Systematic relationship between soil properties and organic carbon mineralization based on structural equation modeling analysis

Previous studies have focused mostly on the effects of the single application of biochar on soil organic carbon mineralization. However, these studies were not able to infer the effect of extended biochar supplementation at distinct concentrations on the systematic relationship between soil properties and organic carbon mineralization. Thus, we investigated the soil characteristics, such as organic carbon mineralization, hydraulics, aggregation, and microbiota under the biochar supplementation for an experimental period of six years in a rapeseed-sweet potato rotation field experiment in upland red soil in southeast China. The structural equation modeling (SEM) was constructed to reflect the systematic relationship between soil properties and organic carbon mineralization. The results of our study revealed that the biochar significantly reduces the soil bulk density and enhances the soil water holding capacity, but these effects diminished with the time. We also found that low-medium biochar application rates (0.5% and 1%) considerably increased the soil microbiota, aggregation, and potentially mineralizable carbon (C0). Moreover, high application rates (2%) of biochar inhibited the carbon mineralization and increased the soil organic carbon fixation. Besides, the outcome of SEM demonstrated that the hydraulics, aggregation, and microbiome of soil impacted the C0. The effects of soil aggregation and microbiota on C0 were higher during 2014–2016 than they were in 2011–2013, and the negative impact of soil hydraulics on C0 diminished with time. In conclusion, the effects of biochar on physicochemical characteristics and organic carbon mineralization of soil differ with the dosage and duration of biochar supplementation. Also, a high dose of biochar addition can substantially reduce CO2 emission from soil to the atmosphere. [Display omitted] •Biochar significantly enhance hydraulics properties, while the effects weakened over time.•Low-medium dose of biochar can improve the soil aggregates stability and soil microorganisms.•High dose biochar can inhibit the carbon mineralization and increase the fixation of soil organic carbon.•SEM can well reflect the systematic relationship between soil organic carbon mineralization and soil properties.