Advancing Intensive Management of Corn Systems in Minnesota (Rainfed)

In 2013, an experiment was established on a rain-fed, tile-drained clay loam Mollisol in south-central Minnesota, USA, near Waseca. Maize was produced continuously, and a disk-rip tillage system was used. 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. Standard nutrient management followed university guidelines, applying 180 kg N/ha pre-plant as urea. The advanced nutrient management treatment applied P and K equivalent to rates of removal by grain and also utilized a split-application of N. Urea was applied pre-plant at 152 kg N/ha. At planting, a solution of ammonium thiosulfate and urea ammonium nitrate was applied in a band placed on the surface 5 cm to the side of the row at 27 kg N/ha. The final 45 kg N/ha was sidedressed at the six leaf-collar maize stage as UAN injected midway between the 76-cm rows.

In a region with a long history of intensive maize production and high yields, substantial yield increases were possible with improved agronomic and nutrient management practices. Advanced nutrient management combined with the EI management system (EI/advanced) produced the 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 return in 3 of 4 years. It also had the greatest agronomic efficiency of N and the greatest recovery efficiency of N.

Results from this study demonstrate 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.