Differential N2O-Producing Activity of Soil Fungi Across Agricultural Systems: High in Vegetable Fields and Vineyards, Low in Paddies

The substrate-induced respiration-inhibition (SIRIN) method has been used to estimate fungi-derived N2O emissions, but its contribution to soil N2O emissions remains unclear. There is a need to quantify the fungal fraction of N2O production more precisely. Here, using isotopocule analysis, we assessed the relative contribution of fungi to soil N2O production potential under denitrifying conditions, where key limiting factors of denitrification (soil moisture, soil NO3−, and electron donor) were removed. The result showed that the ratio of fungi-derived N2O emissions (RF) was 0.83~4.28% in paddy soils, 13.80~23.21% in vineyard soils, and 15.34~65.94% in vegetable field soils, respectively. This indicated that the bacteria were the dominator of soil N2O production potential in most cases, but fungal pathways could be significant in vegetable field soils. The experiment with bactericide addition showed that inhibitors could affect non-target microorganisms in the SIRIN method. Our further analyses suggest that it is worth to explore the effect of soil organic carbon and microbial synergies on fungi-derived N2O emissions.