Specific protistan consumers and parasites are responsive to inorganic fertilization in rhizosphere and bulk soils

Purpose Protists play important roles in soils by regulating organic matter decomposition, catalysing biogeochemical nutrient cycling processes and maintaining soil fertility and plant productivity, but they remain poorly characterized in the plant-soil system under long-term intensive agricultural management. Methods We investigated the impacts of multiple inorganic fertilization regimes on the diversity, composition and potential functions of protists and their interactions with bacteria and fungi in the rhizosphere and bulk soils of sorghum plants in a long-term field experiment. Results Protists were dominated by the supergroups Rhizaria, Stramenopiles, Alveolata, Amoebozoa and Archaeplastida in both rhizosphere and bulk soils. The diversity of protists was significantly lower in rhizosphere than bulk soils, and the community compositions of total protists were remarkably different in the two compartments. Inorganic fertilization had no significant impacts on the total protistan diversity or compositions but significantly changed the relative abundances of specific taxa of consumers and parasites. Protists were significantly correlated with bacteria and fungi as revealed by the co-occurrence network analysis, indicating their intensive trophic interactions with bacteria and fungi in soil food webs. Soil properties and the community compositions of bacteria and fungi were important factors shaping the variation in the protistan communities, as revealed by variation partitioning modelling analysis. Conclusion Altogether, we provide new information for the impacts of fertilization on the protist communities in rhizosphere and bulk soils and identified specific functional groups of protists that are most responsive to long-term agricultural management.

Automated summary

This study investigated the impacts of inorganic fertilization regimes on protist communities in rhizosphere and bulk soils of sorghum plants. Results showed that protists were dominated by specific supergroups in both compartments, with significantly lower diversity in rhizosphere soils. Inorganic fertilization did not significantly impact protistan diversity or composition, but did change the relative abundances of specific taxa. Co-occurrence network analysis revealed intensive trophic interactions between protists, bacteria, and fungi in soil food webs. Soil properties and the community compositions of bacteria and fungi were important factors shaping protistan communities.