Abstract
Increasing planting density is one of the key management practices to enhance soybean yield. A 2-yr field experiment was conducted in 2018 and 2019 including six planting densities and two soybean cultivars to determine the effects of planting density on branch number and yield, and analyze the contribution of branches to yield. The yield of ZZXA12938 was 4389 kg ha−1, which was significantly higher than that of ZH13 (+22.4%). In combination with planting year and cultivar, the soybean yield increased significantly by 16.2%, 31.4%, 41.4%, and 46.7% for every increase in density of 45,000 plants ha−1. Yield will not increase when planting density exceeds 315,000 plants ha−1. A correlation analysis showed that pod number per plant increased with the increased branch number, while pod number per unit area decreased; thus, soybean yield decreased. With the increase of branch number, the branch contribution to yield increased first, and then plateaued. ZH13 could produce a high yield under a lower planting density due to more branches, while ZZXA12938 had a higher yield potential under a higher planting density due to the smaller branch number and higher tolerance to close planting. Therefore, seed yield can be increased by selecting cultivars with a little branching capacity under moderately close planting.
Highlights
Soybean, an important raw material in vegetable oil, protein-rich human food, and animal feed, plays an important role in global food security [1,2]
We proposed the following hypothesis: (1) high density planting can significantly increase soybean seed yield, (2) the number of soybean branches decreased with the increase of planting density, and (3) the increase of yield contribution rate of mainstem was the main reason for yield increase under dense planting
The hundred-seed weight was significantly 31.4% lower in ZZXA12938 compared with ZH13, indicating that the high yield potential of ZZXA12938 was mainly due to the greater number of pods and seeds per plant (Table 2)
Summary
An important raw material in vegetable oil, protein-rich human food, and animal feed, plays an important role in global food security [1,2]. With economic growth and diet change, the demand for soybean products will continue to increase [3,4]. In the case of China, soybean consumption has exceeded 100 million tons in 2017, while the self-sufficiency rate is only approximately 15% [5], a huge supply gap. Many researchers have investigated that planting soybeans densely can remarkably increase aboveground biomass and seed yield [6,7,8,9]. The plots with typical or high yield records often have higher planting densities.
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