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

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  • 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 CO2 and N2O 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 CO2 and N2O, 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 CO2 and N2O emissions by 19.1 % and 13.8 %. Saline water with electrical conductivity greater than 8 dS center dot m- 1 intensified this effect, reducing CO2 and N2O emissions by 32.3 % and 31.4 %. This finding suggests that saline water irrigation markedly reduce CO2 and N2O emissions in arid or semi-arid regions. Saline water irrigation in soils with bulk density below 1.35 g center dot cm-3 and total nitrogen content above 1 g center dot kg- 1 promoted the reduction of CO2 and N2O emissions and delayed SOC losses. Cash crops outperformed grain crops in SOC retention and CO2 and N2O emissions reduction under saline water irrigation. Additionally, furrow irrigation and a nitrogen application rate below 150 kg center dot ha- 1 demonstrated superior potential CO2 and N2O 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 CO2 and N2O.