Effects of Delayed-Harvest on Seed Quality and Final Yield of Maturity Group IV Soybean in the Mississippi Delta.

Maturity group (MG) IV soybean is a major MG type used in the Early Soybean Production System (ESPS). Delayed harvesting due to environmental conditions is a major problem for MG IV soybeans.  Experiments were conducted at the Delta Research and Extension Center at Stoneville, MS to investigate the effect of delayed-harvest on yield and seed quality (seed shattering and seed composition) of MG IV soybeans in 2008. Two varieties, AG4403, an early IV MG, and AG4903, a late IV MG, were planted in late April and mid-May. Plants were harvested approximately three weeks and six weeks after maturity. Results indicated that timely harvest soybean after maturity (within three weeks) is one of the critical factors to obtain high yield. Delaying harvest significantly affected final yield under certain circumstances. In late-April planting, yield of AG4403 was reduced 27% when harvest delayed to six weeks after maturity (WAM) compared with those harvested at three WAM. However, no significant yield reduction was observed due to delayed-harvest for May planting in AG4403 and for both plantings in AG4903. The yield lost from delayed-harvest in AG4403 was a direct result of seed shattering after maturity due to unfavorable temperatures. It indicates that it is critical for April-planted early IV soybeans to be harvested within three to four weeks after maturity to minimize the yield lost caused by seed shattering. Germination rates were not significantly different between normal and delay-harvested seeds, but germination rates of most seeds were not up to commercial standards.  Effects of delayed-harvest on seed composition will be further examined.