Influence of irrigation and growth stage on element concentrations of soybean plant parts

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Abstract
A three‐year field study was conducted to determine the influence of irrigation on the nutrition of the “Lee 74” cultivar, a determinate soybean (Glycine max (L.) Merr.). The objectives were to measure seasonal concentrations of N, K, Ca, and Mg in steins, leaves, and pods for soybeans grown on a Crowley silt loam (Typic Albaqualf) and a Kobel clay (Vertic Fluvaquent) under irrigated and nonirrigated moisture regimes. Fluctuations in element concentrations in relation to plant growth stage for irrigated and nonirrigated leaves and stems were modeled using multivariate regression. Elements in the pods as effected by irrigation and growth stage were also compared. During 1974, a wet year, element concentrations of the leaves, stems, and pods were unaffected by irrigation. In the dry years of 1975 and 1976, significant differences in the concentration of N, K, Ca, and Mg in the plant component parts were found due to irrigation. Generally, element concentrations of stems, leaves, and pods of irrigated plants were greater than those of water‐stressed stems, leaves, and pods at several growth stages. Element concentrations in stems and leaves that were significantly affected by irrigation also were reflected in the pods, Regression models generally accounted for the majority of the seasonal element variation. Irrigation improved the predictability of the K and Ca regression models.