The researchers studied how different planting dates affect the yield of sprout soybean. They planted six soybean varieties on three different dates in 2000 and 2001. They found that late planting decreased the number of seeds and pods per plant, leading to lower yields. The soybean yield was highest when planted on May 25 compared to later dates. In 2000, factors like number of branches and dry weight were positively correlated with yield, while in 2001, factors like stem thickness and leaf area were important for yield. Late planting had a bigger impact on some soybean varieties than others.