Spatiotemporal Evolution of Soil Quality Under Long-Term Apple Cultivation in the Taihang Mountains, China

The present study aims to investigate the impact of long-term apple production and orchard management practices on soil quality in gneiss mountainous regions. The microbial community (as measured by phospholipid fatty acid analysis) and soil physicochemical properties (bulk density, organic matter, nitrogen, phosphorus, and potassium) were determined in soil samples collected from apple plantations of various ages (0-, 8-, 22-, 29-, and 36-year) in Gangdi Village, Xingtai, China. The soil samples were collected from depths of 0–20, 20–40, and 40–60 cm. The findings of the present study demonstrate that with increasing duration of apple cultivation, the soil bulk density and porosity decreased and increased, respectively. Initially, the content of soil nutrients such as organic matter, nitrogen, and phosphorus increased, eventually stabilizing, accompanied by a decline in pH. The soil microbial biomass significantly increased, accompanied by discernible alterations in the composition of the microbial community. Organic matter was found to be the primary factor influencing the structure and diversity of microbial communities. It is evident from forward analysis that the soil Gram-negative and actinomycete communities were predominantly influenced by soil pH, bulk density, and total phosphorus. In contrast, the Gram-positive and eukaryote communities were less affected by soil environmental factors. Notably, the soil bacterial community presented a greater degree of sensitivity to the duration of apple cultivation than did the fungal community. A marked vertical difference in the soil quality indicators was evident, with the increase in surface soil quality exceeding that of deeper soil depths.