LAUSR

Abstract The aim of this experiment was to explore the effects of Allium fistulosum-Brassica juncea-Triticum aestivum rotation on the soil microbial environment and the growth of young apple trees under field conditions. After rotation with A. fistulosum-B. juncea-T. aestivum a year, the β-diversity of soil fungi differed, and there were significant differences in fungal community structure. In addition, cultivable fungi decreased, the ratio of bacteria to fungi increased, and the maximum value was achieved after rotation with B. juncea. The percentage of Fusarium spp. decreased to 1.82%, 1.61%, and 3.32% in Dashaling, Feng Maozhai, and Wantou Village, respectively. The gene copy number of Fusarium oxysporum and Fusarium solani was reduced by 20–50%; the content of phenolic acids, which was mostly phloridzin, decreased significantly by 64.24%, 58.59%, and 71.67% in Dashaling, Feng Maozhai, and Wantou Village, respectively, and the rotation with A. fistulosum resulted in the greatest reduction. The root extracts of A. fistulosum, B. juncea, and T. aestivum inhibited the mycelial growth of four Fusarium species; the root extract of A. fistulosum showed the largest degree of inhibition, followed by B. juncea and T. aestivum. Compared with continuous cropping, the yield was significantly increased under crop rotation, and fruit quality was also enhanced. Thus, A. fistulosum-B. juncea-T. aestivum rotation within a year can promote the growth and yield of young apple trees, reduce the copy number of harmful Fusarium, and changed the structure of the soil microbial community.