An Early Soybean Production System for Drought Avoidance

Abstract

Late summer drought during seed formation often limits yield of soybean [Glycine max (L.) Merr.] grown in the southern U.S. A field study was conducted to determine if earlier planting of early-maturing varieties could avoid periods of drought stress by having their reproductive development coincide with periods of greater available moisture. Varieties in Maturity Groups (MG) III to VII were planted in mid-April and in mid-May near Blossom and Hooks, TX, from 1986 to 1988. There were significant year and location effects on yield. Two MG III varieties planted in April 1986 at Blossom yielded eight times more than the MG V to VII varieties. Negative correlations were found between yield and maturity date in 1986 and 1987. Early drought stress in 1988 reduced yields about 30% for the April-planted MG III and IV varieties, but yield was again negatively correlated with maturity date. Yields at the Hooks site were up to 45.8 bu/acre higher than those at Blossom, but they were also negatively correlated with maturity date in the April 1986 planting. The seasonal rainfall at Hooks in 1987 was less than half that of 1986 resulting in varietal yields from the early planting being reduced from 8.3 up to 47.1 bu/acre. A negative correlation was still found between maturity date and yield. In 1988, however, late-season rainfall resulted in a positive correlation between yield and maturity for the April planting. Results from this study show that an early soybean production system using adapted MG III and IV varieties can avoid the effects of late summer drought and result in acceptable yields