Unveiling the double-edged sword effect of saline water irrigation through meta-analysis: Reduced soil organic carbon storage versus mitigated CO2 and N2O emissions

Saline water irrigation serves as a critical strategy for sustainable agriculture amid freshwater scarcity. While its growing application, the effects of saline water irrigation on soil organic carbon (SOC) storage and CO 2 and N 2 O emissions remain inconsistent and poorly quantified. This study aims to address this knowledge gap through a meta-analysis of 50 studies encompassing 374 field observations, with the specific objective of evaluating the impacts of saline water irrigation on SOC content, as well as on emissions of CO 2 and N 2 O, considering factors such as climate, soil properties, crop types and agronomic practices. Results showed that relative to freshwater irrigation, saline water irrigation reduced SOC content by 10.2 % and CO 2 and N 2 O emissions by 19.1 % and 13.8 %. Saline water with electrical conductivity greater than 8 dS·m −1 intensified this effect, reducing CO 2 and N 2 O emissions by 32.3 % and 31.4 %. This finding suggests that saline water irrigation markedly reduce CO 2 and N 2 O emissions in arid or semi-arid regions. Saline water irrigation in soils with bulk density below 1.35 g·cm −3 and total nitrogen content above 1 g·kg −1 promoted the reduction of CO 2 and N 2 O emissions and delayed SOC losses. Cash crops outperformed grain crops in SOC retention and CO 2 and N 2 O emissions reduction under saline water irrigation. Additionally, furrow irrigation and a nitrogen application rate below 150 kg·ha −1 demonstrated superior potential CO 2 and N 2 O emissions mitigation. Future agronomic management should be optimized based on regional climate and soil characteristics to promote SOC sequestration and climate-smart agriculture. This current research demonstrated that saline water irrigation is a viable strategy for regions with limited freshwater availability, providing a practical approach to both transforming agricultural systems and reducing emissions of CO 2 and N 2 O. • Saline water irrigation decreases SOC content while mitigates CO 2 and N 2 O emissions. • Cash crops under saline water irrigation have better carbon sequestration and emission reduction. • Irrigation water EC as the key determinant that dominates SOC content, CO 2 and N 2 O emissions. • Crop types and agronomic practices strongly affect CO 2 and N 2 O emissions dynamics.