Effect of Planting Date On Maturity Group VII and VIII Soybean Growth, Development, and Yield Under Different Row Patterns in South Carolina.

Planting date (PD) plays a significant role in soybean (Glycine max (L.) Merr.) growth, development, and grain yield; therefore, a 2-yr experiment was initiated to determine the effects of PD and row pattern (RP) on maturity group (MG) VII and VIII soybeans planted from June 15 to July 7th at weekly intervals under dryland conditions. Field studies were conducted at two locations: the Clemson University Edisto Research and Education Center (REC) near Blackville, SC; and the Clemson Pee Dee REC near Florence, SC. Pioneer 97M50 (MG VII) and Prichard RR  (MG VIII) soybeans were planted in both 2011 and 2012. Row Pattern consisted of a strip-tillage system on 96-cm row spacing and a no-till system with drill spacing of 19-cm. Based on analysis of the two trials at the Edisto REC, grain yield for the MG VIII cultivar was higher than the MG VII cultivar when averaged across PD and RP. The soybean yield in the strip-tillage system was significantly higher when compared to the yield in the no-till drill planting system when averaged over PD and MG. Delayed PD showed a decreasing trend of grain yield; however, the difference was not significant. Data from the trial at the Pee Dee REC in 2012 was not included in this analysis, but will be included in the presentation. Delayed PD significantly decreased the duration of vegetative and reproductive growth for both MG VII and MG VIII soybeans, respectively. Duration of vegetative growth, Normalized Difference Vegetation Index, Leaf Area Index and plant height at R2 and R4 showed positive correlations with grain yield at the Edisto REC. These results showed that grain yields were affected by PD and RP for both MG soybeans. In general, delayed PD negatively affected vegetative growth and shortened the overall growth period, which contributed to lower grain yield.