Optimizing biochar selection for soil amendment: Unraveling the feedstock-texture interplay for enhanced crop...

Biochar holds broad application prospects in soil amendment. However, its amendment efficacy highly depends on the precise compatibility between biochar feedstock and soil. To unravel this key interaction mechanism, this study systematically investigated the amendment effects of biochars derived from three feedstocks (corncob biochar (CB), watermelon peel biochar (WB), and sludge biochar (SLB)) on three soil textures: loam, clay, and sand. The characterization results showed that the three biochars exhibited significant differences in elemental composition, functional groups, and pore structure, indicating their distinct soil functions. Further pot experiments demonstrated that the amendment effects of biochar were highly specific to soil texture. Specifically, CB significantly increased the total organic carbon in loam by 54.32% and increased crop biomass by 62.50%. These changes are accompanied by optimization of the soil microbial community and an increase in the predicted relative abundance of functional genes phoD, rbcL, and gpx. WB improved the porosity of clay by 13.79% and enhanced available potassium (AK) by 11.28%. The predicted relative abundance of functional genes arcB, phoD, and gpx increased, ultimately resulting in a 95.01% increase in crop biomass. In sand, WB increased the cation exchange capacity and AK by 71.30% and 62.86%, respectively. Meanwhile, the increase in the predicted relative abundance of the functional gene rbcL indicated an enhancement in the photosynthetic carbon sequestration capacity of sand. The final crop biomass increased by 49.12%. This work is expected to provide theoretical basis and practical strategies for tailoring biochar feedstock selection to soil-specific characteristics.