Advancing Intensive Management of Corn Systems in Minnesota (Irrigated)

In 2014, an experiment was established on an irrigated loamy sand Mollisol in central Minnesota near Becker. Maize was produced continuously. Sulfur (S) was applied pre-plant at 17 kg S/ha, and a solution of nitrogen (5 kg N/ha) and phosphorus (18 kg P₂O₅/ha) was applied in-furrow during planting. The experiment compared farmer practice (FP) and ecological intensification (EI) management systems, developed in consultation with researchers, crop advisers, and farmers. Compared to the FP system, EI had 40% of maize stover harvested after grain harvest and before fall tillage, in combination with a longer-season hybrid and a 14% greater planting density (101,000 seeds/ha).

Two nutrient management approaches (standard and advanced) were evaluated within both the EI and FP systems. The coarse-textured soil warranted in-season split application of N with both nutrient management approaches. Standard nutrient management followed university guidelines, using sidedressed applications of urea at early (two and six leaf-collar) maize stages (45 and 185 kg N/ha, respectively). Advanced nutrient management applied P and potassium (K) at rates equivalent to removal by grain. It also used 27 kg N/ha in a band on the surface 5 cm to the side of the row at planting, using a solution of ammonium thiosulfate and urea ammonium nitrate. Subsequent urea applications were made at the six leaf-collar, twelve leaf-collar, and tasseling maize stages at 78, 85, and 39 kg N/ha, respectively.

In this region with a long history of intensive maize production and high yields, substantial yield increases were still possible with improved agronomic and nutrient management practices. Advanced nutrient management combined with the EI management system (EI/advanced) produced greatest maize grain yield; however, the standard nutrient approach combined with the EI system (EI/standard) produced the greatest improvement in economic net return. The EI/standard combination improved net economic return in all 3 years. It also had the second-greatest agronomic efficiency of N and recovery efficiency of N.

Results from this study demonstrate the potential for improvement in corn yield and N use efficiency in environments where customary practices produce high grain yield (>9 t dry matter/ha). Weather and crop responses are dynamic over time. Additional years of research will provide greater understanding of where, when, and to what extent advanced nutrient and agronomic management approaches can narrow yield gaps while limiting economic risk and enhancing environmental stewardship.