NUTRIENT BALANCE STUDIES IN THE SOILS UNDER INTENSIVE RICE – RICE SYSTEM

Cultivating rice – rice sequence in soils over years significantly depleted soil available nutrient status. Among the major nutrients, K was depleted heavily (45 %) followed by N (18.8%), P (12.3 %) and with micronutrients, Zn and B depletion was marked while others were maintained sufficiently in the soil. Marked influence of seasons on nutrient removal by rice was observed in kharif than in rabi which indicates the poor mineralization and utilization of nutrients during wet season.  Management strategies such as addition of micronutrient mixtures and green manure enhanced the yield, nutrient availability, plant nutrient absorption and removal regardless of soil types. Nutrient balance studies carried out for all 20 sites after three years of rice cropping showed negative balance of NPK and S regardless of soil type and management strategies. Except B all other micronutrients were found in positive balance in heavy textured Anaimalai and Palladam soil series and in light textured Irugur series, Zn, Cu and B were observed to be negative in balance. Hence careful monitoring and management of N, K, Zn and B in the rice growing soils is very much essential to achieve higher productivity and maintains soil fertility.