Residue and Agronomic Management to Lessen the Continuous Corn Yield Penalty.

Grain yields of continuously grown corn (Zea mays L.) are generally less than when corn is rotated with soybean [Glycine max (L.) Merr.]; primarily due to nitrogen availability, residue accumulation, and weather. The objective of this study was to test if residue management and the level of agronomic inputs could lessen the continuous corn yield penalty (CCYP). Field experiments conducted during 2015-2016 at Urbana, Illinois assessed the yield penalty associated with 13^th year continuous corn vs. long-term corn following soybean grown in either a standard or an intensive management system, both with contrasting mechanical and chemical residue treatments. For the mechanical residue treatments, the previous year’s corn crop was harvested with a combine head equipped with Calmer BT Chopper stalk rollers or with standard knife rollers, and both mechanical treatments were managed chemically with Extract Powered by Accomplish, or with ammonium sulfate (47 kg N ha^-1), and compared to an untreated control. Across rotation and residue blocks, the standard management system was seeded to achieve a final stand of 79,000 plants ha^-1 and received a base rate of nitrogen fertilizer, no additional fertility, and no fungicide application, while the intensive management system was seeded at 111,000 plants ha^-1 and consisted of additional sidedressed nitrogen fertilizer, broadcast and banded fertility, and a foliar fungicide application. Two commercial hybrids previously characterized as tolerant vs. intolerant to continuous corn were evaluated across all treatments. From fall to spring, residue degradation significantly improved with chopped vs. standard residue harvest (residue reduced by 52% vs. 44%). Time to 75% emergence was 11% slower in continuous corn compared to the corn-soybean rotation. Hybrid selection with intensive management reduced the CCYP by 40 to 80%. Throughout the growing season, residue and agronomic management helped lessen inherent yield losses of continuous corn demonstrating the CCYP can be managed.