Soybean Development and Yield Are Influenced by Planting Date and Environmental Conditions in the Southeastern Coastal Plain, United States

Variation of soybean [Glycine max (L.) Merr] growth and yield with planting date may be a response to changes in the plant, the environment, or a combination of both. This 2-yr experiment studied the effects of planting date on durations of vegetative and reproductive stages, and duration, temperature, and precipitation on yield of five soybean cultivars each representing a maturity group (MG IV-VIII) under dryland conditions. Planting dates were scheduled for 14-d intervals from late April to mid-July, 2008 and 2009. Length of growing season shortened with later planting dates, and the shortening was greater for vegetative stages compared with reproductive stages, especially for later MGs. Duration of flowering decreased with later planting date more rapidly for MG V through VIII (-0.60 to 1.18 d per planting date delay) than MG IV (insignificant). Pod-set duration declined with later planting date slowly for all MGs and insignificantly for MG IV and V in 2008. There was no conclusive relationship between seed-fill duration and later planting date. Duration of vegetative stage was positively correlated with yield of each MG. At flowering stage, yield of MG IV was positively correlated with temperature, while yields of MG V to VIII were positively correlated with duration, temperature, and precipitation. Precipitation during pod-set was the main factor in determining yields of all MGs. Temperature during seed-fill was positively correlated with yields of all MGs. These results suggest that May planting dates would achieve greater yield potential for all MGs by extending duration of development stages and avoiding cooler temperature during seed-fill.