Effects of Solid Dairy Manure Application on Greenhouse Gas Emissions and Corn Yield in the Upper Midwest, USA

Dairy manure is an important nitrogen (N) source for crops, but its role in greenhouse gas (GHG) emissions and farm sustainability is not fully understood. We evaluated the effects of application of two dairy manure sources (bedded pack heifer, BP, and separated dairy solids, SDS) on corn silage yield and GHG emissions (carbon dioxide, CO2; methane, CH4; nitrous oxide, N2O) compared to a urea-fertilizer-only control (80 kg N ha−1 yr−1). The BP and SDS were applied at 18.4 and 19.4 Mg dry matter ha−1 in fall 2020 in the final year of ryegrass production. No-till corn was planted from 2021 to 2023, and GHG emissions were measured each season (from May to November). The results showed significantly greater CO2-C emissions for BP in 2021 and no differences in 2022 or 2023. A small N2O-N emission increase for BP occurred in the spring after application; however, seasonal fluxes were low or negative. Mean CH4-C emissions ranged from 2 to 7 kg ha−1 yr−1 with no treatment differences. Lack of soil aeration appeared to be an important factor affecting seasonal N2O-N and CH4-C emissions. The results suggest that GHG models should account for field-level nutrient management factors in addition to soil aeration status.