Abstract: To examine the impacts of grass-planting on soil bacterial diversity in apple orchard, high-throughput sequencing technology was used to analyze bacterial community and composition of specific bacteria genera in top soil (0-10 cm) in a 13-year-old Qinguan apple orchard under planting different grass species including orchard grass (Dactylis glomerata), white clover (Trifolium repens) and alfalfa (Medicago sativa) in Longdong arid region, Gansu. The results showed that the top three phyla with highest relative abundance were Proteobacteria (48%-52%), Bacteroidetes (14%-19%) and Acidobacteria (10%-17%) under the three grassplanting models. Compared to the control, the relative abundance of Betaproteobacteria increased by 19%-38%,Flavobacteriia by 31%-65%, Lysobacter by 37%-93% and Phenylobacterium by 45%-52% respectively under different grass-planting patterns. Clostridium, which promotes soil nitrogen accumulation, was observed only in the orchard grass treatment. Nannocystis, favoring organically rich environments, existed only in the white clover treatment. Bacillus, which has a strong association with plant nitrogen fixation, mainly occurred in the soil where white clover and alfalfa were cultivated. Our results suggested that soil bacteria diversity increased under grass-planting in the apple orchard. Grass-planting can promote the occurrence of specific beneficial bacteria in the soil and thus play a role in regulating soil microenvironment.

Key words: re-watering, compensation effect, drought stress, source-sink