Residual effect of organic and inorganic nutrient sources on macro and micro nutrient status of rabi greengram under rice-greengram cropping system

Studies on cumulative and residual effects of Integrated Nutrient Management of khraif rice on soil fertility status of rabi green gram was conducted at Regional Agricultural Research Station, Anakapalle during rabi 2009 and 2010. Results revealed that irrespective of the treatments, the organic carbon content observed under cumulative effects were higher than their corresponding residual treatments and the contents were higher in second year than first year. All the treatments meant for cumulative effects recorded higher available nutrient status than their corresponding residual treatments. The increase in mean available nitrogen, phosphorus and potassium contents after harvest of greengram due to cumulative effects was 5.6 & 5.18, 14.36 & 16, 4.14 & 4.3 % during 2009 and 2010, respectively. In case of micronutrients, the percent increase during 2009 and 2010 in cumulative effects over residual effects was, 5.1 & 11.54 (Zn), 2.6 & 5.45 (Fe), 9.5 and 10.1 (Cu) and 2 & 3.53 % (Mn), respectively. Among cumulative and residual effects, cumulative effects performed better and between two years build up was more in second year than first year. Among different treatments, the treatment which received 75 % recommended dose of chemical fertilizers + vegetable market waste @ 2.5 t ha-1 to kharif rice and 50 % chemical fertilizers to rabi greengram) recorded significantly higher available macro and micronutrient status and it was on par with 50 % chemical fertilizers+ vegetable market waste vermicompost @ 2.5 t ha-1 to kharif rice and 50 % recommended dose of chemical fertilizers to rabi greengram) and 75 % chemical fertilizers+weed vermicompost @ 2 t ha-1 to khraif rice and 50 % chemical fertilizers to rabi greengram). The treatment with 100 % chemical fertilizers to kharif rice and 50 % chemical fertilizers to rabi greengram recorded significantly lower available nutrient status, which was significantly lower than the integrated nutrient treatments, but was superior to absolute control.