Soil type and wetting intensity control the enhancement extent of N2O efflux in soil with drought and rewetting cycles

Climate change alters the intensity and frequency of drought and rewetting (D/W) events; however, the influence patterns of D/W on soil N₂O efflux in the water-limited area were not fully understood. Therefore, the impacts of D/W cycles varying in different extent of rewetting and frequency to N₂O efflux in two kinds of soil on the Loess Plateau were investigated. The incubation conditions consisted of 1) D/W treatments with four 7-day cycles from 10% water holding capacity (WHC) to 60%WHC or 90%WHC, 2) constant moisture of 60%WHC and 90%WHC. The pulse of N₂O efflux rate under 10−60%WHC treatment was higher than that under 10−90%WHC treatment in calcic cambisols, while opposite trend was observed in earth-cumuli-orthic anthrosols. Meanwhile, the pulse of N₂O efflux rate decreased as cycle number increased for different wetting intensities and soil types. The direct N₂O efflux under 10−60%WHC and 10−90%WHC treatments were 5.49 and 1.89 μg N₂O–N g⁻¹ soil in calcic cambisols, with those being 1.92 and 10.85 μg N₂O–N g⁻¹ soil in earth-cumuli-orthic anthrosols, respectively. The N loss in earth-cumuli-orthic anthrosols was approximately 5.74 times greater than that in calcic cambisols under 10−90%WHC treatment, whereas the N loss under 10−60%WHC treatment was about 2.86 times greater in calcic cambisols than that in earth-cumuli-orthic anthrosols. This study suggested that extreme rainfall events can enhance the N₂O efflux and N loss in agricultural soils on the Loess Plateau in terms of soil type and wetting intensity, which should not be ignored in the N fertilizer management.