Objective Effect of organic tea cultivation on the phoD bacteria, which relate to the regulation of phosphorus (P) cycling in soil through the secretion of alkaline phosphomonoesterases, was studied by comparing 3 different farming operation modes on the land.

Method The characteristics of the phoD-harboring bacteria communities in the topsoil (0-20 cm) of a virgin forestland (WD), a conventional tea plantation (CT), and an organically farmed plantation (OT) were compared using Illumina MiSeq sequencing technology. The bacterial diversity, community structure, and affecting factors were statistically analyzed by methods of Spearman correlation, distance-based redundancy (db-RDA), linear discriminant analysis effect size (LEfSe), and principal component (PCA).

Result Taking WD as the baseline for the comparison, long-term fertilization applied on the plantations acidified the soil causing pH to decrease by 0.46 to 0.61 units and a rapid rise on available P in the soil at CT to 484.3 mg·kg⁻¹. Meanwhile, the alpha diversity, except Simpson index, of the phoD-harboring bacteria community significantly declined as those of the CT and OT soils did not differ significantly (P>0.05). A total of 15 phyla, 27 classes, 50 orders, 67 families, 99 genera, and 195 species of phoD-harboring bacteria were detected in the topsoil samples collected from the 3 sites. In them, the dominant phyla included the unclassified, Proteobacteria, the unclassified_d_bacteria, and Actinobacteria, while the dominant genera, AD3, the unclassified, the unclassified_d_bacteria, and Bradyrhizobium. The LEfSe analysis showed 31 biomarkers to be sensitive to variations of soil due to different planting practices; PCA indicated distinctly varied community structures among the sites of different cultivation modes; and Spearman correlation and db-RDA identified total nitrogen, alkaline nitrogen, total potassium, and pH to be the main factors affecting the abundance and diversity of the phoD-harboring bacterial community in the soil.

Conclusion After a forestland being converted for tea cultivation, along with the alteration on the soil physicochemical properties the diversity, composition, and structure of the phoD-harboring bacterial community in the soil also underwent significant changes.