Influence of Planting Date On Maturity Group IV – VIII Soybeans Grown in the Southeastern U.S.

Optimum planting dates for different maturity group (MG) soybeans [Glycine max (L.) Merr.] can help to increase soybean yield potentials. The objective of this study was to find the optimum planting dates for maturity group (MG) IV through VIII soybeans. This 2-yr research project was conducted at Clemson University, Edisto Research and Education Center near Blackville, SC. Soybean planting dates on all MG started after mid April and continued every 2 weeks until mid July. Plants were planted at recommended seeding rates. Most MG soybeans yielded relatively higher for April through early June plantings. However, soybean yields decreased following early June planting. The time from planting to R1, R6, and R8 growth stages decreased with delayed planting dates for all MG soybeans. Shortening reproductive growth stages with later planting dates for MG IV – VIII soybeans contributed to lower yields due to shorter growth period. These results indicate that optimum time for planting most MG soybeans is from early May till about 20 May. Also, the planting should be completed by early June for later planted soybeans (for example as double-crop with small grains).