Effects of cropping patterns and nitrogen application rates on soil microbial community characteristics in goji berry root zones

Abstract Goji berry planting in arid saline-alkali areas faces the challenges of soil micro-ecological imbalance and excessive application of nitrogen fertilizer. Objectives To clarify the interactive effects of different planting patterns and nitrogen application levels on the structure, diversity and function of soil microbial communities in the root zone of goji berry in arid saline-alkali areas, which is of great significance for optimizing the planting system of goji berry in this area and reducing nitrogen application rates and improving nitrogen use efficiency. Methods Based on field experiments, this study set up two planting patterns: goji berry monoculture and goji–alfalfa intercropping, four nitrogen application gradients: 0 kg·hm - ² (N0), 150 kg·hm - ² (N1), 300 kg·hm - ² (N2), and 450 kg·hm - ² (N3). The culturable microbial counts, community structure, diversity and functional genes of bacteria and fungi were analyzed by dilution coating plate method, high-throughput sequencing and functional prediction. Results: Compared with monoculture, the abundances of culturable soil bacteria and actinomycetes were significantly increased under the goji–alfalfa intercropping pattern, while the abundance of culturable fungi and the relative abundance of potential pathogens were inhibited, and the bacterial community structure was optimized. For example, the relative abundance of Proteobacteria decreased, and the proportion of Gemmatimonadota , Actinomycetota and Thermomicrobiota , increased. Diversity analysis showed that N1 treatment was beneficial to maintain the diversity and stability of bacterial and fungal communities in the goji-alfalfa pattern, while N3 treatment significantly inhibited microbial diversity in the goji berry monoculture pattern. The functional prediction showed that the function of bacteria was mainly amino acid metabolism and carbohydrate metabolism. The ILN1 treatment appeared to facilitate the transformation of fungi to mixed trophic strategies such as endophyte-plant pathogens , while the goji berry monoculture pattern tended to rely more heavily on saprophytic nutrition. Conclusions In the arid saline-alkali area, the nitrogen reduction management mode of goji-alfalfa intercropping with 150 kg·hm - ² could effectively reconstruct the microbial community in the root zone of goji berry. It is a suitable cultivation and nitrogen application management mode for the green and sustainable development of goji berry industry in this area.