Methane Uptake and Nitrous Oxide Emission in Saline Soil Showed High Sensitivity to Nitrogen Fertilization Addition

Abstract

Saline soils can significantly affect methane (CH4) and nitrous oxide (N2O) in atmospheric greenhouse gases (GHGs). However, the coupling effect of nitrogen fertilization addition and saline soils on CH4 uptake and N2O emissions has rarely been examined under various salinity conditions of soil. In this study, the effects of nitrogen fertilization addition on CH4 and N2O fluxes under different salinity conditions of soil in Hetao Irrigation District, Inner Mongolia, were investigated by on-site static chamber gas chromatography. A slightly saline soil (S1) (Electrical Conductivity: 0.74 dS m−1) and a strongly saline soil (S2) (EC: 2.60 dS m−1) were treated at three levels of nitrogen fertilization: a high fertilization rate of 350 kg N ha−1 (H), a low fertilization rate of 175 kg N ha−1 (L), and no fertilizer (control treatment, referred to as CK). Nitrogen application was the important factor affecting N2O emissions and CH4 uptake in saline soil. The CK, L, and H treatments exhibited a cumulative CH4 uptake of 156.8–171.9, 119.7–142.0, and 86.7–104.8 mg m−2 in S1, 139.3–176.0, 109.6–110.6, and 68.5–75.4 mg m−2 in S2, respectively. The cumulative N2O emissions under the L and H treatments in S2 were 44.1–44.7%, and 74.1–91.1% higher than those in S1. Nitrogen fertilizer application to saline soils reduced CH4 uptake and promoted N2O emission in the Hetao Plain, Inner Mongolia. Our results indicate that mitigating soil salinity and adopting appropriated fertilizer amounts may help to cope with global climate change.