Global Maize Project in the United States: Ames, Iowa

This rain-fed site was located on a Mollisol near the city of Ames, Iowa. Maize and soybean were grown in alternate years on the same experimental area over time. The Ecological Intensification (EI) system incorporated several changes compared to the Farmer Practice (FP) system. Strip-till maize and no-till soybean was used in the EI system instead of the more intensive, full-width conventional tillage. During the duration of the experiment (2011 to 2016), the EI treatment had maize seeding rates 19 to 27% greater than the FP. Planting dates were the same for both treatments, except for 2012 when EI was planted 28 days later. Nitrogen (N) application rates for EI were generally lower (14 to 17% lower in four of the experimental years, equivalent in one year and 18% higher in another year). In EI, N was split applied, with ammonium nitrate broadcast pre-plant, followed by side-dressed (V5 maize growth stage) urea ammonium nitrate banded 10 cm below the surface, with bands applied midway between every-other 76 cm maize row. Maize canopy sensing at the V10 maize growth stage was conducted each year to monitor EI treatments. However, only in the third and fourth years of the experiment was there a late-season application of either urea with a urease inhibitor or ammonium nitrate. In the FP, anhydrous ammonia was applied spring pre-plant, in 20-cm deep bands midway between each row. For each system, there was also a treatment with no N application.

Analyzed across 2011 to 2016, the two management systems did not differ in average maize grain yield when fertilized with N; however, maize in the EI system did accumulate a lower quantity of N when fertilized. When no N fertilizer was applied, both grain yield and N uptake in the EI system were lower than those in FP. The EI system had greater N use efficiency - a function of the lower unfertilized yields and lower N application rates in the EI system. These results may point to a reduced ability of the soil in EI to supply N for maize uptake, a greater reliance on applied fertilizer N for optimal yield, and, when no N is applied a greater chance for soil N resource depletion in FP.