A 2-yr field assessment of the effects of chemical and biological nitrification inhibitors on nitrous oxide emissions and nitrogen use efficiency in an intensively managed vegetable cropping system

The application of nitrification inhibitors (NIs) is effective in suppressing nitrification and N2O emissions while promoting crop yields in many agroecosystems. However, the inhibitory effects of different NIs for vegetable production under soil and environmental conditions in China are not fully understood. To evaluate the effects of chemical and biological NIs on N2O emissions and the nitrogen use efficiency (NUE), a 2-yr field experiment with four treatments (regular urea (Urea), urea + dicyandiamide (DCD), urea + nitrapyrin (CP) and urea + biological nitrification inhibitor (BNI)) performed in triplicate was carried out in an intensive vegetable field using the static chamber and gas chromatography method. The results showed that the CP and BNI treatments shifted the main form of soil inorganic nitrogen (N) from nitrate (NO3−), which was the case for the Urea and DCD treatments, to ammonium (NH4+). The variations in soil temperature, moisture and NO3− content regulated the seasonal fluctuations of N2O emissions. Moreover, the DCD treatment did not significantly affect N2O or agronomic NUE relative to the Urea treatment, while CP and BNI significantly decreased annual N2O emissions by 16.5% and 18.1% and improved NUE by 12.6% and 6.7%, respectively. Thus, a markedly lower global warming potential (GWP) and greenhouse gas intensity (GHGI) was observed in the CP and BNI treatments relative to the Urea and DCD treatments. The results demonstrated that the NIs played important roles in enhancing yields and reducing N2O emissions from the vegetable ecosystem and that the CP and BNI treatments are suitable for marketing in China.