Fertilization and rotation enhance tobacco yield by regulating soil physicochemical and microbial properties

Soil microbiome network structure is highly related to nutrient cycling and crop growth in agroecosystems. However, how agricultural practices influence soil microbial network structure and interact with co-varying soil properties, crop yield, and other microbial properties is still unclear. In the present study, soil physicochemical properties, microbial biomass and enzyme activity, and agronomic traits of tobacco were measured across seven fertilization treatments (Conventional Fertilization [CF], Incremental Fertilization [IF] 10 %, Reduced Fertilization [RF] 10 %, RF 20 %, CF combined with Rice Straw [CF + RS], RF 10 % combined with Green Manure [RF 10 % + GM], and No Fertilization [NF]) and two cropping treatments (continuous tobacco and corn-tobacco rotation). Microbial diversity and network structure were also characterized using Illumina MiSeq sequencing and network analysis. According to the results, cropping and fertilization treatments significantly affected twelve soil physicochemical properties and thirteen microbial properties. Among the microbial properties, the proportion of module hubs was most strongly correlated with tobacco yield (Pearson r = 0.613). Soil pH, cation exchange capacity (CEC), soil bacterial richness and module hubs constituted the best combination of variables that cumulatively explained 63.1 % of the variation in tobacco yield, among which module hubs individually explained 18.5 % of the variation in yield. Furthermore, the piecewise structural equation model showed that module hubs in microbial network were significantly affected by agricultural practices, and they indirectly drove tobacco yield by regulating soil properties. Overall, the results of the present study suggest that microbial properties (particularly network-associated keystone species) can mediate the effects of soil properties on crop yield, although the main influence or limiting factor for yield is still soil properties.