Contribution of Remobilized Total Dry Matter to Soybean Yield

It is recognized that soybean remobilizes carbohydrates and protein compounds from vegetative to reproductive organs during the last half of the seed filling period. However, reports quantifying how much of final yield is constituted by these remobilized materials under field conditions are lacking. The objective of the current study was to determine the contribution of remobilized total dry matter (TDM) to final yield under field conditions. Using five field studies conducted from 1987 through 1995 near Baton Rouge, LA (30. N latitude), % remobilized yield was determined by using crop growth rate during the final half of seed filling (CGR[R6.2-R7]) to calculate how much of the final 50% of seed weight was contributed by remobilized TDM. The % remobilized yield was then calculated as 100 x (remobilized seed TDM/yield). Results indicated that % remobilized yield varied from 15% to 30% and tended to increase as growing conditions improved and plant size increased. Percent remobilized yield also increased when source/sink ratio declined during the rapid seed filling period (R6-R7). In conclusion, a substantial portion of final yield is derived from remobilized TDM.