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

In 2012, we established our first field experiments in this international research effort at Purdue’s Agronomy Center for Research and Education (West Lafayette, IN). Like other ongoing studies, our research involved a comparison of traditional farmer practices (FP) versus ecological intensification (EI) practices for rain-fed maize in a conventional maize-soybean rotation. Unlike most other studies, we elected to employ fall strip-till, three management levels, and six replications in each practice. The FP plots involve a normal plant density (~31,000 plants/A), at sidedress N application rates of 0, 100 and 160 lb of N/A following starter fertilizer application of ~20 lb N/A at planting. The EI plots used the same drought-tolerant hybrid (Pioneer 1498) at a higher plant density (~38,000 plants/A), at sidedress N rates of 0, 160 and 220 lb N/A, but with the addition of a nitrification inhibitor (Instinct™) and ammonium sulfate (Thiosulfate) to the banded UAN. Since our overall goals are to increase maize yields and improve nutrient use efficiencies simultaneously, we closely monitor plant nutrient uptake at flowering and maturity.

Maize yields were highly responsive to N application rates, but not to the higher plant density, in all three years. Average maize yields with optimum N rates only reached a high of 157 bu/A in the drought year of 2012, versus highs of 240 and 243 bu/A in 2013 and 2014. Because the zero N treatment averaged just 110 bu/A in those two years, we had high N use efficiency (NUE). In the 160 lb of N/A EI treatment, NUE averaged 47 and 48 lb grain per lb N fertilizer, respectively in 2013 and 2014. Fertilizer N recovery efficiency (NRE) in the whole-plant biomass at maturity in 2013 reached 80% at the 100 N rate, and was up to 70% at the 160 N rate. However, although NUE was higher with EI, NRE was highest with FP. Maize ear-leaf N concentrations at flowering (2012 to 2014) were highest with the 220 N EI treatment. Plant N concentrations from the 2014 harvest, plus other relevant macro- and micro-nutrient concentrations from all years, are being analyzed.

Future plans include switching to maize hybrids with a higher yield potential and investigating other ways of improving the “ecological” aspects of the EI system. In particular, we are examining nutrient placement strategies that may provide better nutrition in reduced tillage systems. We look forward to achieving further gains in nutrient efficiencies in the EI system.