Abstract
Field experiments with sorghum-rice rotation were conducted during 1985-1986 and 1986-1987 in a P-deficient Alfisol. The dry weight of leaves plant-1; 1000-grain weight; grain yield ha-1; N, P, and K uptake; and apparent recovery of P (ARP) of sorghum were appreciably higher when the irrigations were scheduled at 60% available soil moisture (ASM) compared to 20% ASM. Plant height, vegetative yield components, grain yield, and NPK uptake by sorghum showed significant increases with P application ranging from 17 .5 to 35.0 kg P ha-1. The grain yield of the succeeding rice crop also showed significant increase due to the residual P applied to sorghum in 1986 at 35 and 52.5 kg P ha-1. Irrespective of residual P levels, application of 10.87 and 21.74 kg P ha-1 to rice appeared essential and thus both crops in rotation need P fertilization in Alfisols for higher productivity. With an application of 35 kg P ha-1 to sorghum, the mean total ARP in the crop rotation was 17.44% in which sorghum and rice accounted for 14.09 and 3.35%, respectively.
