Comparison of the effectiveness of a nitrification inhibitor, dicyandiamide, in reducing nitrous oxide emissions in four different soils under different climatic and management conditions

Nitrous oxide (N2O) is a potent greenhouse gas and, in New Zealand, about one-third of the total greenhouse gas emissions from the agricultural sector are of N2O, mostly derived from animal excreta in grazed pasture soils. The aim of this study was to determine the effectiveness of a nitrification inhibitor, dicyandiamide (DCD), in reducing N2O emissions from animal urine patches in four different soils located in different regions of New Zealand with different soil, climatic and management conditions. The four soils are Templeton fine sandy loam and Lismore stony silt loam in Canterbury in the South Island, Horotiu silt loam in the Waikato region and Taupo pumice sand near Lake Taupo, both in the North Island. Results showed that the application of a fine-particle suspension nitrification inhibitor, DCD, to grazed pasture soils was very effective in reducing N2O emissions in all four different soils. Total NO emissions (over 69-137 days) from animal urine patches ranged from 1 to 20.9 kg N2O-N ha(-1) without DCD. These were reduced to 0.31-5.7 kg N2O-N ha(-1) by the use of DCD, representing 61-73% reductions (with an average of 70% reduction). The N2O-N emission factor from animal urine N, EF3, was reduced from an average of 0.9 to 0.3% by the use of DCD. These results demonstrate the potential of using nitrification inhibitors to mitigate N2O emissions in a wide range of grazed pasture soils under different climatic and management conditions.