Drought Response of Grain Legumes Under Irrigation Gradient: I. Yield and Yield Components1

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Abstract
Food legumes are widely grown as a source of protein in semiarid and tropical regions, but production is often limited by the large variation in the amount and distribution of rainfall. Mungbean (Vigna radiata L.), cowpea (Vigna unguiculata L.), soybean (Glycine max L.), and peanut (Arachis hypogeae L.), often planted after rice (Oryza sativa L.), were compared for response to a season‐long moisture stress on medium‐deep Tropudalf soil, using a line‐source sprinkler irrigation system during the January to April 1982 dry season. Drought stress reduced seed yield of all four food legumes, but the reduction due to water stress was greater in mungbean followed by soybean, cowpea, and peanut. Mungbean produced significantly lower yields at all moisture levels than the other legumes. Total water use by peanut was highest, followed by cowpea, soybean, and mungbean. Among yield components, the numbr of pods per square meter was most affected by water stress in all four species, followed by number of seeds per pod, while seed weight was least affected. Harvest index decreased Linearly with increasing levels of drought for all four species.