ABSTRACT
Soil is the most biologically diverse component of the global environment. Soil borne organisms directly influence ecosystem services, and hence crop-based agricultural productivity and sustainability. Soil is the naturally occurring heterogeneous unconsolidated mineral and organic material at the earth's surface, and can be characterized in terms of its biological content, physical nature or chemical constituents. Microorganisms contribute significantly to cycling/recycling of mineral nutrients and carbon in the soil and through their activities; nutrients can become more or less available to crops. Mineralization is the process by which soluble and insoluble organic matter is converted into inorganic forms available for plant uptake. Bulk soil is known to have significantly less biodiversity than is found in the rhizosphere. Soil microorganisms can directly compete with plants for nutrients in the soil. Insect and mite pests pose a significant and persistent threat to crop performance in tropics, and the choice of method selected by farmers to mitigate these challenges impacts directly upon soil biodiversity.
