Effects of close planting densities on assimilate accumulation and yield of soybean with different plant branching types

Abstract

: To investigate the effects of planting density on leaf area index, dry matter accumulation and distribution, and yield components of different varieties, field experiments were conducted using two soybean varieties with different branching types (Zhongzuo XA12938, a main stem type variety; Zhonghuang 13, a branched type variety) under six planting densities (D1: 13.5×10 4 plants hm –2 ; D2: 18.0×10 4 plants hm –2 ; D3: 22.5×10 4 plants hm –2 ; D4: 13, respectively. Compared to Zhonghuang 13, the high LAI values in Zhongzuo XA12938 lasted longer and decreased less at the middle and late stages. The degree of increase in dry matter with density varied between treatments. At podding stage, dry weight increased by 77.53% and 51.21% in the high-density treatment (D6) compared to the low-density treatment (D1) for Zhongzuo XA12938 and Zhonghuang 13, respectively. The percentage of dry matter in reproductive organs at maturity stage increased and then decreased with increasing density. The highest yields were achieved under D5 (5000.45 kg hm –2 ) treatment and remained stable at increasing densities for Zhongzuo XA12938. The highest yields for both years were achieved under D4 (4477.90 kg hm –2 ) and D5 (3935.30 kg hm –2 ) treatments for Zhonghuang 13. The average yield of Zhongzuo XA12938 was significantly higher by 22.37% than that of Zhonghuang 13. Grey correlation analysis revealed that plant height and effective pods per unit area were closely related to yield in Zhongzuo XA12938, while effective grains per unit area and height of centre of gravity were more highly correlated with yield in Zhonghuang 13. Zhongzuo XA12938 moderate increase in density can increase the LAI and pro-long the duration of its high value, promote dry matter accumulation, increase the proportion of reproductive organs, and improve the yield in soybean. Varieties with strong meristem regulation can be used to improve yields and increase benefits by appropri-ately increasing planting density in production.