Resuscitate Soil Health: Cover Crops and Nitrogen Management in Michigan Corn Production.

Plants, soils, and microbes interact to influence plant productivity. Cover crops may provide opportunities to manipulate the soil microbiome but when combined with nitrogen (N) management the impact on soil health and corn (Zea mays L.) production remains ambiguous. Field studies were conducted in 2014 and 2015 to investigate the effects of cover crops and N management strategies on soil bacterial community diversity and corn grain yield. The study was arranged in a split-plot randomized complete block design with four replications. Main plots consisted of cover crop treatments preceding corn and included daikon radish 11.2 kg ha^-1 (Raphanus sativus var. Buster), forage oats 28.0 kg ha^-1 (Avena sativa var. Magnum), and no cover crop. Sub-plot treatments consisted of 179 kg N ha^-1 applied across six different management strategies: urea pre-plant incorporated (PPI), poultry litter PPI plus sidedress N V11, starter N applied 5 cm beside and 5 cm below the furrow followed by sidedress at V4, V11, or V4 plus V11, and a zero N control. Soil data included 16S rRNA sequencing, CO₂ respiration, labile amino-N, and nutrient monitoring. Plant data included cover tissue N and carbon (C), plant height, NDVI, SPAD, R1 tissue sampling, and grain yield. Prior to a November termination, radish and oat covers sequestered 189 and 121 kg N ha^-1 which reduced soil NO₃^- 78 and 84%, respectively, relative to the no cover (fallow) control, increased CO2 respiration 43 and 29%, and increased soil labile amino-N 4.4 and 11.8%. After corn planting, radish and oat covers receiving zero N reduced June soil NO₃^- 13.5 and 27.5%, respectively, from a no cover + zero N which correlated (R²=0.54) to a 1.5 and 1.9 Mg ha^-1 grain yield reduction. Soil microbial DNA results will be presented and discussed.