Response of rainfed upland rice (Oryza sativa) to phosphatic fertilizers in an acid soil

A field experiment was conducted at Ranchi on upland rainfed 'Brown Gora' rice (Oryza sativa L.) during wet season of 1992 and 1993 to evaluate the efficiency of ammonium polyphosphate vis-a-vis other phosphatic fertilizers, viz single superphosphate. diammonium phosphate, mussoorie rockphosphate and mussoorie rockphosphate + single superphosphate (3 : 1) each applied (a(sic) 13 and 26 kg P/ha. Results indicated a significant response of the crop to different P sources. Total P uptake by the crop at 26 kg P/ha was higher than that at 13 kg P/ha. Uptake of P in P-treated plots was 1.5-2.0 times more than that in the untreated plots. Among the different P sources, ammonium polyphosphate, diammonium phosphate, single superphosphate and mussoorie rockphosphate + single superphosphate (3 : 1) were comparable in terms of grain yield. The P recovery varied widely (9.97 42.44%) with different sources. The apparent recovery of fertilizer P was more at lower levels of added P than that at higher levels. Ammonium polyphosphate applied (a) 13 kg P/ha resulted in the highest recovery and crop response (62.60 and 67.44 kg grain/kg P during 1992 and 1993 respectively). indicating that higher return from investment on fertilizer P application is possible in rainfed upland rice with this source.