Impact of Cover Crop Species on Enzyme Activity and Nitrogen Supply at Corn Growth Stages.

Though the soil microbial community plays an important role in plant productivity and ecosystem functioning, there is a lack of knowledge surrounding the impact of cover crop addition to monocropped agroecosystems on the soil microbial community dynamics and biogeochemical cycling. Therefore, the objectives of this study are to i) determine the impact of cover crop species and residue management on the release of nitrogen (N) following cover crop termination and, ii) analyze the short-term dynamics of soil N and carbon cycling enzymes at corn growth stages during the course of the corn (Zea mays) growing season. Cover crop treatments in this study included hairy vetch (Vicia villosa Roth), cereal rye (Secale cereal), a hairy vetch/cereal rye mixture, and a no cover crop control, preceding the corn cash crop. Results from the 2016 corn growing season indicate that β-glucosidase activity in all cover crop litter treatments decreased over the growing season, while urease activity in the cereal rye litter peaked, and was significantly greater, in early August when the maize was entering its second reproductive stage (R2) (p<0.05). Soil β-glucosidase activity in early June, when the maize crop had developed six visible leaves (V6), was significantly greater for cereal rye dominated treatments relative to hairy vetch treatments, but was similar to the control (p<0.05). This soil β-glucosidase peak preceded that of the plant available N in late June when the maize had developed tassels (VT). Results from the 2017 growing season indicate that litter and soil enzyme activity are undergoing similar trends compared to 2016, but increased precipitation during the 2017 corn-growing season has influenced enzyme activity and inorganic N supply. Data generated from this study will lead to a deeper understanding of growing season N dynamics in cover cropped corn agroecosystems that could lead to decreased synthetic fertilizer dependence.