Alleviating the Continuous Corn Yield Penalty with Crop Management.

It is widely accepted that substantial yield reductions occur when corn (Zea mays L.) is continuously grown compared to when it is rotated with soybean [Glycine max (L.) Merr.]; primarily due to nitrogen availability, residue accumulation, and weather. As a result, there is a need to determine how to overcome these causative factors of the continuous corn yield penalty (CCYP) to obtain increased corn yields. Field experiments conducted during 2014 at Urbana, Illinois assessed the yield penalty associated with 11^th year continuous corn vs long-term corn following soybean grown in either a standard or an intensive management system, with contrasting plant populations. The standard management system consisted of a base rate of nitrogen fertilizer, no additional fertility, and no fungicide application. The intensive management system consisted of additional sidedressed nitrogen fertilizer, broadcast and banded fertility, and a foliar fungicide application. Two levels of plant population (79,000 vs 111,000 plants ha^-1) were applied across management systems and eight commercially-available hybrids that had distinctly different genetic makeups were evaluated. Across all treatments, the CCYP was 1.8 Mg ha^-1 (-15%). With standard management, continuous corn yielded significantly less grain than corn following soybean (-2.4 Mg ha^-1). Intensive agronomic management significantly improved grain yield across rotations (2.6 Mg ha^-1), through increased kernel number and kernel weight. There was a 60% greater yield response to intensive management in continuous corn vs the corn-soybean rotation suggesting intensified management as a method to mitigate the CCYP (3.1 Mg ha^-1 increase with intensive management in continuous corn vs a 2.0 Mg ha^-1 increase with rotated corn). With select hybrids, intensive management reduced the CCYP by 60 to 80%. Agronomic management, planting population, and hybrid selection helped alleviate the CCYP demonstrating continuous corn can be managed for better productivity.