Cropland soil nitrogen oxide emissions vary with dairy manure incorporation methods

Abstract

AbstractSoils contribute 15%–75% of total atmospheric nitrogen oxide (NOx) emissions in agricultural regions during the growing season. However, the impacts of cropland fertilizer management on spatially heterogeneous, temporally episodic NOx emission patterns are highly uncertain. We examine the effects of liquid slurry dairy manure application practices on soil NOx emissions in rainfed, corn‐soybean rotations during spring 2016 and 2017. Daily soil NOx emissions and weekly soil inorganic N measurements were performed in a randomized split–split plot design for 1–4 weeks following manure applications. NOx emissions and soil N with shallow‐disk injection and chisel‐disk manure incorporation methods were compared with unincorporated broadcast practices. Injected manure and chisel‐disk incorporation exhibited two–four times larger mean NOx emissions than those with unincorporated broadcast manure. Larger soil NOx emissions with manure incorporation practices were driven by the predominance of nitrification in these treatments with evidence of soil nitrate production. Soil NOx emission differences between treatments were detectable across order of magnitude changes in daily NOx emissions during two growing seasons. Larger soil NOx emissions associated with manure incorporation practices compared with unincorporated broadcast practices occur alongside larger N2O and smaller NH3 emissions, highlighting important air quality and climate impact tradeoffs for cropland manure fertilizer management choices.