Reducing nitrous oxide emissions from a maize‐wheat sequence by decreasing soil nitrate concentration: effects of split application of pig slurry and dicyandiamide

Abstract

Summary Pig slurry ( PS ) is a valuable nitrogen ( N ) source for agricultural crops but the simultaneous supply of readily decomposable carbon and mineral N can result in large soil nitrous oxide ( N 2 O ) emissions. Our objective was to determine the individual and combined effects of split PS application and addition of a nitrification inhibitor (dicyandiamide, DCD ) on N 2 O emissions and soil mineral N concentration in southern B razil. Soil N 2 O fluxes were measured from N ovember 2010 to N ovember 2011 from a maize ( Zea mays L. )‐wheat ( Triticum aestivum L. ) sequence under various fertilizer treatments: no‐ N control, PS applied in a single pre‐plant dose with or without DCD , PS split‐applied with or without DCD , and urea split‐applied. Cumulative N 2 O emissions increased linearly ( R 2 = 0.73) with increasing soil nitrate ( NO 3 − ) exposure, indicating that management practices aimed at reducing soil NO 3 − concentrations can decrease soil N 2 O emissions. In total for the two crops, splitting PS reduced N 2 O emission factors ( EF ) by 33%, whereas the addition of DCD reduced EF by 60 and 41% when PS was applied in single and split doses, respectively. However, splitting PS or adding DCD failed to reduce N 2 O losses more than a single pre‐plant PS application in maize where background soil NO 3 − concentrations were large. The addition of DCD to PS applied as a single pre‐plant dose resulted in the largest reduction in soil N 2 O emissions, whereas splitting PS with and without DCD resulted in significantly smaller abatements. Consequently, we concluded that adding DCD to PS in a single pre‐plant application is a better option than splitting PS applications for reducing soil N 2 O emissions in no‐till cereal cropping systems in southern B razil.