Crop yield, disease incidence, and insect pest attack in relation to N dynamics in rice

Abstract

The decline in rice yield on the Indo-Gangetic plains is a matter of great concern (Abrol et al 2000). We evaluated available soil N, plant N content and uptake during rice growth, and incidence of major diseases and insect pest attacks in an ongoing long- term experiment (since 1982) at the PAU farm (30° 562 N and 75° 272 E). The experimental site is characterized as semiarid subtropical, with soil pH of 8.1, electrical conductivity of 0.18 dS m-l , 0.21% organic carbon, 3 kg NaHC03-extractable P, and 93 kg NH40ac-extractable K ha-l. The fertilizer treatments were a control; application of recommended optimum (100%) and supra-optimal (150%) amounts of N, NP, NPK, NPKZn; half N through Sesbania aculeata green manure (GM) and the rest through urea; and one-third N through farmyard manure (FYM) and the rest through urea plus recommended amounts of PKZn. The recommended amounts of N, P, K, and Zn were 120, 30, 30, and 3 kg ha-l, respectively. Nitrogen was applied in three equal amounts at transplanting and at 3 and 6 wk after transplanting, whereas all of P and K were drilled at puddling. The experiment was laid out in a randomized block design with six replications.