Impacts of salinity on the stability of soil organic carbon in the croplands of the Yellow River Delta

Abstract This study aims to improve our understanding of the mechanisms regulating the stability of soil organic carbon (SOC) in saline–alkaline soils. We hypothesized that desorption of SOC is greater in higher salinity/higher pH soils, and the higher level of soil inorganic carbon (SIC) leads to enhanced SOC stability (or weaker SOC desorption) in saline–alkaline soils like those of the Yellow River Delta (YRD). We collected soils from 23 cropland sites (from 0–100 cm) along three lines (upper, middle, and lower lines, with different salinity) across the Yellow River, which have high pH (7.97–9.02). We analyzed SOC, SIC, and water‐extractable organic carbon (WEOC) and salts. Our data showed a large range in SOC (2.3–11.7 kg C m −2 ) and SIC stocks (13.3–24.7 kg C m −2 ) over 0–100 cm. The lowest SOC and SIC stocks were found in the lower YRD where soil pH was highest (8.6–9.0). WEOC:SOC ratio (an indicator for SOC desorption) was greater in soils with higher pH, lower SIC, and/or water‐extractable Ca 2+ plus Mg 2+ , indicating that SOC stability is weak in high salinity/high pH soils, but high levels of SIC or Ca 2+ /Mg 2+ can increase SOC stability. Our study suggests that amelioration practice may lead to an increase in both SOC and SIC stocks in saline–alkaline soils.