Effects of biochar and manure amendments on soil microbial communities and crop yield in yellow cinnamon soil

Long-term chemical fertilization degrades soil properties and reduces microbial diversity, posing a significant threat to sustainable crop production. Yellow cinnamon soil is widespread across China, yet its weak structure and lower fertility substantially constrain crop productivity.

To address this challenge, we conducted a long-term experiment on yellow cinnamon soil to evaluate the individual and synergistic effects of biochar and manure amendments on soil fertility, microbial communities and wheat yield. Six treatments were established, namely unfertilized control (CK), biochar alone (B), mineral fertilizer (NPK), biochar plus mineral fertilizer (NPKB), partial manure substitution for mineral N (NPKM), and combined biochar with partial manure substitution (NPKMB).

Our results showed that organic amendments markedly improved soil fertility, crop productivity, and microbial community structure. NPKM significantly elevated nutrient contents, alleviated acidification induced by mineral fertilizers, and reduced soil bulk density, and ultimately raised wheat and maize yield by 6.68% and 9.12%, respectively. NPKMB amplified these benefits and raised wheat and maize yield by 85.56% and 67.64% over the CK treatment. With respect to microbial responses, exclusively mineral fertilization lowered microbial diversity and altered community composition, whereas adding biochar and manure restored microbial richness and diversity to levels comparable to those in unfertilized soil. Notably, the NPKMB treatment enriched potentially beneficial biomarkers, including Devosia, Porphyrobacter, Reyranella, Trechispora, and Pyrenochaetopsis.

These taxa correlated positively with AK, AP, NH₄⁺-N, SOC, underscoring their potential roles in nutrient mobilization and plant growth promotion. Overall, NPKMB offers an effective sustainable strategy for managing yellow cinnamon soil. It improves soil physical and chemical quality, stimulates microbial activity, enriches beneficial taxa, and ultimately enhances wheat yield. These findings support optimized fertilization practices that enhance soil health and ecosystem function in yellow cinnamon soil regions.