Contribution of Water Use Efficiency of Summer Legumes for the Production of Rainfed Wheat

Knowledge about water in soil profile and the efficiency with which crop use this water is essential for replacing conventional summer fallow with the objective to optimize legume-wheat rotation system in rainfed areas. A 2-year field experiments were carried out to assess the effects of rotational systems on crop yield, N(2)-fixation and water use efficiency (WUE) in two different locations of rainfed Pothwar. Two legumes crops (mung bean, Vigna radiata & mash bean, V. mungo) along with reference sorghum Sorghum bicolor were rotated with wheat (Triticum aestivum). The WUE values on N(2)-fixation basis was 25% and 16% higher in mash and mung bean with P fertilization over legumes with out P. WUE on grain basis 2.09 kg ha(-1) mm(-1), was 16% higher than mung bean with P fertilization. Over all 29% increase in grain WUE of legumes was observed in succeeding year. Soil water contents were 31% higher under mash bean fertilized with P than sorghum. Soil water distribution across soil profile showed that maximum quantity of water was found at 60-90 cm depth. Total soil profile water contents were 25 cm 100 cm(-1), under legumes and lower, 23 cm 100 cm(-1), under non-legume sorghum at harvest. Grain WUE of wheat was found 11-44% higher in the plots, which were previously under legumes crops as compared to non-legume sorghum. The P fertilization to legumes increased grain WUE of wheat by 22% compared to that of control. (c) Friends Science Publishers