Effect of Reduced Chemical Fertilizers with Biochar Application on Microbial Community in Rhizosphere Soil of Amorphophallus konjac

In agricultural applications, biochar showed potentials to improve soil properties. At present, effects of chemical fertilizer reduction with biochar application on the microbial community in the rhizosphere soil need to be further investigated. In this study, konjac (Amorphophallus konjac K. Koch) was taken as the research subject, and analyzing the microbial α-diversity, amplicon sequence variants (ASVs) community composition in rhizosphere were analyzed using high-throughput sequencing technology, and tuber yield was calculated. Four treatments of chemical fertilizer with biochar application were set, T1: common fertilizer 20 g/plant, T2: common fertilizer 10 g/plant, T3: controlled-release fertilizers 10 g/plant, T4: controlled-release fertilizers 10 g/plant with biochar 100 g/plant. The results found that, the Chao1 index, number of unique ASVs, and total ASV of rhizosphere soil bacteria in T2 increased by 14.45, 13.39, and 14.36% respectively, compared to T1; while that of fungal abundance decreased by 17.82, 48.28, and 18.42%. Similarly, compared to T3, the Chao1 index, number of unique ASVs, and total ASV in bacterial of rhizosphere soil in T4 increased by 9.36, 19.88, and 9.81%, respectively, while that of fungal abundance decreased by 9.16, 20.18, and 9.62%. The yield of konjac showed no significant difference between T1 and T2 treatments. However, T4 treatment had a significantly higher yield than T3 treatment (P = 0.076), and T4 treatment was significantly higher than T1 treatment (P < 0.05). The results indicated that chemical fertilizer reduction with biochar application can improve bacterial abundance and unique and total ASVs in the rhizosphere soil of konjac, while reducing fungal abundance and unique and total ASVs. This can effectively promote the transformation of the rhizosphere soil towards a high-fertilizer “bacterial type”, leading to an increase in the yield of konjac.