Microbial community responses to feedstock type and modifications determine soil organic carbon sequestration and crop yield in biochar-amended arid soils

Abstract

Biochar amendment improves soil health and mitigates the impacts of climate change on agriculture by promoting sustained crop production. Biochar is modified to further optimize its agronomic and environmental benefits; however, the magnitude and mechanism of microbial community, soil organic carbon (SOC), and crop yield responses remain unclear. This study evaluated the impact of different feedstock-derived pristine biochars and their modifications on soil health, short-term SOC dynamics, and the relationship between these changes and crop productivity. Pine-derived pristine or unmodified biochar (BC), carbon dioxide-modified biochar (C-BC), sulfur-modified biochar (S-BC), and poultry litter biochar (P-BC) were applied to the soil (1% w/w), and sorghum (Sorghum bicolor) was cultivated for three months in greenhouse conditions. Pine biochar nearly doubled short-term SOC storage, with BC, C-BC, and S-BC accumulating 97%, 105%, and 96% more SOC than the unamended soil, respectively, alongside increased particulate organic carbon (POC). Notably, BC increased soil fungal abundance by 16% compared to unamended soil. S-BC simultaneously enhanced short-term SOC accumulation and crop yields, with more significant positive effects on soil fungi, K, and S than C-BC, resulting in 9% and 13% greater grain yields than C-BC and unamended soil, respectively. In contrast, P-BC increased soil nutrient availability and grain yield but reduced microbial abundance (e.g., soil fungi) and SOC accumulation in the short term, with these effects likely depending on application rate, experimental duration, and soil type. Modified pine biochar, specifically S-modified biochar, can enhance short-term SOC accumulation and improve productivity in low-fertility arid soils by boosting microbial activity and improving nutrient cycling. While SOC storage was positively correlated with biochar C, C/N ratio, surface area, and pore volume, as well as with soil POC and microbial biomass C, the yield response was more closely related to biochar nutrient content and soil pH regulation.