Evaluating the effect of phosphatic fertilizers on soil and plant P availability and maximising rice crop yield

A laboratory experiment was taken up to evaluate the effects of P sources viz., Mussoorie rock phosphate (MRP), single super phosphate (SSP) and complex fertilisers (20:20:0 and 15:15:15) on availability and release pattern of P for a duration of 60 days in two sets of samples from soils of low and high status of available P from the rice dominant tracts of Vadipatti block of Madurai district. Among the treatments imposed, SSP and FYM incubated soils registered maximum release of Olsen - P of 163.3 and 184.3 mg kg-1 in soils of low and high available P status respectively. A field experiment was taken up in the farmers field at Irumbadi village of Vadipatti block of Madurai district during rabi 2013 with rice (var. ADT 39) as test crop to evaluate the influence of P sources and forms (SSP and complex P with and without PSB) on soil nutrient status, uptake and crop yield. Among the P sources, 20:20:0 and PSB followed by 20:20:0 alone proved significantly superior to SSP and farmer's fertilizer practice of DAP application. It was noteworthy to observe that 100 % and 50 % of recommended P as SSP were on par in influencing the available P status and yield of rice crop indicating the scope for reducing 50 % of P in soils of high P availability.