Influence of Long Term Application of Farm Yard Manure and in situ Green Manures on Crop Productivity and Soil Organic Carbon under Rice-Rice System in a Typic Haplustalf

The effect of long-term application of inorganic fertilizers and organic materials (farmyard manure, in situ green manuring with daincha) on rice productivity, soil organic carbon and nutrient availability was analysed at Regional Agricultural Research Station, Pattambi, Kerala Agricultural University. 15 year rice-rice cropping system experiment consisted of twelve treatments including control, inorganic fertilizers alone and fertilizers along with organic materials such as farmyard manure (FYM) and in situ green manuring with daincha. Long term fertilizer experiments (LTFE) provide an opportunity to evaluate the sustainability of agricultural practices. Integrated nutrient management and in situ green manuring with daincha recorded higher grain and straw yields and in situ green manuring was identified as a cost effective and farmer friendly technology. The organic carbon content (%) in soil in 100 per cent NPK+ FYM plot and that in 100 per cent NPK+ in situ green manured (daincha) plot was higher than the plot receiving inorganic nutrients alone. In addition to high productivity, these also had retained soil fertility.