Nitrification inhibitors reduce nitrogen losses and improve soil health in a subtropical pastureland

Nitrogen (N) fertilizer management in agricultural field affects soil N budget that can have significant implication in greenhouse gas emission and environmental pollution. This study investigates the effects of nitrification inhibitors Dicyandiamide (DCD) and 3,4-dimethyl pyrazole phosphate (DMPP) with urea application on soil N budget and microbial community in a subtropical pasture field. A field experiment consisting of four treatments, including control, urea, urea DCD, and urea DMPP was conducted in 2016 and 2017. Nitrous oxide emission and inorganic-N losses through leaching and runoff were quantified. In addition, soil microbial community response to the imposed treatments was characterized by analysis of phospholipid fatty acid (PLFA). The results showed that DCD and DMPP applications significantly reduced fertilizer-induced N2O emission by over 76% and 67%, respectively. Although nitrification inhibitors' (NIs) applications greatly reduced NO3- in runoff and leaching, there was no significant impact of either NI on pasture biomass yields. Comparing to the plant N uptake, N loss through N2O emission, runoff, and leaching were small in pasture. The low N losses would indicate that NI's potential to increase yield is small. Addition of 10 kg DCD ha(-1) and 1 kg DMPP ha( )(-1)reduced the negative effect induced by urea on total microbial PLFA, and benefited fungi, bacteria, and actinomycetes in short-term. Overall, the results demonstrate the positive effects of NIs on greenhouse gas reduction, water quality, and improving soil health through enhancing total microbial activity and reducing microbial environmental stress.