Soil degradation & forest soils : Extensive studies were undertaken in Simlipal National Park, India, on the chemical changes that occur on deforestation and cultivation The study revealed that deforestation and cultivation result in statistically significant reduction in organic carbon, total nitrogen, C:N ratios, cation exchange capacity, available calcium and magnesium. However, there are no significant changes in total and available phosphorus, available potassium and sodium; C:P and N:P ratios are reduced. Loss of organic carbon and nitrogen occurs rapidly in the first 15 yearsof cultivation and reaches quasi-steady state values around 1-2% organic carbon and 0.1-0.2% nitrogen. Extent of reduction is not related to initial levels. Evergreen forest soils have the highest levels of organic carbon and nitrogen, followed by deciduous forests, grasslands and cultivated lands in that order. Cation exchange capacity, total exchangeable bases, exchangeable calcium and potassium levels are also highest in evergreen forest soils; deciduous forests, grasslands and cultivated soils have statistically similar contents of bases. Exchangeable magnesium is not affected by vegetative cover. Cultivation causes some reduction in acidity but there is no reduction in clay content of the soil. Cultivated soils contain much less moisture than the adjoining forest soils and evergreen forest soils have the highest moisture contents.
It is concluded that soil organic matter, moisture and cation exchange capacity are the key factors of soil exhaustion. The removal of green forest canopy results in a cessation of litter input and drying of the soil. Thereby, conditions for optimum turnover of humus are no longer present, organic carbon and nitrogen are lost to the atmosphere, soil exchange capacity is lowered with loss of calcium and magnesium.

Organic agriculture:

Techniques of organic agriculture, including soil nutrient management and pest management, are being developed for various crops. A successful system has been developed for pulses (gram) using readily available materials and in-house generated materials. Yields are good and the seed has significantly higher N content. A suitable technique is now being developed for rice.

        1. Ghosh K and Varadachari C. (2006) Organic farming : A reformed traditional agriculture. Invited Lecture delivered at the Seminar on “Organic Farming : Resurgence of Traditional Agriculture, 2006, Calcutta, by Ministry of Agriculture Government of India.
      2.  Varadachari C and Ghosh K (2005) Organic farming in improving soil fertility, In National Policy on Promoting Organic Farming (Eds. P. Bhattacharyya & D. Kumar) National Centre of Organic Farming (Government of India), Ghaziabad, 40-43.
      3. Effects of deforestation and cultivation on soil CEC and contents of exchangeable bases : A case study in Simlipal National Park, India : H. Saikh,C. Varadachari  &  K. Ghosh  :  Plant & Soil (Netherlands)  204 : 175-181 (1998).
        4.  Changes  in  carbon, nitrogen and phosphorus levels due to deforestation and cultivation : A case study in Simlipal National Park, India : H. Saikh,C.Varadachari &   K. Ghosh : Plant & Soil (Netherlands) 198 : 137-145 (1998).