Impacts of Cover Crop Decomposition and Nutrient Release on Agronomic Systems in Southern Illinois.

Midwestern farmers face the challenges of increasing crop production while reducing environmental impacts of nutrient loss from agronomic fields. Best management practices to decrease nutrient and soil loss has fueled the resurgence of the cover cropping practice, but many growers are uncertain about the relationship between cover crop nutrient release and subsequent cash crop uptake in their fields. A litterbag and intact root core study of cover crops was implemented to evaluate hairy vetch (Vicia villosa Roth) and cereal rye (Secale cereale L.) decomposition and nutrient release patterns over a 16 week period, with samples collected at 2, 4, 6, 8, 12, and 16 weeks. Decomposition and nitrogen release data were fit to a single exponential decay model with an asymptote. Cereal rye aboveground (k = 0.1368) and belowground (k = 0.1866) biomass decomposed more gradually compared to hairy vetch aboveground (k = 0.4505) and belowground (k = 0.6821) biomass. The same trend developed for nitrogen release with cereal rye aboveground (k = 0.0703) and belowground (k = 0.1928) biomass releasing nitrogen slower and more gradually compared to hairy vetch aboveground (k = 0.6148) and belowground (k = 0.6052) biomass. Most of the hairy vetch nitrogen was released around Week 2, but the following corn (Zea mays L.) crop did not reach the V6 growth stage until Week 8, therefore cover crop nitrogen release and cash crop uptake may have not been synchronized. This research stresses the importance of cover crop species selection, cover crop termination, and cash crop planting in order to increase the likelihood of crop synchrony.