Global Maize Project in the United States: Ames, Iowa

The Ames, Iowa research site is one of several around the world involved in the Global Maize Project. There are several focus areas of the project, including the effect of withholding N application on crop productivity and attempting to increase crop productivity while lessening environmental effects. For the project to date, there are several overall system observations and differences.

One main result is the considerably lower corn yield when no N is applied, in both systems. However, corn yield in the farmer practice where the soil is tilled (tillage for both crops) has higher yield (with no N) than the ecological intensification (EI) system (with no N) where there is strip-tillage (for corn) and no-tillage (for soybean). This indicates probable greater soil N mineralization when the soil is tilled. A second main result has been lower corn yield in the EI system (with N application) compared to the farmer practice. The lower corn yield is attributed to several factors including: the split-N application, lower N fertilizer rate input in the first two years, reduced soil tillage, recent implementation of strip-till and no-till, and post-emergence weed control. The yield difference occurred despite increase in other production practices in the EI system such as higher plant population and addition of S fertilizer. For the selected hybrids, location, and years, the higher plant population may not be positive for increased grain production. The lower yield in the EI system occurred despite improved management with the split N application (compared to an all pre-plant in the farmer practice). However, the farmer practice used anhydrous ammonia, which could partially explain the difference. A third main result is the slower corn growth in the spring and early summer in the EI system, which could be a result of the strip-tillage and resultant cooler soil temperatures, but also could be due to broadcasting the partial N application at planting and at a rate not high enough for full early season growth in the strip-till system. The canopy sensing reference in the EI system has all of the N broadcast applied pre-plant, which has resulted in greater early season growth than in the EI treatment plots. A fourth main result is the similar soybean yield in the two systems, despite the no-till versus tillage in the two systems.

In summary, the farmer practice system has produced higher corn productivity than the EI system, and therefore overall greater crop productivity across the rotation. It is important to realize that good farmer practice in Iowa is highly productive and is near yield potential.