Biological nitrification inhibitor for reducing N2O and NH3 emissions simultaneously under root zone fertilization in a Chinese rice field

Abstract

Rice fields significantly contribute to the global N2O and NH3 emissions. Nitrification inhibitors (NIs) show promise in decreasing N2O emission, but they can increase NH3 volatilization under traditional broadcasting. Root zone fertilization (RZF) can mitigate NH3 volatilization, but it may pose a high risk to N2O emission. Additionally, most chemical NIs have limited availability and potential for environmental contamination, in contrast, biological NIs, such as methyl 3-(4-hydroxyphenyl) propionate (MHPP), are easily available and eco-friendly. However, the effects of RZF combined with MHPP on N2O and NH3 emissions are unknown. Therefore, a field experiment was conducted in a Chinese rice field with five treatments at 210 kg urea-N ha−1 (BC: 3-split surface broadcasting; BC + MHPP: BC with MHPP; RZ, root zone fertilization; RZ + MHPP, RZF with MHPP; RZ + MHPP + NBPT, RZF with MHPP and NBPT). The results showed that although RZ eliminated NH3 volatilization, it significantly increased total N2O emission by 761% compared with BC due to the stimulation of nitrification by mid-season aeration (MSA) and the trigger of denitrification by a large amount of NO3−. Nearly 90% N2O was emitted at MSA stage for RZF treatments, and their N2O fluxes were exponentially related to the soil NO3−-N concentrations in the 7–20 cm deep soil layer. RZ + MHPP greatly reduced the peak values of N2O flux due to the suppression of nitrification by MHPP and then less production of NO3− for denitrification, its total N2O emission was 79% lower compared with that of RZ. However, RZ + MHPP + NBPT further increased the total N2O emission by 1044% compared with that of BC. Compared to BC, the RZF practice reduced total NH3 volatilization by 88–92% regardless use of NIs. RZF had no influence on CH4 emissions and enhanced the rice yields. In conclusion, RZF + MHPP is a promising strategy for simultaneously reducing N2O and NH3 emissions in rice fields.