Biophysical and management factors causing yield gap in soybean in the subtropics of Brazil

Little is known about the relationships between soybean [Glycine max (L.) Merr.] maturity grouping and the yield-limiting factors in the subtropics. This information can be used to estimate soybean potential yield (Yp) and the water-limited yield (Yw) and to optimize current soybean management practices to improve yield and resource use efficiency. The objectives were (a) to estimate the Yp, Yw, and yield gaps (YGs) of soybean in subtropical Brazil and (b) to identify the biophysical and management factors which potentially explain the YG. The CSM CROPGRO model that was calibrated with data collected between 2011 and 2019 was used to estimate the influence of sowing date and maturity group (MG) on yield potentials and water efficiencies. Yield varied from 6.1 to 7.2 Mg ha(-1) and from 2.5 to 5.1 Mg ha(-1) between buffer zones (BZs) for Yp and Yw, respectively. The YG caused by water deficit (YGw) ranged from 26% (1.8 Mg ha(-1)) to 62% (4.1 Mg ha(-1)) of the Yp and the YG caused by management (e.g., sowing date, MG, final density) ranged from 9% (0.6 Mg ha(-1)) to 39% (2.7 Mg ha(-1)) of the Yp. The main management factor of the YG was sowing date. The potential yield was higher in the early MGs, showing greater water use efficiency in MG <= 5.5 (9.6 kg ha(-1) mm(-1)) than in high MGs (MG >= 5.6). Findings from this study can be used by agronomists in subtropical regions to optimize soybean yields.

Automated summary

In subtropical Brazil, soybean potential yield is affected by sowing date and maturity group, with water deficit and management factors contributing to yield gaps. Early maturity group soybeans in this region show higher potential yield and water use efficiency compared to later maturity groups.