Yield tended to increase as RS decreased in years of average rainfall, but the differences were not significant. In the southern USA, determinate soybean grown in row spacingsIn an above-average rainfall year, however, a soybean (RS) of 50 cm or less generally produce higher yields than that grown planting system with 25-cm RS outyielded the 100-cm in RS of 75 to 100 cm. However, the Early Soybean Production System (ESPS) commonly employs indeterminate cultivars in environments RS by 17%. Alessi and Power (1982) reported that, in with limited rainfall. This study was conducted to determine whether 2 yr of a 4-yr study, total water use was greatest and RS affects seed yield in the ESPS. Twenty-one field experiments were average soybean yields were least from a 15-cm RS conducted from 1984 to 1997 at sites in Arkansas, Louisiana, and compared with 45-or 90-cm RS. Their data suggested Texas to determine the effect of RS on seed yield in the ESPS. Row that planting in 15-cm rows enhanced water use prior spacings of 80 and 40 cm were compared in seven tests; of 75, 50, and to flowering. They concluded that, in extreme drought 25 cm in six tests; of 75 and 25 cm in one test; of 100, 50, and 25 cm situations, this enhanced early-season water use left less in four tests; and of 100 and 25 cm in three tests. One to five Maturity

The midsouthern USA often experiences a drought from mid‐June through late‐August. Short‐season soybean (Glycine max. [L.] Merr.) cultivars (maturity groups [MG] 00, 0, I, II, III, and IV) were evaluated in narrow rows and at high populations for their ability to avoid drought at several locations in the mid‐South. When planted in early May under nonirrigated conditions, MG 00 and 0 cultivars generally had lower yields than later‐maturing cultivars. Within an irrigation treatment, cultivars from MG I, II, III, and IV generally produced similar yields under irrigated or nonirrigated conditions, but MG I and II cultivars required considerably less irrigation than cultivars from MG III and IV. April and early‐May planting dates required less irrigation and generally yielded more than late‐May or June planting dates for all MG and locations. This research demonstrates that yield potential in the mid‐South is similar for cultivars from MG I, II, III, and IV under favorable conditions, that irrigation needs can be decreased by use of early‐maturing cultivars planted in April or early May, and that risk of exposure to drought can be decreased by including MG I and II cultivars in a nonirrigated, early production system.

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