lecture notes crop sci.pdf

CRPSC 10 LECTURE NOTES Principles of Soil Science MODULE I Topic: Introduction to Soil Science Learning Objectives: At the end of this module...

CRPSC 10 LECTURE NOTES Principles of Soil Science MODULE I Topic: Introduction to Soil Science Learning Objectives: At the end of this module, you are expected to: 1. define soil science and what is a soil and understand the various scientific approaches used by scientist aligned to soil science. 2. identify the components of soil and their significance in plant growth, as well as analyze the percentage of each component occupies within the total volume Philippine Soils Finite resources 30 Million hectares Growing population – lands (prime agricultural lands) will have to be sequestered for housing, industrial sites, schools, parks, markets, etc. increasing population leads to prime agricultural land being repurposed for housing, industrial, etc. The Historical Transition Earliest traces- Fertile Crescent Consequence of Agricultural Revolution Increase population Shifting cultivation Kaingin System Soil is important: Innovations in sustainable agriculture Soil health management and ecological restoration Agricultural productivity which contributes to food security Preserving soil biodiversity through soil health management Climate change mitigation Soil Science defined: deals with the study of soils as a natural resource on the surface of the earth, encompassing: 1. soil formation 2. classification and mapping 3. physical, chemical, biological and fertility properties of soil per se and those properties in relation to the management for crop production. AREAS IN SOIL SCIENCE Soil Fertility o studies soil’s inherent capacity to supply nutrient elements and their availability, evaluation of the soil fertility status, and explores use of fertilizer and soil amendments o focuses on the availability and forms of essential elements for plant growth Soil Microbiology o examines the major microbial groups, their ecology, and biochemical activities concerning soil fertility o studies microbial communities in the soil, their roles in soil fertility, land reclamation, and the relationship between soil microbes and plant nutrition or diseases. Soil Chemistry o Deals with the study of nature and composition of soils, physico-chemical properties and reactions within soils including ionic equilibria, and submerged soils., o Deals with chemical constitution, chemical properties and processes taking place in the soil o Characterization of the reactions of the nutrients in the soil and in the soil solution Soil Physics o Focuses on the physical properties of soils in relation to plant growth, including their measurement and analysis o Explores the mechanical behavior of soils and the physical forces influencing soil properties o Deals with the mechanical behavior of the soil mass (physical properties of soil with emphasis on the state and transport of matter (water and energy) o Deals with the characteristics, properties or reactions of a soil which are caused by physical forces, and which can be described by equations Soil Classification and Survey o Involves the study of soil formation, horizon differentiation, natural and comprehensive system of classification, mapping and soil survey reports. o Deals with the systematic rearrangement of soils into groups or categories based on their characteristics Soil Geology o Deals with the study of the common soil forming rocks and minerals, geologic processes, agencies and landforms in relation to agriculture Soil Conservation and Management o Addresses soil deterioration and its control, maintenance and improvement of soil fertility and productivity o Focuses on protecting of the soil against physical loss by erosion or chemical deterioration (combination of all management and land use method that safeguard the soil against deterioration by natural or human induced factors) o Totality of all tillage operations, cropping practices, fertilization, liming, etc. Land Use o Deals with the utilization or allocation of lands for general or broad purposes such as agriculture, settlement and military reservation Soil defined o the nature of soil affects the growth of plants, the storage of water, the composition of the soil atmosphere and the supply of plant nutrients. o A thin portion of earth crust which is a mixture of organic and inorganic materials formed from the weathering of rocks and minerals and whose properties are conditioned in various degrees by influence of climate, living organisms (plants and animals) and relief acting on the parent material over a period of time. It serves as a medium for plant growth. o “ the unconsolidated mineral material on the immediate surface of the earth that serves as a natural medium for the growth of land plants APPROACHES TO THE STUDY OF SOIL SCIENCE (Two views of Soil Science) o PEDOLOGICAL APPROACH (sees the soil as a distinct entity) o the soil is considered as a natural body with major emphasis on properties related to its genesis and classification as it occurs in the environment o The origin of the soil, its classification and its description are examined in Pedology. (From Greek word pedon, means soil or earth). Pedology o the study of soil as a natural body and does not focus on the soil’s immediate practical use. A pedologist studies, examines and classifies soil as they occur in their natural environment. o Pedology studies the factors and processes of soil formation and describes soil profiles, pedons, and surface patterns. o The word “pedology” has been used as a synonym for soil science and as another name for soil genesis, the study of changes in soil bodies. o Pedology, therefore, deals with the soil as “a natural entity to be studied as a thing complete in itself” (Cline, 1961). EDAPHOLOGICAL APPROACH (in relation to plant growth) Edophology (from Greek word edaphos, means soil or ground) is the study of soil from the standpoint of higher plants. Edaphologists consider the various properties of soil in relation to plant production. considers the physical, chemical and biological properties of the soil as they relate to crop production. The information gathered by the edaphologists would be of interest to farmers, agriculturists and foresters They are practical and have the production of food and fiber as their goal. They must determine the reasons for variation in the productivity of soils and find means for improvement. Edaphology science that deals with the influence of soils on living things, particularly plants, including man’s use of land for plant growth.  The subdisciplines of soil science such as soil fertility and soil conservation deal with the study of the soil Importance of Soil o Support growth of higher plants/medium for plant growth o plants depend on the soils for water and nutrient elements o provides an environment in which roots can function o as a system of water purification o Nature’s recycling system medium for waste disposal and nutrient cycling o habitat of soil microorganisms o engineering medium o The Earth’s crust – portion of the earth down to a depth of 16 kilometers, main source of material from which inorganic fraction of the soil is derived known as the parent material. o Dominated by two systems of compound o Silicate and oxide system o In addition, carbon system carbonates and organic compounds o 92 elements are known present in the earth’s crust MAJOR COMPONENTS OF SOIL Composition of soil on volume basis o The relative proportions of the four major components – mineral matter, organic matter, water and air – may vary widely, but generally lie within the ranges indicated mineral matter water, mineral 25% Org. matter matter, 45% air air 25% Org. matter, water 5% Figure 1. Ideal distribution of the four major components of soil The Solid Phase o Comprises about one-half or 50% of the total soil volume o Consists of inorganic and organic materials  mineral matter Org. matter air water water, 25% mineral matter, 45% Org. air 25% matter, 5% MINERAL MATTER o Makes up 45% of the soil, consisting of small rock fragments and minerals of various kinds. o Rock fragments are remnants of massive rocks from which the soil have been formed by weathering. o Consists of various sized particles derived from the breakdown of rocks and minerals and are classified as: o Sand – large-sized particles o Silt – medium-sized particles o Clay – small-sized particles ORGANIC MATTER o Constitutes about 5% of the total soil volume consisting of partially decayed and synthesized plant and animal residue, with humus as the most resistant decomposition product o It is usually black in color and it is colloidal in nature. o The surface soil is higher in OM because it is where deposition occurs. FUNCTIONS OF SOIL ORGANIC MATTER o Influences soil properties and plant growth o Promotes granulation of minerals largely responsible for loose and easy manageable condition of productive soils o Major source of N, P, S o Increases water holding capacity and soil aeration o Main source of energy for both plants and animal organisms o Increases nutrient holding capacity of the soil The Liquid Phase o Soil water contains dissolved organic and inorganic solutes and is called the soil solution. o Fills up the pore space and acts as universal solvent, nutrient carrier and nutrient in itself. o It also stabilizes soil temperature o Is totally dependent on the moisture content o Soil water also serves as a solvent in which soluble salts are dissolved.  o Contains varying amounts of water depending on factors such as precipitation, irrigation, and drainage. Water is essential for plant growth, microbial activity, and transport of nutrients within the soil Differences in the content of soil and atmospheric air ELEMENT Soil Air Atmospheric Air N2 78.60% 78.03% O2 20.00% 21.00% CO2 0.50% 0.03% Argon 0.9% 0.94% Traces of hydrogen, ammonia and oxides of sulfur and of nitrogen may be present (if close to industrial sites) Gaseous Phase o soil air consists primarily of N2 and oxygen (O2), it usually contains higher concentrations of carbon dioxide (CO2) than the atmosphere, and traces of other gases that are by-products of microbial metabolism. o Located in the mares of the soil pores separated by soil solids not occupied by water. o Has higher moisture content than the atmospheric air o The CO2 content of soil air is higher and more concentrated than 0.03% found in the atmosphere o Pore spaces between soil particles are filled with air, which is vital for soil respiration, oxygen exchange, and the growth of aerobic organisms ▪ Mineral soil- soil that contains less than 20% organic carbon ▪ Organic soil- soil that contains at least 20% organic carbon “Soil is the great connector of lives, the source and destination of all. It is the healer and restorer and resurrector, by which disease passes into health, age into youth, death into life.” - Wendell Berry- Prepared by: Precious Dane P. Tagas, MSc Faculty, Agricultural Science Department Licensed Agriculturist, 0017054