Fertilizers have a greater impact on the soil bacterial community than on the fungal community in a sandy farmland ecosystem, Inner Mongolia

Soil microorganisms play an important role in the energy flow and nutrient cycling between soil and plants, but the impact of fertilizers on soil bacterial and fungal communities in sandy agroecosystems remains uncertain. We hypothesized that fertilizers affect soil microbial communities through soil properties and plant leaf C:N:P stoichiometry. To test this hypothesis in a sandy farmland ecosystem on the Mongolian Plateau, soil microbial diversity and composition, soil properties and plant leaf C:N:P stoichiometry were examined following 4 years of one of six fertilizer treatments (no fertilizer; returning straw; chemical fertilizer; manure; half quantity of chemical fertilizer and manure; and half quantity of chemical fertilizer). The soil bacterial Shannon index was lowest with chemical fertilizer and half quantity of chemical fertilizer, while fungal Chao richness and phylogenetic diversity (PD) index were lowest with chemical fertilizer. However, chemical fertilizer combined with manure increased the soil bacterial Shannon and PD indices, while manure alone improved fungal Chao richness and the PD index. Fertilizers had a greater impact on the soil bacterial community than on the fungal community and the fungal community was more stable than the bacterial community. Based on redundancy analysis (RDA), total soil carbon, soil nitrogen, leaf carbon, leaf N:P, pH and 16S rRNA gene copy numbers affected the soil microbial community. Structural equation models (SEM) demonstrated that soil pH was a strong driving indicator of soil microbial community under fertilization in a sandy farmland ecosystem. Chemical fertilizer combined with manure out-performed other fertilizers in structuring soil bacterial communities, while chemical fertilizer alone was the worst in maintaining soil microbial communities. Results from this study provide a basis for fertilization management strategies in maintaining below-ground microbial diversity and in ensuring sustainable land development of sandy agroecosystems.