Asymmetries among soil fungicide residues, nitrous oxide emissions and microbiomes regulated by nitrification inhibitor at different moistures

Carbendazim is a widely used fungicide but causes widespread residues in soils and crops, and nitrous oxide (N2O) is one of the dominant greenhouse gases. The 3,4-dimethylpyrazole phosphate (DMPP), a nitrification inhibitor, might simultaneously affect fungicide dissipation and N2O emission. In this study, we applied the DMPP to agricultural soils contaminated with carbendazim under 60% and 90% soil water holding capacity (WHC) to quantify the carbendazim residues and N2O emission at various sampling times. The comprehensive linkages among N2O emission, microbial activities, community diversities, compositions and functional genes were quantified. Under 90% WHC, the DMPP applications significantly reduced carbendazim residues by 23.62% and 54.82% on days 10 and 20, respectively. The DMPP application also reduced soil N2O emission by 17.69% under 60% WHC and 98.68% under 90% WHC. The carbendazim residue was negatively related to soil NH4+-N, urease activity, and ratio of Bacteroidetes, Thaumarchaeota and Nitrospirae under 90% WHC, and the N2O emission rate was negatively related to NH4+-N content and relative abundance of Acidobacteria under the 60% WHC condition. In the whole (60% and 90% WHC together), the hao gene was negatively related to the carbendazim residue but positively related to the N2O emission rate. The asymmetric linkages among the carbendazim residue, N2O emission, microbial community and functional gene abundance were regulated by the DMPP application and soil moisture. The DMPP application had the promising potential to simultaneously reduce ecological risks of fungicide residues and N2O emissions via altering soil abiotic properties, microbial activity, and community and functional genes.

多菌灵(Carbendazim)是一种应用广泛的杀菌剂，但会在土壤与农作物中造成普遍残留；一氧化二氮(N₂O)则是主要温室气体之一。3,4-二甲基吡唑磷酸盐(DMPP)作为一种硝化抑制剂(nitrification inhibitor)，可同时影响杀菌剂的降解消散过程与N₂O排放。本研究将DMPP施加于受多菌灵污染的农田土壤，设置60%与90%土壤持水量(soil water holding capacity, WHC)两个水分梯度，于不同采样时间点定量测定多菌灵残留量与N₂O排放量，同时定量解析N₂O排放、微生物活性、群落多样性、群落组成与功能基因之间的综合关联。在90%WHC条件下，施加DMPP可使第10天和第20天的多菌灵残留量分别显著降低23.62%与54.82%；此外，DMPP施加还可使60%WHC条件下的土壤N₂O排放降低17.69%，90%WHC条件下降低98.68%。在90%WHC条件下，多菌灵残留量与土壤铵态氮(NH₄⁺-N)含量、脲酶活性(urease activity)以及拟杆菌门(Bacteroidetes)、奇古菌门(Thaumarchaeota)与硝化螺旋菌门(Nitrospirae)的丰度占比呈显著负相关；而在60%WHC条件下，N₂O排放速率则与土壤NH₄⁺-N含量及酸杆菌门(Acidobacteria)的相对丰度呈显著负相关。在整体分析（合并60%与90%WHC两组数据）中，hao基因(hao gene)与多菌灵残留量呈负相关，却与N₂O排放速率呈正相关。多菌灵残留量、N₂O排放、微生物群落及功能基因丰度之间的非对称关联，受DMPP施加与土壤水分状况共同调控。DMPP施加可通过改变土壤非生物特性、微生物活性、群落组成与功能基因，具备同时降低杀菌剂残留与N₂O排放生态风险的应用潜力。