RESPONSE OF DRYLAND WHEAT TO FERTILIZER NITROGEN IN RELATION TO STORED WATER, RAINFALL AND RESIDUAL FARM YARD MANURE

Yield response of dryland wheat to fertilizer N application in relation to components of seasonal water (available soil moisture and rainfall) and residual farm yard manure (FYM) was studied for five years (1983-84 to 1987-88) on a maize-wheat sequence on sandy loam soils in Hoshiarpur district of Punjab, India. Four rates of N viz. 0, 40, 60 and 80 kg ha-1 in wheat were superimposed on two residual FYM treatments viz. no FYM (F0) and 15 t ha-1 (F-15) to preceding maize. FYM application to maize increased the residual NO3-N content by 19-30 kg ha-1 in the 180 cm soil profile. For a given moisture distribution, F-15 increased attainable yields. Over the years, F-15 increased wheat yield by 230 to 520 kg ha-1. Response to fertilizer N was lower in FYM amended plots than in unamended plots. Available soil moisture at wheat seeding and amount and distribution of rainfall during the vegetative and the reproductive phases of crop development affected N use efficiency by wheat. Available soil moisture at seeding alone accounted for 50% variation in yield. The residual effect of FYM on wheat yield could be accounted for by considering NO3-N in 180 cm soil profile at seeding. The NO3-N and available soil moisture at wheat seeding along with split rainfall for two main phases of crop development and fertilizer N accounted for 96% variation in wheat yield across years and FYM treatments.