Winter Cover Crops Impact on Corn Production in Semiarid Regions

Winter cover crops have produced mixed impacts on crop yields in frigid semiarid environments. Our objective was to determine the influence of winter cover crops and landscape positions on corn (Zea mays L.) yield losses due to water and N stress, soil biology, and gene expression. Following wheat (Triticum aestivum L.), cover crop mixtures were drill seeded into three no-till fields. In the following spring, four N fertilizer rates were applied and corn was no-till seeded. The cover crop had fundamentally different impacts on corn yields at Trail City and Andover in 2011. Both sites were water stressed and responded to N fertilizer; however, at Andover 2011 the cover crop reduced corn yields, while at Trail City 2011 the cover crop did not impact yields. The yield reduction at Andover 2011 was attributed to high cover crop production (>2000 kg ha(-1)), which reduced soil water 15% in the 30- to 60-cm soil depth in November 2010, and in the following growing season increased corn yield loss due to water stress from 1610 to 2950 kg grain ha(-1). Associated with the yield reduction was down expression of two mineral nutrient genes (NCBI, AF325723.1 and APO05869.3) and one gene associated with energy processing (AF325723.1). The cover crops reduced the relative amount of soil NO3 at four of the six landscape positions and increased the relative bacteria/fungi ratio in 2011. These findings indicate that cover crops after winter wheat can be an important mechanism for scavenging N in semiarid frigid environments; however, adopting techniques that generate high cover crop yields can adversely influence the following cash crop.