Objectives We investigated the effects of strip fertilization distances to Korla fragrant pear tree trunks on soil nutrient spatial distribution and bacterial community structures, providing a theoretical basis for scientific water and fertilizer management in dense planted pear orchards.

Methods A field esperiment was conducted in a 11-year old Korla fragrant pear orchards under dense plantation in southern Xinjiang. Three distance treatments to pear tree trunks were setup for the strip fertilization ditches, including 60 cm, 90 cm, and 120 cm, denoted as F60, F90, and F120, respectively. Soil profiles were excavated at a horizontal distance of 45−135 cm away from the main trunk and a depth of 30−70 cm, the root morphology indicators were investigated using the WinRHIZO root analysis system, And soil organic matter, available nutrients, and the bacterial community composition were analyzed.

Results F60 treatment significantly promoted root growth, with fine root lengths 1.96 times and 1.95 times longer than F90 and F120, respectively, and conducting root lengths 2.13 times and 2.18 times longer than F90 and F120, respectively. In the soil profile, the total root length and total root surface area density of F60 treatment were significantly higher than those of F90 and F120 treatments, and the fine root length density and root surface area density were significantly higher than those of F90 treatment; Soil available N P, and K of each treatment were enriched in the fertilization ditch and decreased laterally, available P showed the highest spatial heterogeneity, the difference between the fertilization area and the adjacent area was significant. In the vertical direction, the distribution of organic matter and available nutrients in different treatments all showed high in top and low in bottom. The dominant bacterial communities in the rhizosphere soil of pear trees were in order of Proteobacteria (41.2%), Actinobacteria (15.7%), Firmicutes (10.0%), Bacteroidetes (8.3%), and Chloroflexi (6.8%), accounting for 82.0% of the total microbial community. The fertilization distance affected the structure of soil bacterial communities, all the treatments increased the relative abundance of Proteobacteria and Bacteroidetes within fertilized area than nearby area, F60 significantly treatment increased the relative abundance of Proteobacteria and Firmicutes, while decreasing the relative abundance of Actinobacteria. Fine root and transport root length density positively correlated (P<0.05) with available N, available K, and Firmicutes, with correlation coefficients ranging from 0.49−0.63, and negatively correlated (P<0.01) with Actinobacteria, with correlation coefficients of −0.77 and −0.83, respectively. Root system density, soil nutrients, and bacterial community composition were closely related to soil depth (P<0.05), not significantly correlated with horizontal distance.

Conclusions Fertilization distance significantly influences the spatial distribution of root systems and nutrients in pear orchards, as well as the structure of regional microbial communities. Striped fertilization at 60 cm from the main trunk markedly promotes the growth of fine roots and conductive roots in the 30–50 cm deep soil layer, elevates the content of available nutrients in the soil at a horizontal distance of 45–75 cm from the main trunk, and enhances nutrient absorption and utilization by the root system. Although fertilization distance does not alter soil microbial diversity, strip application at 60 cm from the pear tree significantly increases the relative abundance of Proteobacteria and Firmicutes in the dominant soil bacterial groups compared to application at greater distances, while reducing the relative abundance of Actinobacteria. Therefore, the impact of fertilization distance on microbial diversity requires long-term monitoring.