Cropland soil nitrogen oxide emissions vary with dairy manure incorporation methods

Authors: MILLER, DAVID - Brown University; CHAI, JIAJUE - Brown University; GAO, FELIX - Brown University; PONCE DE LEON, MARIA - Pennsylvania State University; RYALS, REBECCA - University Of California; Dell, Curtis; KARSTEN, HEATHER - Pennsylvania State University; HASTINGS, MEREDITH - Brown University

Submitted to: Agrosystems, Geosciences & Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/31/2024
Publication Date: 4/29/2024
Citation: Miller, D., Chai, J., Gao, F., Ponce De Leon, M.A., Ryals, R., Dell, C.J., Karsten, H., Hastings, M. 2024. Cropland soil nitrogen oxide emissions vary with dairy manure incorporation methods. Agrosystems, Geosciences & Environment. 7(2):e20485.
DOI: https://doi.org/10.1002/agg2.20485

Interpretive Summary: Nitrogen oxides (NOx) are emitted from soils in response to manure and fertilizer application, and they contribute to smog formation, acid rain, and depletion of ozone in the atmosphere. Studies were conducted in central Pennsylvania to determine how injection of dairy manure into no-till corn fields, which has been previously shown to greatly reduce loss of nitrogen as ammonia, impacted NOx emissions. The study showed that NOx emission was increased by about 23% with injection (compared to leaving the manure on the soil surface), which offsets some of the benefit of reduced ammonia emissions.

Technical Abstract: Soil emissions represent up to ~40% of agricultural season atmospheric nitrogen oxide (NOx) emissions. The impacts of agricultural field management practices on heterogeneous, episodic soil reactive N emission budgets are highly uncertain. We examine the influence of dairy manure-fertilized cropland management practices on soil NOx emissions and their contributions to total reactive N (NOx, nitrous oxide, ammonia) budgets in central Pennsylvania, USA. Rainfed, corn-soybean rotation plots were sampled daily following dairy manure applications with shallow-disc injection, broadcast chisel-disc and broadcast no-till during two spring and one fall growing seasons. Injected manure and broadcast chisel-disc exhibited two to four times greater mean NOx emissions than those for broadcast no-till. These differences depend on soil moisture and ammonium availability. Currently, soils are the third largest NOx source (10-15% of emissions budget) in central PA during the growing season. The adoption of manure injection on 20-50% current cropland with broadcast manure no-till decreases total reactive N emissions by a factor of 6 due to ammonia emission reductions but increases NOx and nitrous oxide emissions by > 23% and >51%, respectively. Our results highlight tradeoffs among various field management choices for air quality, N deposition, and climate change impacts.