Global Maize Project in the United States: West Lafayette, Indiana

We established our first field experiments in this international effort at Purdue’s Agronomy Center for Research and Education (West Lafayette, IN) in 2012. Like other ongoing studies, our research involved a comparison of traditional farmer practices (FP) versus ecological intensification (EI) practices for rainfed maize in a conventional maize-soybean rotation. Unlike other studies, we employed fall strip-till, three management levels, and six replications. The FP plots involve a normal plant density (~31,000 plants/A), at sidedress N application rates of 0, 100, and 160 lb N/A following starter fertilizer application of ~20 lb N/A at planting. The EI plots used the same hybrid (P1498 from 2012 to 2014, and P1417AMX in 2015), but at a higher plant density (~38,000 plants/A), with sidedress N rates of 0, 160, and 220 lb N/A plus an inhibitor (Instinct™) and ammonium sulfate (Thiosulfate) in the banded UAN. In 2015, we also added broadcast Aspire® (potash/boron) to the EI plots.

Maize yields were highly responsive to N application rates in all four years, but to plant density only in 2015. Average maize yields with optimum N rates reached a high of only 157 bu/A in the drought year of 2012, versus highs of 240, 243, and 212 bu/A in 2013, 2014 and 2015, respectively. We had our biggest yield response to the EI treatments in 2015, when grain yields with EI averaged 42 bu/A higher at 220 N, and 17 bu/A higher at 160 N, relative to 160 lb N/A rate with FP. Because the zero N treatment yielded only 102 bu/A (FP) and 94 bu/A (EI) in the four years, we had high N use efficiency (NUE). With the 160 lb N/A rate for the EI treatment, NUE averaged 68 lb grain/lb N fertilizer across four years. Fertilizer N recovery efficiency (NRE) by whole-plant biomass at maturity averaged 60 % with the 160 N rate for the EI treatment from 2012-2015. Total plant nutrient uptake for N, P, K, S, Zn, Cu, and B was significantly higher with the 220 N rate for the EI treatment than for other treatments.

With additional 4R Nutrient Stewardship Funding in 2015, we were able to add intensive greenhouse gas sampling measurements during the growing season. Because of excessive rain in June, 2015, we had high N₂O losses in the 0 N control treatments but no higher losses in EI than FP. We look forward to achieving further gains in nutrient efficiencies in the EI system.