Burying straw interlayers decreases CO2 emissions in deep saline soil

Burying straw is an effective management to promote salt leaching and inhibit salt retention in the saline soils. However, the effects of buried straw interlayer on CO2 emission across soil depths remain unclear. Here, we investigated the variation in CO2 fluxes across soil depths (0–40 cm, 40–60 cm, 60–80 cm, 80–100 cm) under four straw interlayer levels (0, 6, 12, 18 Mg straw ha−1) based on a 7-year field experiment. We also quantified the priming effect on soil organic matter decomposition at deeper soils and its microbial driver. Soil CO2 concentration increased with soil depth and amount of straw, while soil CO2 fluxes decreased, especially at 40–60 cm and 60–80 cm. Higher levels of straw interlayer (12 and 18 Mg ha−1) reduced cumulative soil CO2 fluxes across 0–100 cm profile by 33.1 %–37.3 % compared to soil without straw interlayer. The effect size of straw interlayer on cumulative soil CO2 fluxes was more pronounced in deeper (40–60 cm) in relative to surface soil. The structural equation model suggested that soil volumetric water content positively correlated with the variation of soil CO2 fluxes at 0–40 cm. Conversely, a reduction in priming effect on soil organic matter decomposition under straw interlayer explained the inhibited effect of straw interlayer on cumulative soil CO2 fluxes at 40–60 cm compared to surface soil (0–40 cm). This study provides insight into the mechanisms of CO2 emission across the 0–100 cm soil profile in response to straw interlayer and demonstrated that higher amounts of straw interlayer had the potential to mitigate greenhouse gases emissions, making it a potential recommended agronomic practice for saline soils.