Enhancing Corn Yield in a Winter Cereal Rye Cover Crop System.

Cereal rye (Secale cereal L.) cover crops (RCC) have good potential to take up residual nitrate and reduce losses. However, studies in Iowa have shown a 5-6% corn (Zea mays L.) yield reduction when grown following a RCC. That reduction is unacceptable to farmers and would discourage cover crop adoption. The objective of this research was to study management practices that have potential to improve corn yield with a RCC. This study was conducted at four sites in Iowa in 2014 and 2015, in a split-split plot randomized complete block design with corn grown in rotation with soybean [Glycine max. (L.) Merr.]. The main plot was rye broadcast into soybean before leaf drop and no rye, the split plot tillage (disk before corn) or no-till, and the split-split plot starter (34 kg N/ha) or no starter. Corn population was determined at the V6 growth stage, corn canopy sensing at the V10 growth stage using a RapidSCAN CS-45 sensor (Holland Scientific), and corn and soybean grain yield. In 2014, corn yield was not affected by the RCC and there were no interactive effects of tillage or starter with RCC. The lack of RCC effect on corn yield was mainly due to poor rye stand from aerial seeding and low springtime biomass production. Corn yield was higher (p<0.10) with starter at one site and with tillage at one site. Soybean yield was higher at one site with tillage, higher with no-till at another site, and no residual effect of the RCC system. In 2014 and 2015, the RCC and tillage system had a small/inconsistent effect at six site-years on corn normalized difference vegetation index (NDVI), and NDVI was greater with starter at four site-years. The RCC had no influence on corn population but no-till had higher population than tillage at five site-years. While the RCC did not affect corn yield (only 2014 data), starter N did increase corn early growth (greater NDVI) and yield at some sites, which might offset any negative impact of a RCC on corn production.