Effects of urease and nitrification inhibitors on the soil mineral nitrogen dynamics and nitrous oxide (NO) emissions on calcareous soil.

Urease inhibitors and nitrification inhibitors can reduce nitrogen (N) loss in agriculture soil. However, the effect of inhibitors on soil NO emissions under the drip irrigation system remains unclear. A pot and a field experiment with two inhibitors were conducted to explore how inhibitors regulate soil nitrogen transformation and NO emissions. In the pot experiment, three treatments included control, urea, and urea + N-(n-butyl)thiophosphoric triamide (NBPT, urease inhibitor). In the field experiment, three treatments included control, urea, and urea + NBPT + 2-chloro-6-(trichloromethyl)pyridine (nitrapyrin, nitrification inhibitor). The urease inhibition rate in the treatment of urea + NBPT was 27.5% at the 14th day of incubation (pot experiment), and NH-N was significantly decreased by 37-64% compared with urea alone treatment. In the field experiment, the nitrification inhibition rate in the treatment of urea + NBPT + nitrapyrin was 47.7 and 63.9% on the 3rd day after fertilization at the wheat heading and filling stages, respectively. Compared to urea treatment, NO-N concentration in the double-inhibitor-added treatment was significantly decreased by 32 and 20% on the 5th day after fertilization at the heading and filling stages, respectively; NO fluxes were also decreased by 30.9 and 33.3% at the two stages of wheat, respectively. In total, adding an inhibitor reduced N loss by 7.39 and 7.44% at the 14th and 35th day in the pot experiment and by 10.53 and 6.65% at the two growing stages of wheat in the field experiment, respectively. Path and correlation analysis showed that NO emissions were significantly correlated with soil NO in both pot and field experiments.