Evaluation of Critical Shattering Time of Early-Maturity Soybeans Under Early Soybean Production System.

One of the major problems associated with early soybean production system (ESPS) in the Midsouth is seed quality and shattering of early MG soybeans that mature in the mid-summer. Limited information is available to measure the impact of these problems and to provide the management strategies. Study was initiated to investigate the shattering problem of MG IV soybeans, the dominate soybean group in ESPS. The objectives of this study were to determine the pattern and critical point of shattering for majority MG IV soybeans under various climate conditions in the Mississippi Delta. Total 56 and 80 MG IV soybean varieties were used for the experiments in 2006 and 2007, respectively.  The varieties were selected from Mississippi Soybean Variety Trial in correlated years. In 2006, only early planting (April 19) on irrigated field was investigated. In 2007, experiments were conducted on both irrigated and non-irrigated fields. On the irrigated tests, both early planting (April 23) and late planting (May 15) were examined. Preliminary data from both years indicated that most pods of early MG IV soybean varieties could hold seeds for the first three weeks after maturity. However, the differences showed during the fourth week. Non-irrigated soybeans shattered faster than that of irrigated soybeans after three weeks. Irrigated soybeans held seeds longer than that of non-irrigated soybeans within four weeks; however, seed shattering became greater after four weeks. Pods of late planted soybeans held seeds better with the same period after maturity (up to 6 weeks or longer) when they were compared with early planted soybeans on the irrigated field. Late matured seeds tend to have better resistance to shattering most likely due to lower temperatures after late September.