DIRECT AND RESIDUAL EFFECT OF PHOSPHORUS IN RICE (ORYZA SATIVA)-WHEAT(TRITICUM-AESTIVUM) SEQUENCE UNDER SOUTH GUJARAT CONDITIONS

An experiment was carried out for 5 consecutive years (1988-89 to 1992 -93) to study the phosphorus requirement of rice (Oryza sativa L.)-whe at (Triticum aestivum L. emend. Fiori and Paol.) sequence on clayey so il at Bardoli, Surat (Gujarat). The treatments consisted of 0, 50 and 100% recommended dose of phosphorus fertilizer to each crop. Rice resp onded up to 100% recommended dose (50 kg P2O3/ha), whereas wheat showe d significant increase up to only 50% recommended dose (30 kg P2O5/ha) . The residual effect of P applied to each preceding crop had positive and significant effect on the yield of succeeding crop when applied @ 100% recommended dose. The interaction effects of directly applied an d residual P were significant in both the crops. The highest net monet ary return was obtained with 100% recommended dose to rice and with 50 % recommended dose to wheat, indicating 50% reduction in P requirement of wheat in rice-wheat sequence.