Greenhouse gas emissions with low disturbance liquid dairy manure incorporation into a live winter cereal cover crop-corn system

Authors: Sherman, Jessica; Young, Eric

Submitted to: Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/24/2022
Publication Date: 11/27/2022
Citation: Sherman, J.F., Young, E.O. 2022. Greenhouse gas emissions with low disturbance liquid dairy manure incorporation into a live winter cereal cover crop-corn system. Agronomy. 12(12). Article 2978. https://doi.org/10.3390/agronomy12122978.
DOI: https://doi.org/10.3390/agronomy12122978

Interpretive Summary: Dairy manure can provide a substantial amount of the annual crop nutrient needs on dairy farms, however manure and tillage operations may contribute to ammonia and greenhouse gas emissions. Incorporating manure into the soil using conventional (i.e., chisel plowing, disking) or low-disturbance tools such as vertical tillage reduces nutrient loss potential in runoff, however the impacts of different tillage types on greenhouse gas emissions are not well known. A study was conducted at the Marshfield Agricultural Research Station in 2018 and 2019 to quantify ammonia, nitrous oxide, methane, and carbon dioxide emissions after liquid dairy manure was spring-applied in a live winter cereal cover crop-corn system. Broadcast manure application (applied on the soil surface) and no manure controls were compared to manure incorporated by vertical or chisel plow tillage. Results showed that corn silage yields did not differ in 2018 but were significantly larger for chisel plow in 2019. In both years, ammonia emissions for vertical and chisel plow were much lower than broadcast. While vertical tillage also decreased nitrous oxide emission both years (to near 70% of broadcast), carbon dioxide fluxes were larger than those for chisel plowing. Despite inconsistent effects on nitrous oxide, chisel plowing more effectively conserved ammonia from liquid manure and reduced global warming potential compared to vertical tillage. Results stress the importance of evaluating site-specific interactions when developing greenhouse gas models for dairy systems.

Technical Abstract: Dairy manure is an important nutrient source for crops but can contribute to ammonia (NH3) and greenhouse gas (GHG) emissions. Incorporating manure reduces nutrient loss potential in runoff, however tillage impacts on GHGs are less established. The objective here was to quantify NH3, nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2) fluxes for two seasons after liquid dairy manure was spring-applied in a live winter cereal cover crop-corn system at the Marshfield Agricultural Research Station. 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 also decreased N2O-N emission (to near 70% of broadcast) both years, CO2 fluxes were larger for VT compared to CP. 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 suggest that CP more effectively conserved NH3 from liquid manure and reduced GWP compared to VT, stressing the need to consider site-specific interactions when quantifying GHGs in dairy systems.