Long-term biochar-based fertilizer substitution promotes carbon, nitrogen, and phosphorus acquisition enzymes in dryland soils by affecting soil properties and regulating bacterial community

Biochar-based fertilizers have shown positive effects on soil function, an understanding of how long-term biochar-based fertilizers substitution affects soil properties, microbial communities, and enzyme activities in dryland is lacking. We investigated the impacts of seven years biochar-based fertilizer substitution on the soil properties, bacterial community, and carbon (C), nitrogen (N), and phosphorus (P) acquisition-related enzymes in a dryland cauliflower-maize rotation. Four fertilization strategies were set up: no fertilizer (CK), chemical fertilizer (CF), 30 % replacement of chemical N with biochar-based fertilizer (LBF), and 60 % replacement of chemical N with biochar-based fertilizer (HBF). Results elucidated that biochar-based fertilizer substitution treatments had higher soil organic C (SOC) and nutrients (N, P, and potassium (K)) than non-biochar-based fertilizer treatments. Biochar-based fertilizer substitution improved C-, N-, and P-acquiring enzyme activities and C:N enzyme ratio, but decreased C:P and N:P enzyme ratios. We further found that biochar-based fertilizer substitution altered the soil bacterial community diversity and composition. Soil properties and bacterial community explained most variations in C-, N-, and P-acquiring enzymes. Modeling analysis revealed that biocharbased fertilizer substitution had positive effects on soil properties and bacterial community, which further positively regulated soil C-, N-, and P-acquiring enzymes. Key factors driving enzyme variations included available P, SOC, available K, available N, total K, and total N, as well as soil bacterial community composition and diversity. In conclusion, biochar-based fertilizer substitution could enhance C-, N-, and P-acquiring enzyme activities by boosting soil nutrient levels and altering bacterial community in dryland fields.