Topping at the Seedling Stage Changes the Plant Morphology and Yield of Unbranched Type Soybean

Abstract

The crop will be free from the control of apical dominance and the axillary buds will develop into branches after topping. However, there are relatively few studies on this subject of soybean. In order to further improve soybean grain yield, unbranched type high-yield soybean variety was used as test material, and the effects of topping at the first trifoliate stage on soybean plant growth, dry matter accumulation, yield and yield components of five planting densities [15 (D1), 18 (D2), 21 (D3), 25 (D4) and 30 (D5) × 104 plants ha⁻¹] were systematically investigated in this study. The results showed that, the dry matter accumulation increased after topping. Flower number per plant, seed number per plant, pod number per plant, and single-plant yield decreased in conventional-cultivation planting density (D4, topping), but they all increased as the planting density was reduced. D2 achieved the highest yield, with 100-seed weight and yield increased by 8.92% and 5.90% compared to CK (D4, nontopping). The number of branches per plant was significantly and positively correlated with podding node number per plant, flower number per plant, pod number per plant, and seed number per plant. This study demonstrates that the more branches formed after topping, the more conducive to increasing the flower number per plant, pod number per plant under lower density.