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Mee Rr en ween ne ee pe ee ey cee tee pre ee teataen een ae uae, , Soil Air, , Continuation of atmospheric air (air present in soil), , Soil aeration:, , Constant exchange of gases from soil to atmosphere or vice versa, results in renewal of component of gases of soil air is called as soil aeration., Composition of atmospheric air & soil air:, , , , , , , , , , , , , , , , , , , , , , , , Soil air Atmospheric air, N(%) 79.2 79.9, O(%) 20.60 20.97, Co2(%) 0.3 0.03, Movement of soil air:, i Mass flow, Z, Diffusion, , Mass flow- When water is added to field either through irrigation or, precipitation which replaces soil air in large mass is called as mass flow., , Diffusion- Movement or solute or gases from higher concentration to lower, concentration., , Different gases have different partial pressure depending upon partial, pressures of gas movement of gas takes place from soil to atmosphere or, vice versa., , Example- co» in soil air has very high partial pressure that co. in, atmosphere thus co2 moves from soil air to atmosphere., , Factors affecting soil aeration :, , 1. Soil Texture, , 2. Soil Structure, , 3. Addition of organic matter, , 4. Soil moisture is inversally proportional to soil aeration., , Prepared by: Prof. S. B. Aware 43, , , , Scanned with CamScanner
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K. K. WAGH COLLEGE OF AGRICULTURE, NASHIK, , Importance of soil aeration :, , 1. It influences plant growth ., , 2. It is required for microbial activity ., , 3. Under anaerobic condition toxic substances/gases , for example, methane,, hydrogen sulphide are produced, , 4. Due to improper aeration it causes fruit diseases., , 5. Nutrient absorption is also affected due to low quantity of oxygen present, in the soil., , Factors Affecting the Composition of Soil Air:, , 1. Nature and condition of soil: The quantity of oxygen in soil air is less, than that in atmospheric air. The amount of oxygen also depends upon the, soil depth. The oxygen content of the air in lower layer is usually less than, that of the surface soil. This is possibly due to more readily diffusion of the, oxygen from the atmosphere into the surface soil than in the subsoil. Light, texture soil or sandy soil contains much higher percentage than heavy soil., The concentration of CO2 is usually greater in subsoil probably due to more, sluggish aeration in lower layer than in the surface soil., , 2. Type of crop: Plant roots require oxygen, which they take from the soil, air and deplete the concentration of oxygen in the soil air. Soils on which, crops are grown contain more CO2 than fallow lands. The amount of CO2 is, usually much greater near the roots of plants than further away. It may be, due to respiration by roots,, , 3. Microbial activity: The microorganisms in soil require oxygen for, respiration and they take it from the soil air and thus deplete its, concentration in the soil air. Decomposition of organic matter produces CO2, because of increased microbial activity. Hence, soils rich in organic matter, contain higher percentage of CO)., , 4. Seasonal variation: The quantity of oxygen is usually higher in dry, season than during the monsoon. Because soils are normally drier during the, summer months, opportunity for gaseous exchange is greater during this, period. This results in relatively high O2 and low CO) levels. Temperature, also influences the CO, content in the soil air. High temperature during, summer season encourages microorganism activity which results in higher, production of CO>., , Prepared by: Prof. S. B. Aware 44, , _, , , , Scanned with CamScanner
