Growth of ‘Braxton’ Soybeans as Influenced by Irrigation and Intrarow Spacing
1985
Ramseur, E. L. | Wallace, S. U. | Quisenberry, V. L.
Achievement of maximum crop yields necessitates the study of factors influencing yields. The influence of irrigation regime and plant population on growth of a Group VII determinate soybean [Glycine max (L.) Merr.] was measured to determine if a particular growth pattern would result in increased yield. In 1980 and 1981, ‘Braxton’ soybeans were grown in 0.91-m rows on a Cecil sandy loam (clayey, kaolinitic, thermic Typic Hapludults) under full-season irrigation (FSI), irrigation beginning at bloom (BI), and no irrigation (NI). Intrarow spacings ranged from 43 or 61 to 457 mm. At growth stage R2, FSI, BI, and NI plants had attained 72, 66, and 75%, respectively, of maximum height and 38, 35, and 55%, respectively, of maximum vegetative dry weight. Height, stem diameter, and dry weight were greater in the irrigated treatments than in NI. Fullseason irrigated plants were generally taller than BI and NI plants and had 1.7 times more dry weight at R2. With increasing spacing, height decreased while stem diameter increased. Vegetative weight was maximized at spacings of 76 mm or less. Development of canopy cover and LAI was more rapid with decreasing spacing and with irrigation. At least 90% canopy closure was obtained in all spacings of FSI and BI, whereas only 59% was achieved in NI. Yields were the same for FSI and BI, and, within irrigation treatments, there were no yield differences among spacings of 305 mm or less. We conclude that comparable yields can be obtained within a wide range of growth patterns, and that severe reductions in vegetative growth at R2 may have little influence on yield if water is supplied thereafter.
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