Nitrogen accumulation and partitioning by three grain legumes in response to soil water deficits

Abstract

Few experiments have been conducted to compare the partitioning and accumulation of nitrogen (N) in plant components of grain legumes grown under different soil water regimes. The objective of this study was to determine the effect of soil water deficit on N accumulation and partitioning in soybean ( Glycine max L. Merr.), pigeon pea ( Cajanus cajan L.), and peanut ( Arachis hypogaea L.). In 1984, the three legumes were subjected in a field environment to either well-watered or water-stressed treatments. Nitrogen concentration, total N accumulation, and N partitioning were determined throughout the growing season by measuring N content and concentration in leaves, stems, pod walls, and seeds. Peanut accumulated more total N than either soybean or pigeon pea under both the well-watered and water-stressed treatments. Water stress decreased both N concentration and total N accumulation, especially in soybean and pigeon pea. Less remobilization of N occurred in soybean leaves and stems during the seed-filling period in the stressed treatment because the water stress limited pod addition and subsequent seed demand for N. Loss of N from leaves during seed growth was greater in the crop with the most senescent growth habit (soybean), and lowest in the non-senescent but determinate crop (pigeon pea). Although peanut does not exhibit rapid leaf senescence during seed maturation as does soybean, considerable loss in leaf N was also observed in peanut leaves during the seed-filling period. Soy-bean, peanut, and pigeon pea differed in accumulation and partitioning of N under water-stressed and non-stressed environments. The partitioning and remobilization of N was dependent on the growth habit of the species and was significantly influenced by soil water deficits.