Different effects of NaCl and Na2SO4 on soil net nitrogen mineralization in coastal wetlands

NaCl and Na2SO4 are the foremost salt compositions in coastal wetlands, while their effects on soil net nitrogen mineralization still remain unclear. Aimed at investigating the two salt compositions on soil net nitrogen mineralization, a 30-day laboratory incubation experiment was respectively conducted by adding 5% NaCl and Na2SO4 to incubated coastal wetland soils under aerobic conditions. Our results showed that Na2SO4 addition increased the rates of mineralization (R-min) by an average of 33.03% and nitrification (R-nit) by 23.84% during the incubation (p < 0.05). In contrast, NaCl addition significantly reduced R-min by 71% and R-nit by 44% at day 7 (p < 0.05). The activities of fluorescein diacetate, arylamidase and urease in Na2SO4 addition treatments were higher than those in NaCl addition treatment. These results demonstrated the ion-specific effects of salt type on nitrogen mineralization rates and enzyme activities.