Improvement of Soybean Resilience to Drought through Deep Root System in Brazil

Water deficit is the major source of yield gap for soybean [ Glycine max (L.) Merr.] in Brazil, which can be mitigated through physiological soybean traits or soil crop management. Considering these two aspects, the aim of this study was to evaluate the soybean yield gain associated with deeper roots, based on different root profiles observed along soybean production areas in Brazil. The effect of root depth was evaluated for 55 growing seasons in 24 locations in the country. The soybean yield simulations were performed with the CSM-CROPGRO-Soybean crop model calibrated for Brazilian conditions. The model's soil root growth factor was changed to create five root distribution profiles in the soil. The deepest root system reached 200 cm, while the shallowest root system was limited to 60 cm. The interaction between root system distribution and climate resulted in different soybean yield levels in the assessed locations. Soybean yield gain increased gradually from shallower to the deeper root systems, ranging between 500 and 2500 kg ha(-1). The yield gain tended to be lower when yield was higher (wet growing season) and higher when yield was lower (dry growing season). Under higher water deficit, the yield gain was reduced for all root systems. The results of this study proved that a better root profi le distribution increases average soybean yield and reduces yield inter-annual variability, mainly where water deficit is a problem. Root profile distribution should be considered for improving soybean resilience to water deficit and adapt the crop for a changing climate.