Greenhouse Gas Emissions with Low Disturbance Liquid Dairy Manure Incorporation into a Live Winter Cereal Cover Crop-Corn System

Dairy manure is an important nutrient source for crops but can also contribute to ammonia (NH3) and greenhouse gas (GHG) emissions. While incorporating manure into the soil reduces nutrient loss potential in surface runoff, impacts on GHGs are unclear. Here, our objective was to quantify NH3, nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2) fluxes for two seasons after liquid dairy manure was spring-applied to a live winter cereal cover crop-corn system with different incorporation methods. Broadcast application and no manure controls were compared to manure incorporated by vertical tillage (VT) or chisel plowing (CP). Corn yields did not differ in 2018 but were greater for CP in 2019. Mean NH3 emissions for VT were 70 and 23% of broadcast and 7 and 11% of broadcast for CP in 2018 and 2019, respectively. While VT N2O-N fluxes were also about 70% lower than broadcast both years, CO2 fluxes were larger for VT. On average, CP and VT had 16 and 4% lower global warming potential (GWP) index values than broadcast, respectively. Despite differing effects on N2O, our results showed that CP more effectively conserved NH3 while reducing GWP from liquid manure compared to VT, stressing the importance of site-specific soil-manure-tillage interactions when quantifying dairy system GHG fluxes.