Saturday, 15 July 2006

Development of Biofertilizer Package for Rehabilitation of Degraded Forestland and Enhancement of Soil Organic Carbon in North India.

Prity Sagar Sr. and Ravindranath N.H. Indian Institute of Science, Mallaswaram, Bangalore, India

In developing countries, the paramount challenge is to rehabilitate the vast degraded land to produce adequate quantity of food, fodder, fuelwood etc. for the increasing population. The frequent and disproportionate use of chemical fertilizer, deforestation, and human population growth contribute to land degradation. The National Commission on Agriculture (1976)and Ministry of Agriculture (1982) both estimated that 175 Mha of land were wastelands. However, the Wastelands Atlas of India prepared by National Remote Sensing Agency (2000) shows about 63.85 Mha lands were degraded out of these 14.06 Mha comes under degraded forest land. Biofertilizer package containing the microbial inputs and organic manure could lead to increased plant productivity, reduce emission of greenhouse gases, improve environmental quality and arrest further degradation. Arbuscular Mycorrhizal Fungi (AMF) are known to establish strong mutualistic and symbiotic relationship with the living roots of litchi plants to the extent of mycorrhizal dependency. AMF have potentiality to provide better sustenance to the plants even in adverse conditions by enhancing the mobility of ions/nutrients from the depletion zone of soil. However, dual inoculation with Azospirilum brasilense exerts a synergistic effect on plant growth. The present investigation has been carried out with an aim to develop a biofertilizer package i.e., VAM, A. brasilense and VermiCompost (VC) to obtain better growth of four varieties of litchi plants Viz., Desi, China, Shahi and Purbi, commonly grown in northern part of India and enhancing the soil organic carbon. The effect of bio-inoculants along with vermicompost on plant growth performance of litchi plants was evaluated in terms of plant height, shoot length, stem diameter, canopy coverage, and leaf surface area. The maximum % increase in plant height i.e., 77%, and 158% was recorded in tripartite combination (VAM + A.brasilense + vermicompost) in Desi and China varieties. In case of shoot length, maximum percent increase was recorded in Desi and Purbi varieties, 66.52% and 195.07%, respectively when treated with A. brasilense + AMF. China, Shahi and Purbi achieved maximum growth in stem diameter under VC + VAM + A. brasilense treatment. The maximum canopy coverage was recorded in variety Purbi in tripartite combination (VAM+A.brasilense+ vermicompost), followed by China and Desi varieties. The maximum leaf surface area was recorded i.e., 181%, 191% and 210% in Var. Desi, Shahi and Purbi respectively in tripartite combination (VC + VAM + A. brasilense) followed by China. On comparison of results, it was evident that the marcots treated with indigenous AMF and A. brasilense along with equal doses of vermicompost showed best growth in all the varieties expect Shahi. After one year of treatment, the soil organic carbon recorded was maximum in tripartite combination. Thus the biofertilizer package not only helps improve production of horticultural crops but also improves soil organic carbon, as mentioned earlier. This improved soil fertility status could therefore enhance yield of crops as well as arrest degradation.

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