Corn yield response to starter nitrogen rates following a cereal rye cover crop

Cereal rye (Secale cereale L.; CR) is promoted as a cover crop as a practice for reducing nitrate leaching losses in the U.S. Midwest. However, early-season nitrogen immobilization during CR decomposition may contribute to yield reductions in corn (Zea mays L.). Field trials were conducted at three sites to determine if N as a starter fertilizer could increase the plant N uptake and grain yield of corn following CR. Treatments were a two-way factorial with two cover crop treatments (CR and no CR) and four fertilizer treatments: subsurface banded (2 by 2 inches) at planting as urea ammonium nitrate (UAN) at 0, 25, 50, and 75 lb acre^–1. Treatments received the same total N within sites, with the remainder injected between rows at side-dressing as UAN. Nitrogen uptake and yield were unaffected by the starter N × CR interaction in all sites. At one of the sites, CR significantly reduced N uptake and corn yield at the R6 stage by 16 and 4.5% relative to no CR, respectively. Corn yield was unaffected by starter N at two sites, whereas applying 50 or 75 N lb acre^–1 increased yields compared with 0 and 25 N lb acre^–1 at the third site. These findings suggest that starter N could increase early-season N uptake but had an inconsistent impact on corn yields. Therefore, further investigations under different soil N conditions are needed to provide insights into how starter N rates can be adjusted to optimize corn yields within a CR system.