ABSTRACT Although straw is widely used to ameliorate saline soils, the impact of salinity on straw conversion into soil organic carbon (SOC) fractions remains unclear. Our aim was to explore how soil salinity affected straw conversion into SOC. A 180‐day soil incubation with 13 C‐labeling maize straw was conducted to investigate straw conversion into free particulate organic carbon (fPOC), occluded particulate organic carbon (oPOC), and mineral‐associated organic carbon (MAOC) under different salinity levels. Four soil salinity levels were arranged: 3 (LS), 5 (MS), 10 (HS), and 15 g kg −1 (SS), and 5.0% of 13 C‐labeling straw was added to each treatment. Straw conversion into fPOC was significantly positively associated with salinity level, while straw‐derived oPOC and MAOC significantly decreased with increasing salinity ( p < 0.05). This clearly indicated that high salinity could favor fPOC accumulation, but lower the capability of soil carbon sequestration. Meanwhile, C/N ratio of SOC significantly decreased with salinity rising ( p < 0.05), reflecting that the composition of SOC pool was obviously affected by salinity. Furthermore, soil dehydrogenase, cellulase, and β ‐glucosidase activities decreased significantly with salinity rising ( p < 0.05), suggesting that salinity inhibited microbially derived SOC formation during straw decomposition. Overall, our findings first discover the specific influence of soil salinity on straw conversion into SOC, which can provide a more comprehensive understanding of the capability of soil carbon sequestration under different saline conditions.
Xie et al. (Thu,) studied this question.