Effects of Maize Potato Intercropping and Different Fertilization Methods on Rhizosphere Soil Microorganisms and Yield of Potato

A field experiment with three replicates was conducted to explore the effects of maize-potato intercropping and different nitrogen application strategies on rhizosphere soil microorganisms and potato yield. Microbial community analysis was based on relative abundance. Maize-potato intercropping improves land use efficiency, yet how differentiated nitrogen management regulates rhizosphere microecology and potato productivity in this system remains unclear. Clarifying nitrogen-mediated shifts in soil microbial communities under intercropping provides a theoretical basis for precise nutrient optimization. Five treatments were established: potato monoculture conventional fertilization (CK), intercropping intraspecific conventional nitrogen (T1), intercropping intraspecific reduced nitrogen (T2), intercropping interspecific conventional nitrogen (T3), intercropping interspecific reduced nitrogen (T4). We combined high-throughput sequencing, agronomic traits, and yield measurements to characterize rhizosphere microbial and crop responses. The findings revealed that, in terms of microbial community response, while treatment T3 significantly decreased bacterial community richness and diversity, Fungal communities were more sensitive to nitrogen reduction; Treatment T2 notably increased the relative abundance of the Proteobacteria phylum and Sphingomonas genus, maintaining high bacterial diversity. Fungal communities were more sensitive to nitrogen reduction; treatment T4 markedly lowered fungal richness, whereas treatment T1 promoted the proliferation of beneficial fungal groups, including those from the Mortierellomycota phylum. Regarding crop growth and yield formation, under treatment T3, the plant height of potatoes increased by 5.44% compared to CK, with both fresh and dry weights per tuber reaching their highest levels. Fresh tuber yield peaked in T3, showing a significant increase of 9.6% over CK, along with an elevation in the commercial tuber rate by 41.7%. Yield improvement was mainly attributed to larger tuber size rather than increased tuber number. The intercropping system compensated for a slight decrease in tuber number by optimizing individual tuber quality, which was associated with shifts in rhizosphere microbial community structure, achieving synergistic improvements in yield and quality. Under maize-potato intercropping, conventional interspecific fertilization (T3) can significantly enhance potato yield and commercial quality by regulating the rhizosphere microbial community structure, such as enriching functional bacteria like Parasegetibacter. Although nitrogen reduction treatments (T2, T4) maintained microbial diversity to some extent, they necessitate vigilance against potential pathogen proliferation risks. This research provides a theoretical basis for the microbially-driven mechanisms underlying reduced fertilizer input and increased efficiency in intercropping systems.