Mitigating soil nitrification and greenhouse gas emissions in non-paddy cropping systems by micro-molar hydrogen...

Non-paddy cropping systems play a significant role in food production. However, excessive nitrogen loss from non-paddy soils through nitrate leaching and ammonia volatilization poses a significant challenge to environmental sustainability. In this study, microcosm and field-scale experiments were conducted to explore the potential for using hydrogen peroxide (H₂O₂) to mitigate nitrogen loss and greenhouse gas emissions, aiming at filling gaps in knowledge regarding the underlying biochemical mechanisms. The results show that input of micromolar H₂O₂ from either artificial addition or natural rainwater into soils in the presence of magnetite (Fe₃O₄) could trigger Fenton-like reaction, which inhibited microbially mediated nitrification of soil-borne ammonium but did not affect the growth of the test crop plant (water spinach). In the absence of Fe₃O₄, input of rainwater-borne H₂O₂ into non-paddy soils caused reduction in the emissions of nitrous oxide (N₂O) and carbon dioxide (CO₂). There was a trend showing that the degree of reduction in N₂O and CO₂ fluxes increased with increasing concentration of rainwater-borne H₂O₂. It was likely that microbially mediated reduction of iron oxides took place during rainfall events, providing Fe(II) that is needed for reaction with rainwater-borne H₂O₂, triggering Fenton-like reaction to inhibit the soil microbes that mediate production of N₂O and CO₂ in the soils. The findings obtained from this study have implications for developing strategies to manage soil‑nitrogen to minimize its environmental impacts.