Evaluation of the feasibility of fertilizer deep-placement for N2O mitigation and soil fertility improvement in rice paddies of Chungnam provinces

Nitrogen (N) losses occur primarily through N fertilization to the agricultural soil surface, while their efficiencies varied from various N fertilization strategies, including types, amounts, and fertilization methods.This field-based study aimed to evaluate the individual or combined effects of fertilizer deep-placement (FDP), which input N fertilizers to a soil depth of 20 -30 cm, technique with 20% reduced N fertilization on N 2 O emissions and soil chemical properties in irrigated paddy soils.For assessing their N 2 O reduction efficiency, treatment groups were divided as follows: conventional N fertilization (control), FDP, and FDP application with 20% reduced N fertilization (FDP rf ).Soil total nitrogen and NH 4 + concentrations were increased by the FDP application, while the decrease in soil NO 3 -content was revealed.Additionally, the individual FDP amendment led significantly to decrease the soil organic matter content, resulting from the lowest value at 17.6 g kg -1 .However, the co-application of FDP technique and 20% reduced N narrowed not only decreasing FDP-induced variations but also enhancing the availability of soil phosphorus and calcium compared to the conventional fertilization method.The highest daily N 2 O emission was observed in the control treatment (87.2 g ha -1 day -1 ), while FDP and FDP rf treatments reduced this to 64.7 g ha -1 day -1 and 51.3 g ha -1 day -1 , respectively.In addition, cumulative N 2 O emission was reduced by 27% with the FDP application, while statistically significant differences were not observed between FDP and FDP rf treatments.These findings suggest that the FDP technique effectively mitigates the N 2 O emissions by N stabilizing (in the form of NH 4 + ) and maintaining favorable soil environments.However, for developing FDP-based sustainable and climateresilient agricultural approaches, the findings of our study suggest the FDP application with additional organic matter supply.