High-yield maize-soybean cropping systems in the US Corn Belt

The USA accounts for 38 and 35% of global maize and soybean production, producing a respective 320 and 84 Mt of these crops annually. More than 85% of those totals are produced in the north-central region known as the 'Corn Belt', where continuous maize and 2-year maize-soybean rotation are the dominant cropping systems. This chapter describes the climate, soil, and management practices of high-yield maize-soybean cropping systems in the Corn Belt. Major drivers for higher yields and resource-use efficiency are evaluated and opportunities for further improvement are discussed. Yield and input-use efficiency of maize and soybean in the US Corn Belt have increased steadily during the last 40 years as a result of (1) continuous genetic improvement, (2) intermittently phased periods of agronomic improvement, and (3) the synergistic interaction of improved genetics and agronomy. Future increases may be difficult to achieve as on-farm yields approach yield potential; however, some of the yield gap between on-farm yield and simulated yield potential can still be captured by fine-tuning crop management in a manner that increases yield, while simultaneously reducing the resource input amount or cost. Indeed, substantive opportunities exist for increased input-use efficiency by scheduling just-in-time irrigation events of the minimum amount needed, and by optimizing management of N fertilizer to be temporally and spatially effective.