On-Farm Nitrification Inhibitor Application to Urine Patches in Reducing Nitrous Oxide Emissions

In livestock-grazed pastures, urine patches are a major contributor of nitrous oxide (N2O) emissions, and the use of nitrification inhibitors (NIs) has the potential to reduce N losses from urine patches using New Zealand (NZ)-devised Spikey®—a ground-based machine that measures the change in soil conductivity from the deposited urine patches. Our ongoing research suggests that the efficacy of on-farm targeted NIs treatment requires suitable inhibitor concentrations within urine patches to be achieved to reduce N2O emissions. This study evaluates the effect of varying NI rates and volumes on reducing N2O emissions. The application rates for NIs were 1.6 g and 3.2 g dicyanamide (DCD) patch-1 and 0.96 g and 1.92 g of 3, 4-dimethylpyrazole phosphate (DMPP) patch−1, using 100, 150, and 200 mL inhibitor solutions. These rates were higher than those used in previous studies to ensure an adequate supply of inhibitors above the threshold concentration within the urine patch and to enhance the inhibitor efficacy in reducing N2O emissions. This study points to two important aspects: Determine the optimum inhibitor concentration required to eliminate, minimise/reduce N2O emissions and ensure that at the optimised amounts of inhibitor application rates, inhibitor residues are below their maximum residue level (MRL) in the food chain and environment, and eliminate their potential harm to human health.