Ammonia fumigation combined with nitrogen inhibitor reduces root-knot nematode populations and N2O emission but not bacterial alpha diversity

Aqueous ammonia can release high nitrogen inorganic substances of ammonia and has been used as soil fumigant. However, the information about how fumigation with ammonia affects the soil microbial community is still limited. In this study, a laboratory microcosm experiment was conducted to evaluated the effectiveness of ammonia fumigation in controlling root-knot nematodes (RKNs), its influence on soil microbial diversity, and its impact on nitrous oxide (N2O) emissions. The results indicated that Ammonia treatment increased N2O emissions and decreased the RKNs population by 75.73%. Adding the inhibitors N-(N-butyl) thiophosphoric triamide (NBPT) and Dicyandiamide (DCD) to aqueous ammonia can mitigate N2O emissions. Compared with CK treatment, Soil enzyme activities, including those of urease, nitrate reductase, and nitrite reductase, were enhanced in each treatment. The fungal Sobs index was significantly higher in CK treatment than in the other treatments, whereas bacterial alpha diversity remained unaffected. This study also indicates that soil fumigation with aqueous ammonia has the potential to regulate fungal communities and important key reactions involved in nitrogen cycling.