Soil Study

Organic Matter Soil organic matter is composed of decomposing residues (plants and animals), by-product formed by decomposition, microorganisms and materials resistant to further decomposition. Generally, a mineral soil contains 2-5 %organic matter. Organic matter plays a variety of roles in nutrient, water and biological cycles in soil system. Source of organic matter: common organic waste materials which could be used to increase soil organic matter include animal manures, crop residues, composts, green manure, sewage sludge, food processing wastes, industrial organic wastes, wood manufacturing wastes and municipal wastes. Factor Affecting Organic Matter in Soil The amount of organic matter in soil is the result of two processes: the addition of organic matter and the loss of organic matter through decomposition. The following four factors affect both addition and losses. Management                 Practices that increase plant growth on a field (cover crops, irrigation,

Importance of Soil pH pH is the negative log of the hydrogen ion activity of a soil.                                                                  pH  = -log (H + ) Here H +  represents the hydrogen ion activity in mol L -1 . The pH scale is the logarithm to the base 10 o the reciprocal o the hydrogen ion activity. As the pH of a solution goes from 7 to 6, the hydrogen concentration increases 10 times and OH ions decrease by 10 times. The pH scale extends from 1 to 14. Soils with pH less than 7 are acidic and those with a pH above 7 are alkaline or basic.   It is major factor in determining which trees, shrubs or grasses will dominate the land under natural conditions. pH influences the process involved in the formation and development of soils. Most minerals are soluble in acid soils than in alkaline soils thus releasing ions toxic to plants e.g. Al. It affects the availability of nutrients to the plants. Alkaline pH reduces the solubility of all the micronutrients

Basic Process of Soil Genesis During soil formation, the unconsolidated weathered material under goes many changes. These changes are brought about by variations in the four basic soil forming processes. Time required for a soil to develop the distinct layers (horizons). Horizons tend to develop more rapidly under warm, humid and forested conditions where there is enough water to move clay, humus and other colloids downward. Under ideal conditions recognisable soil profile may develop within 200 years and under less favourable conditions the time may extend to several thousand years. These four basic processes often referred as soil forming or pedogenic processes. They are responsible of soil genesis under all kind of environments. Addition                 Inputs of materials to the developing soil profile from outside sources are considered additions. For example, fallen plant leaves, dust, twigs, animal dung, salts or silica dissolved in groundwater and deposited near or at th

Role of Living Organisms in Soil Formation Soil formation means both the production of parent material and soil profile development. The process of weathering and soil profile development occurs simultaneously. The formation of soil happens over a very long period of time. It may take thousands of years. Soil is formed as results of weathering of rocks and minerals. The surface rocks break down into smaller pieces through a process of weathering and is then mixed with organic matter. Over time this creates a thin layer of soil and then lower plants grow and soil development is enhanced. Later on higher plants grow and attract animals. When the plants and animals die their bodies decay/decompose. Decaying matter makes the soil thick and rich. This continues until soil is fully developed. The activities of living plants, animals and the decomposition of their wastes and residues have marked influence on soil development. Soil organisms play a major role in soil profile differentia

Soil Morphology Soil morphology is the visual observation of morphological features of soil i.e. soil colour, texture and structure of horizon and arrangements of these horizons in the soil profile. This can be studied in the field by the naked eye (macro morphology), with the aid of hand lens and binocular stereoscope (meso morphology), with the electron microscope (micro morphology). Soil Profile                                 A vertical section of the soil showing different layers and extending into the C-horizon or parent material (R layer) is called soil profile. Horizon                                 It is a layer of soil approximately parallel to the soil surface, having different properties and characteristics from adjacent layers below or above it. Description of typical Soil Profile                                 A common sequence of horizons within a profile comprises of five master soil horizons i.e. O, A, E, B and C. Distinctions within these