Response of spring rice to fertilizer practices in rice-rapeseed rotation

Spring rice, the principal crop in the midhills of U.P. [Uttar Pradesh], is sown under rainfed conditions in Mar and harvested in Sep. A short-duration (Oct-Feb) rapeseed (Brassica campestris L. var. toria) was found to fit the intervening period best. But yields are low because farmers use very low amounts of chemical fertilizers (4-5 kg/ha). Farmyard manure (FYM) is the principal source of plant nutrients. The response of spring rice to N and FYM and the residual effect on a succeeding rapeseed crop were studied at Hawalbagh, Almora (1,250 m above mean sea level, average annual rainfall (1,027.3 mm) for three years (1983-86)). The soil was sandy loam (pH 6.2, 0.43% organic C, CEC 22 meq/100 g, 22.7 kg available P (Bray's) per ha, 229.6 kg available K/ha). Two levels of N (0 and 20 kg N/ha) and three levels of FYM (0, 10, and 20 t/ha) were applied only to spring rice, in a factorial randomized block design with three replications. FYM applied the first year had 0.65% N, 0.23% P, 0.60% K, and 18.8% moisture content; in the second year, it had 0.61% N, 0.27% P, 0.58% K, and 16.7% moisture content; and in the third year it had 0.56% N, 0.21% P, 0.65% K, and 15.5 % moisture content. Rice variety VL206 was seeded the second half of Mar and harvested the middle of Sep. Rapeseed variety T9 was planted beginning of Oct and harvested in the second half of Feb. Rice yield increased by 0.14 t/ha with 20 kg N/ha. Yield increase with 10 and 20 t FYM/ha were 0.52 and 0.76 t/ha, respectively. Highest yield was with 20 t FYM and 20 kg N/ha. The residual effect of FYM on the following rapeseed crop was significant. Rapeseed yields were 0.17 and 0.24 t/ha higher with 10 and 20 t FYM/ha, respectively. The residual effect of fertilizer N on rapeseed yield was not significant. Applying 20 kg N with 20 t FYM/ha to spring rice not only increased rice yield, but also doubled yield of the succeeding rapeseed crop.