Soybean Field Losses as Influenced by Harvest Delays

Conflicts for time and machinery can postpone harvests beyond the initial time when optimum conditions exist. This study was conducted to determine the effects of delaying soybean [ Glycine max (L.) Merr.) harvests on grain losses in the field. Field studies were conducted each year from 1983 to 1986 at Arlington, WI. Two cultivars from each of maturity groups (MG) 0, I, and II, one more susceptible to lodging than the other, were used. Initial harvest for each maturity group began 3 to 7 d beyond stage R8. Three additional harvests were made for each maturity group at 14, 28 and 42 d beyond their initial harvest. Average soybean field losses were 10% of the potential yield, but ranged from 5.5% in 1983 to 12.7% in 1984. Loss of potential yield increased linearly at a rate of 0.2% d −1 from an average of 6.1% at the initial harvest to 13.9% 42 d later. In 1984 and 1986 net yields were reduced 14 and 18 kg ha −1 d −1 , respectively. Harvest delays of 42 d resulted in plant deterioration and, in turn, lodging increased 20%, and preharvest, shatter, and stem losses increased 62, 95, and 70 kg ha −1 , respectively. Shatter losses were influenced by moisture conditions at harvest, but plant deterioration also increased shattering beyond that accounted for by moisture. On the average the MG I cultivars Hardin and Northrup King S1346 lost only 7.3 and 8.3% of their potential yield versus 10.4 and 11.4% for the MG 0 cultivars Ozzie and Evans, and 10.8 and 9.2% for MG II cultivars Wells II and Corsoy 79. Both of the MG I cultivars exhibited slower rates of harvest loss increases. The proportion of potential yield lost was inversely related to potential yield, indicating that harvest efficiency was improved with higher yields. Harvest delays can ultimately result in plant deterioration, increased grain losses, increased harvesting difficulties, and reductions in net yield of 11 kg ha −1 d −1 .