridging the two different soil horizons. 295. 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? A. 4th order B. 1st order C. 2nd order D. 3rd order Answer: