DRYLAND WHEAT YIELD DEPENDENCE ON RAINFALL, APPLIED N AND MULCHING IN PRECEDING MAIZE

To evaluate the response of dryland wheat (Triticum aestivum L.) to mulching in preceding maize and fertilizer N application field experiments were conducted for six years (1980-86) with maize-wheat sequence on a sandy loam soil in northern India. Four rates of N application viz. 0, 40, 60 and 80 kg N ha-1 in wheat were combined with three mulch treatments viz. no mulch (M0), paddy straw mulch (M(p)) and basooti (Premma mucronate) mulch (M(b)) applied at the rate of 4 tons ha-1 on dry weight basis applied three weeks before harvest of maize. Mulching (M(p) and M(b)) increased (profile) stored moisture at wheat seedling by 31 to 88 mm. Mb also increased NO3-N content by 33 to 42 kg ha-1 in 0-120 cm profile over M0 and M(p). Over the years, M(p) increased wheat yield by 11 to 515 kg ha-1 and M(b) by 761 to 879 kg ha-1. Wheat yield response to mulching was related to rainfall pattern during its growth season. Significant response to mulching was obtained only in years when rainfall during vegetative phase of the crop was low. Amount and distribution of rainfall during two main phases of crop development affected the N use efficiency by wheat. On an average, each cm of rain substituted for 3.5, 4.6 and 6.5 kg of applied N ha-1 under M0, M(p) and M(b), respectively. Split rainfall for two main phases of crop growth, available stored water at seeding, fertilizer N and profile NO3-N content accounted for 89 per cent variability in wheat yield across years and mulchin treatments.