Saline water irrigation stimulate N2O emission from a drip-irrigated cotton field

Abstract

Farmers in arid regions often use saline irrigation water because fresh water supplies are limited. A field study was conducted to evaluate the effects of irrigation water salinity and N application rate on soil properties and N2O emission in a drip-irrigated cotton field. The experiment included three levels of irrigation water salinity (0.35, 4.61, or 8.04 dS m−1) and two N application rates (0 or 360 kg N ha−1). The results showed that soil moisture, salinity, and (Formula presented.) concentrations increased significantly as water salinity increased, whereas soil pH and (Formula presented.) concentrations decreased. N2O emissions on the first day, the first two days, and the first three days in the fertilized plots accounted for 19.5–26.3%, 68.1–70.5%, and 80.6–89.7% of total N2O emissions over the six days, respectively, while the corresponding proportions in the unfertilized plots were 13.5–23.2%, 40.5–51.7%, and 59.5–70.7%, respectively. In the unfertilized plots, N2O emission flux and cumulative N2O emission both increased as water salinity increased. In the fertilized plots, N2O emission rate and cumulative N2O emission were both highest in the 4.61 dS m−1 treatment and lowest in the 0.35 dS m−1 treatment. Correlation analysis showed that soil moisture, (Formula presented.) , and (Formula presented.) were positively correlated with N2O emission rate. In contrast, soil salinity and pH had no significant correlation with N2O emission rate. Our study demonstrates that irrigation with brackish or saline water (SW) significantly increased N2O emission. To reduce the adverse effects of brackish or SW irrigation on soil N2O emission, farmers should evaluate management practices such as additional irrigation before cultivation in spring, or the alternate use of fresh and SW during irrigation.