Importance of Soil to Biosphere

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Soil plays an exceedingly important role in determining the nature and composition of biosphere which develops on it. Most of our necessities are fulfilled by the communities of plants and animals which develop on it. Fertile soil is a natural resource of fundamental importance. Important attributes which enable a soil to perform its multifarious roles are: 1. Soil is a solid stratum underneath which provides mechanical support to the plants. Plants and animals including man live on it. 2. Its porosity and the moisture-holding capacity enable it to retain rain water or the water flowing over or through it for long durations. In drier periods, soil serves as a reservoir of water on which a number of living organisms depend for their water requirement. Even when land surface is completely dry plants can obtain water through their roots which go deep into the soil. 3. Ion-exchange capacity of the soil is responsible for retaining micro- and macro-nutrients in the soil for long durations. The colloidal component which consists of clay micelles and humus particles (smaller than 0.002 mm in size) tightly binds a number of ions to their surface. Water carrying useful ions through the soil distributes them evenly. Lower concentration of nutrient ions following active uptake by plants causes these ions to be released into the soil solution. So ion-exchange capacity of the soil ensures even distribution and availability of nutrients as and when required by plants. It is also helpful in preventing excessive leaching of nutrient ions while maintaining an appropriate pH which directly influences nutrient availability and the growth of plant, animals and microbes. 4. Decomposition and mineralization of organic matter and regeneration of nutrients is another very important role of a fertile soil. Soil contains organotrophic bacteria, nitrifying bacteria, pigmented

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