Faba bean in crop rotation shapes bacterial and fungal communities and nutrient contents under conventional tillage of triticale

Legumes in cropping sequence can strongly moderate soil biodiversity and its biochemical status, which could influence soil fertility and productivity. However, their impact on soil microbes and their relationships with soil chemical variables during the subsequent crop growth is not understood enough. In this study, we analyzed the changes in bacterial and fungal communities structure through 16S rRNA and ITS amplicon sequencing, respectively, across crop rotation with faba bean (faba bean-wheat-triticale, F) and without faba bean (wheat-wheat-triticale, W). Rhizosphere and bulk soil samples were taken during the triticale growth stages (stem elongation and maturity). Soil enzymatic activity and chemical properties were also determined. Study factors (crop rotation, soil compartment, growth stage) affected N, C, and P transformations, as indicated by the activity of soil enzymes, and F was more beneficial than W for protease, urease, and acid phosphomonoesterase activities, as opposed to cellulase activity. Changes in the chemical properties led to the shift in soil microbial communities with different bacterial and fungal communities' responses. F treatment enhanced the abundance of the bacterial genera representatives such as Streptomyces and Candidatus Udaeobacter while suppressing the abundance of Jatrophihabitans and Terrabacter. Crop rotation significantly influenced fungal genera and a greater abundance of Helgardia, Pseudogymnoascus, Monocillium, Fusarium, Chaetomium, and Vishniacozyma under F than W was noted and the adverse situation was noted for Peziza and Rhizopus. Rotation type significantly affected the alfa-diversity of the fungal, but not bacterial community. Beta-diversity analyses (nMDS, cluster) indicated that the main factor grouping samples were soil compartment and growth stage for the bacterial and fungal microbiome, respectively. The PERMANOVA results revealed significant effects of all factors on bacterial and fungal microbiomes. Different soil chemical variables governed bacterial and fungal communities. C_org, pH, P, Mg, and C_org, pH were the most important soil factors regulating bacterial and fungal community structure by crop rotation, respectively. Bacterial and fungal communities were more related to the content of N_tot in rotation with than without faba bean. The findings of this study contribute to a deeper insight into the relation between the faba bean in cropping sequence and soil microbiome, and modulation crucial soil conditions for the productivity of the successive crop.