INFLUENCE OF SEASONAL VARIATION ON RADIATION USE EFFICIENCY AND CROP GROWTH OF MAIZE PLANTED AT VARIOUS DENSITIES AND NITROGEN RATES

Crop growth (CG) is a function of leaves exposed to solar radiations and ratio of the radiation intercepted by the canopy, which is termed as radiation use efficiency (RUE). Both CG and RUE of maize planted in spring and summer at three densities (43,000, 53,000 and 67,000 ha^-1) and three N-fertilizer rates (90, 120 and 150 kg ha^-1) were compared in a 3x3 splitplots, randomized complete-blocks design in three replications. The results revealed a significantly (P 0.05) longer (28.6%) pre- and shorter (5.0%) -post anthesis durations for spring than summer planted crop. The density and N-fertilizer rates did not show any significant changes in pre- or post anthesis duration. The CG and RUE were observed to be higher (p 0.05) in summer than in spring. Every increment in the density resulted in significantly (P 0.05) higher CG and RUE. Yield increased by increasing density from 43,000 to 53,000 but remained non-significant (p 0.05) thereafter at density 67,000 ha^-1. Nfertilizer rates 90 and 120 kg ha^-1 did not show any significant (p 0.05) changes in CG, RUE and/or yield, but did increase significantly (p 0.05) the yield at 150 kg ha^-1. As compared to spring crop, interactive effect of treatments (density x N) were found significantly (p 0.05) higher for CG, RUE and yield in summer at N-fertilizer rate of 150 kg N ha^-1 having density of 67,000 ha^-1. The study suggested that phases of crop growth and development were highly influenced by seasons, which affected CG and RUE, and hence the yield. Nevertheless, maintaining desired density of maize is more crucial than to increase N-fertilizer for maximum production in the season. Summer planted maize out-yielded spring crop due to relatively mild cooler weather at crop reproductive phases of the development.