Effect of Late Planting on Maturity Group VII and VIII Soybean Under Different Management Systems in South Carolina.

Planting date plays a significant role in soybean (Glycine max (L.) Merr.) production. The objective of the study was to evaluate the effect of late planting date (PD) and management system (MS) on maturity group (MG) VII and VIII soybean. This experiment was conducted at Clemson University, Edisto Research and Education Center (REC) under dryland conditions. Soybean Pioneer 97M50 (MG VII) and Prichard Roundup (MG VIII) were planted on 15 June and then once a week for four weeks. The management systems consisted of strip-tillage with 96 cm row spacing and no-till drill with 19 cm row spacing.  Generally, grain yields decreased after PD 2 for MG VII and VIII planted in no-till and strip-till, respectively, while yield increased for PD 2 and 3 of MG VII soybean planted in strip-till. Relatively smaller yield variations were recorded for drilled soybeans over planting dates for MG VIII. The time from planting to reproductive (R) growth stages decreased with later planting dates and was slightly higher for MG VIII than VII soybean. However, length of stages was not affected by management system. Positive relationships were observed between plant height, normalized difference vegetation index (NDVI), and leaf area index (LAI) for some selected R stages (R1, R3, and R5). These results indicate that grain yields may be affected by planting date, planting method, and MG and generally less with delayed PD due to reduced length of growth stages and plant growth. However, choosing the right MG and MS may help to reduce the detrimental effects of late PD on soybean.