Dicyandiamide application plus incorporation into soil reduces N2O and NH3 emissions from anaerobically digested cattle slurry

Abstract

Livestock slurry application to land recycles nutrients for plant uptake, but resulting gaseous nitrogen (N) emissions pose a major challenge to the environment. This study was conducted to investigate environmentally friendly methods for the application of anaerobically digested cattle slurry (ADCS) to soil. Application techniques of control (C), surface application (S), incorporation into the soil (I) and soil amendments with and without a nitrification inhibitor (dicyandiamide, DCD) were compared in a small-scale laboratory experiment. Ammonia (NH3) volatilisation mainly occurred within 5 days after ADCS application. Cumulative NH3 volatilisation loss accounted for 57.0, 59.9, 0.7 and 1.4% of applied NH4+-N from surface applied ADCS without and with DCD, and from incorporated ADCS without and with DCD, respectively. Ammonia volatilisation from surface-applied ADCS was 56 times greater than from incorporated ADCS. The nitrous oxide (N2O) emission flux from soil where ADCS was surface-applied without DCD was significantly (P < 0.01) higher than that from the other treatments. The DCD supplement significantly (P < 0.05) reduced N2O flux from surface-applied and incorporated ADCS. Therefore, the cumulative N2O emission loss from the soil where ADCS was surface-applied was significantly greater than that from the incorporated slurry regardless of the DCD supplement. Total inorganic N (TIN) in the soil for all treatments remained constant, although NH4+-N contents in the soil without DCD decreased continuously and nitrate nitrogen (NO3–-N) contents increased continuously throughout trials. There were significant (P < 0.01) differences in TIN contents among application techniques. NH3 volatilisation from the surface application was a major cause of the differences. Consequently, the incorporation of ADCS with the DCD supplement could be a potential method to successfully reduce emissions of both NH3 and N2O.