Diethyl aminoethyl hexanoate (DA-6) and planting density optimize soybean growth and yield formation in maize–soybean strip intercropping
Kai Luo, Xiaoting Yuan, Kejing Zhang, Yuanyuan Xue, Zhidan Fu, Ping Lin, Yiling Li, Yüze Li, Pu Tian, Xiaolong Qi, Yang Li, Xiaochun Wang, Wenyu Yang, Jaume Flexas, Taiwen Yong
Abstract
The exogenous plant growth regulator, diethyl aminoethyl hexanoate (DA-6), in combination with suitable varieties and planting densities, is important to increase yield in the maize soybean strip intercropping system. To identify the role of DA-6 in mitigating high-density stress and increasing yield, we conducted a two-year field experiment examining changes in branching architecture and other yield traits of soybeans in maize–soybean strip intercropping systems. In the planting system, two soybean cultivars (ND: Nandou 25 and QH: Qihuang 34) were grown under three planting densities (D1: 102,000 plants ha −1 , D2: 130,000 plants ha −1 , D3: 158,000 plants ha −1 ) with DA-6 treatments (DA0: water control; DA60: 60 mg L −1 ; DA100: 100 mg L −1 ). Applying DA-6 at 60 mg L −1 at the fourth trifoliolate leaf stage increased soybean yield, with QH yield rising by 22.4 % and 29.5 % at D3 density, and ND yield by 29.5 % and 30.0 % at D2 density in 2022 and 2023, respectively, compared with D1 under DA0. DA-6 improved photosynthesis in both varieties under D2 density, with DA60 increasing ND canopy photosynthetic rate by 15.1–16.4 % and QG by 9.1 %–20.6 % over two years. In ND, DA-6 enhanced branching, raising the leaf area index by 37 %, branch number from 3.6 to 4.7 per plant, and total pod number by 19.7 %. In QH, yield grains were mainly due to a 17 % increase in the number of stem pods and a 6.5 % improvement in hundred-grain weight. In the maize soybean strip intercropping system, QH achieved a high yield by forming a high-density (D2 to D3) main stem pod, and ND by combining moderate density (D1 to D2) with DA-6-induced branching.