Abstract: The sustainable development of agriculture in arid and semiarid areas faces both drought stress and the negative impacts of continuous cropping. In the arid area of central Ningxia, artificial sand-covered soil provides favorable conditions for planting selenium-rich sand melon. However, long-term continuous cropping has led to the death of selfrooted seedlings in large areas, which can only be alleviated by grafting. There is a critical need for in depth understanding of the effects of different continuous cropping patterns on the structure of soil microbial community. In this study, the bacterial and fungal community structure of the artificial sandy layer and soil layer under different continuous cropping patterns were analyzed by Illumina MiSeqsequencing technology. The results showed that continuous cropping patterns and different soil layers significantly affected bacterial and fungal community structures. The genera with significant changes in the bacterial community of soil layers in the cropping mode S3 (self-rooted seedlings with continuous cropping for 11 years + sand replacement for 2 years + grafted seedlings with continuous cropping for 3 years) and S4 (selfrooted seedlings with continuous cropping for 12 years + grafted seedlings with continuous cropping for 4 years) included Streptomyces, Gaiella, Ensifer,Nordella, and Mesorhizobium; the genera with significant changes in fungal community structure mainly included Fusarium, Mortierella,Neocosmospora, Setophoma, Cladosporium, Chrysosporium,Periconia, Penicillium, and Sarocladium. Neocosmospora, Chrysosporium, and Lectera were enriched in the soil layer of S4 under continuous cropping, especiallyFusarium and Paracylindrocarpon. The relative abundance of Fusarium in S4 was significantly higher than that in S3. These results provide scientific data related to the imbalance in soil microbial community structure caused by different continuous cropping patterns.

Key words: arid area, sustainable agricultural development, continuous cropping obstacle, bacterial community structure, fungal community structure.