Microbial metabolism strengths carbon sequestration and crop yield in upland red soil after long-term ex situ incorporation of straw

Incorporating rice straw into upland has been adopted as a strategy to increase crop productivity and decrease poisoning to rice from reducing substances accumulation as well as mitigate methane emission from paddy fields in South China. However, the mechanism underlying long-term ex situ incorporation of rice straw in upland on soil organic carbon (SOC) and crop yields through microbial metabolism remains unclear.

Hence, a field experiment was established to investigate the response mechanism of SOC and crop yields underlying microbe-mediated carbon dynamics with nutrient stoichiometry by ex situ incorporation of rice straw in upland.

The results showed that the treatment of cropping with chemical fertilizers plus rice straw (SCF) had the highest SOC accumulation rate (0.14 ± 0.03 g C kg⁻¹ yr⁻¹) during the 22-year experimental period. The mean yields of rapeseed and sweet potato were increased by 5.0% and 4.7% in the SCF treatment, correspondingly, compared with the treatment of cropping with chemical fertilizers (CF). Additionally, based on ecoenzymatic stoichiometry, soil microorganisms were found to be co-limited by carbon and phosphorus, which was aggravated by the decrease of soil available nutrients. The SCF treatment exhibited a higher soil microbiomass, resulting in an increased secretion of ecoenzymatic activities to mediate stoichiometric imbalance and mitigate nutrient competition between plant and microbial nutrient limitations. The findings revealed a significant association between stoichiometric imbalance and both SOC and crop yields, respectively.

Therefore, our study indicated that long-term ex situ incorporation of rice straw in upland could be adopted as an effective agricultural management strategy to improve SOC and crop yields.