Effects of Sowing Date on Yield and Quality of Summer-sown Soybean in South China

Three nationally-certified summer-sown soybean cultivars adapted to grow in South China were planted at five sowing times in Guangzhou to determine optimal sowing time and effects of sowing time on agronomic traits,yield,protein and oil contents of seeds.The results indicated that sowing time had significant effects on the soybean yield and quality.And the optimal sowing period was from mid-June to early July.The yield,plant height,number of pods or seeds on main stem,number of pods or seeds on branch had a significant tendency of gradually decreasing with the delay of sowing time,and different soybean genotypes varied in the extent of this decreasing tendency.In late July sowing,there was a need to increase the sowing density and apply some irrigation to protect the late-maturing or late-sown varieties from drought stress.When cultivar Huaxia 3 was planted under the optimal sowing time,there were more pods or seeds on branches than main stem.Therefore a reasonable density for this variety should be adopted in order to increase yield of whole plant.