Paper Details

Abstract

Brackish water irrigation is increasingly adopted in arid regions, yet its volume-dependent effects on soil carbon partitioning and ecosystem integrity remain unclear. In this study, we aimed to investigate the effects of brackish water irrigation (EC = 5.76 dS m⁻¹) on soil salinization and grassland productivity in a semi-arid saline-alkali ecosystem in Xinjiang, China. We determine an optimal irrigation volume, among 15 (C1), 30 (C2), and 45 (C3) L m⁻² year⁻¹, that balances biomass production against the risk of salt accumulation, thereby identifying a sustainable water management strategy for the region. The results showed that all irrigation treatments significantly increased total soil carbon compared to the rainfed control. However, organic and inorganic carbon pools exhibited sharply divergent responses to application rate. Moderate irrigation maximized soil organic carbon (SOC) accumulation in subsurface horizons (39–51% above control) and sustained a balanced SOC:SIC ratio (0.92). High-volume irrigation crossed a critical ecological threshold: species richness declined by 83%, aboveground biomass by 44%, and surface SOC decreased, while pedogenic carbonate accumulation drove the SOC:SIC ratio to 0.34 indicating strong inorganic carbon dominance. Furthermore, the irrigation volume governed soil inorganic carbon (SIC) dynamics, whereas vegetation cover controlled SOC patterns. The SOC:SIC ratio correlated positively with microbial biomass carbon (r = 0.78, p < 0.001) and negatively with bulk density (r=−0.65, p < 0.001), confirming that inorganic carbon dominance coincides with biological and structural degradation. These findings confirm that low-volume brackish water irrigation (≤30 L m⁻²) offers a viable strategy for rehabilitating degraded saline-alkali grasslands, whereas higher volumes risk promoting inorganic carbon accumulation at the expense of soil biological and structural integrity.

To Cite This Article