Impoverishing Roots Will Improve Wheat Yield and Profitability Through Increased Water and Nitrogen Use Efficiencies.

More than a 60% increase in crop production is required by the 2050's to feed a growing world population. Understanding how plant functional traits and field management affect crop yields has the potential to improve agricultural productivity, minimize economic and environmental losses, and maximize food security. We explored the influence of winter wheat root characteristics and management on winter wheat growth, yield, and profit using a mechanistic and well‐tested ecosystem and crop model, ecosys. We applied and further tested ecosys at an agricultural farm growing winter wheat in Ardmore, Oklahoma, United States. The model accurately predicted observed shoot carbon (R2 = 0.95), soil moisture (R2 = 0.67), soil temperature (R2 = 0.91), and yield (percent error = 17%). Numerical optimization experiments were conducted to explore potential improvements of winter wheat yield and profit by modifying root characteristics, including root radius and root:shoot carbon transfer conductance, and fertilizer inputs. Our results show the potential for simultaneously improving winter wheat yields and profits. The optimum conditions were found to be in the range of root radius between 0.1 and 0.3 mm, carbon transfer conductance between 0.004 and 0.01 h−1, and the currently applied fertilizer rate of 112 kg ha−1. Under these conditions, improvements in yields and profits of up to approximately 25% and 110%, respectively, were modeled compared to those under baseline root traits. These improvements were achieved by impoverishing root structures, thereby increasing nutrient allocation to grains. Our results also demonstrate and motivate model structures that integrate the complex network of plant physiology, soil nutrient biogeochemistry, hydrology, and management. Plain Language Summary: To meet projected food demands for a growing world population, crop yields need to be doubled by the 2050's. Although aboveground crop traits have been widely studied to improve crop yields, the "invisible" part of the crop, root systems, is not well studied. In this study, we performed a numerical optimization of root traits (such as root radius and carbon transfer conductance between shoot and root) and fertilizer application rate using a well‐tested coupled ecohydrological and biogeochemical model. We found that engineering deeper wheat root structures could improve yields and profits by 25% and 110%, respectively, compared to the present day without additional fertilizer inputs. These improvements were accompanied by almost no change in nitrogen losses via surface N2O fluxes, indicating that the optimized root traits were an environmentally friendly option to meet future food demands. Key Points: Improved water and nitrogen use efficiencies were modeled when optimizing root radius and root:shoot carbon transfer conductanceOptimizing root traits could improve wheat yields and profits without considerable nitrogen losses via nitrate leaching and N2O emissionsThese optimized root traits imply some loss of resilience to environmental stressors, such as drought [ABSTRACT FROM AUTHOR]