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Development of Double-Crop Soybean under Different Soil Water Regimes

Pearce, R. C., Grabau, L. J., Grove, J. H., Lin, H.
Agronomy journal 1993 v.85 no.3 pp. 576-583
Glycine max, double cropping, Triticum aestivum, soil water content, crop yield, seeds, rain, dry environmental conditions, water stress, drought, sowing date, Kentucky
Double-crop soybean [Glycine max (L.) Merr.] comprises nearly one-third of the total soybean hectarage in the southeasteirn USA. This study was initiated to investigate the water relations of soybean following winter wheat [Triticum aestivum (L.) emend. Thcll], with emphasis on the role of stored soil water. A treatment scheme was devised in which wheat was killed at heading, mid-grain fill, and maturity, resulting in three different levels of stored soil water at soybean planting. In 1986, soil water levels at planting were 26.0, 23.1 and 21.4 cm of water in the 0.9-m profile, respectively. A relatively dry early summer resulted in poor soybean stands and slow early growth; however, rainfall was well distributed during the latter half of the growing season. Soybean yields in 1986 were 2.76, 1.60, and 0.44 Mg ha⁻¹, respectively. Initial soil water levels in 1987 were 31.1, 27.5, and 25.1 cm of water in the 0.9-m profile. A wet early summer resulted in good stands and vigorous early growth, but a late summer drought caused severe stress during the reproductive growth period. Soybean yields recorded in 1987 were 0.97, 0.54, and 0.30 Mg ha⁻¹, respectively. In 1989, soil water levels at planting were 33.1, 34.3, and 31.6 cm and associated yields were 1.51, 1.81, and 1.11 Mg ha⁻¹. Rainfall was above average and well distributed during the 1989 season. Within each of the years there was a positive relationship between soil water level at planting and yield of double-crop soybean; however, between years the amount and distribution of rainfall had a more dominant influence on yield than did soil water level at planting. Contribution from the Kentucky Agric. Exp. Stn. as Journal Article no. 92-3-5.