Split fertilizer nitrogen application with a cereal rye cover crop reduces tile nitrate loads in a corn-soybean rotation.

Split applications of fertilizer nitrogen (N) and cover crops are management strategies employed to reduce nitrate in tile drainage water while maintaining crop yields. Our aim was to investigate split fertilizer N applications to corn (Zea mays L.) on crop yields and tile nitrate loss in a corn-soybean (Glycine max L.) rotation from 2016 through 2019. In addition, we evaluated the inclusion of cover crops on crop yields and tile nitrate loss. Thirty-six tile-drained plots were used to accommodate six fertilizer N treatments, three replicates, and both phases of the rotation. Fertilizer N treatments were as follows: 100% in the fall; 50% in the fall, 25% at planting, and 25% at side-dress; 100% in the spring preplant; 75% in the spring preplant; 50% in the spring preplant and 50% at side-dress; and 50% in the spring preplant and 50% at side-dress with a cover crop. We did not find significant differences between split N application treatments and their single application companion treatments for corn yield or tile nitrate loss; however, the reduced fertilizer N rate treatment significantly decreased corn yields. Cumulative tile nitrate losses ranged from 115 kg ha < sup > -1 < /sup > for 100% in the fall to 65 kg ha < sup > -1 < /sup > for 50% in the spring preplant and 50% at side-dress with a cover crop, representing a tile nitrate reduction of 43%. Overall, this research demonstrated tile nitrate loads in a corn-soybean rotation are controlled by the interaction of weather patterns (temperature and precipitation), timing and rate of fertilizer N, and previous crop. This article is protected by copyright. All rights reserved.