Effects of Biochar-Based and Conventional Sheep Manure Organic Fertilizers on Soil Properties and Microbial Communities in a Moso Bamboo (Phyllostachys edulis) Forest in China

Fertilization is widely used in managed Moso bamboo (Phyllostachys edulis (Carrière) J.Houz.) forests in subtropical China, but its short-term effects on soil properties and microbiomes remain uncertain. In this study, we conducted a field experiment with four treatments: no fertilization (NF), compound fertilizer (CF), sheep manure organic fertilizer plus compound fertilizer (SOCF), and a biochar-based sheep manure organic fertilizer combined with compound fertilizer (BSOCF). Surface soils samples were collected approximately one year after the initial application, and soil properties were measured together with bacterial and fungal communities using high-throughput sequencing. Results showed that fertilization mainly affected soil chemical properties rather than overall microbial community structure. Compared with CF, BSOCF significantly increased soil pH (4.56 ± 0.10 vs. 4.30 ± 0.05) and resulted in the highest available phosphorus (AP, 6.38 ± 1.10 mg kg⁻¹) and available potassium (AK, 128.16 ± 17.56 mg kg⁻¹) contents. Microbial responses were comparatively limited. Bacterial richness remained stable, fungal alpha diversity showed only a weak increasing trend, and both beta diversity and phylum-level composition changed little among treatments. Variation in treatment-enriched taxa was associated mainly with soil pH and nutrient availability. Overall, the results indicate that biochar-based sheep manure organic fertilizer can improv soil fertility and partially alleviated soil acidity, while causing only limited short-term shifts in the overall microbial community structure. These findings suggest that BSOCF may be a suitable fertilization strategy for enhancing nutrient availability in Moso bamboo forests with relatively low short-term disturbance to soil microbial assemblages.