Strong nutrient limitation of rhizosphere microorganisms lowers vegetable yield sensitivity to fertilization regimes

Rhizospheres recruit microorganisms to mediate nutrient transformation and enhance plant productivity. However, understanding is insufficient regarding the linkage between rhizosphere microbial nutrient limitation and crop yield sensitivity to fertilization regimes. Three kinds of Brassica vegetables (i.e., B. pekinensis L., B. campestris L., and B. chinensis L.) were cultivated to estimate sensitivity of vegetable yield to fertilization regimes, and molecular and statistical tools were adopted to disentangle landscape patterns of vegetable rhizosphere microorganisms. We found yields of Brassica vegetables responded largely differently to organic and inorganic fertilization treatments, and yield sensitivity to fertilization regimes was B. pekinensis L. > B. campestris L. > B. chinensis L. There were heterogeneous rhizosphere microenvironments between Brassica vegetables, showing significant differences in soil physicochemical properties, enzymatic activity, abundances of phosphorus-cycling genes, and community composition of rhizosphere bacteria and fungi. Rhizosphere microorganisms of Brassica vegetables displayed phosphorus limitation, and stronger microbial carbon and phosphorus limitations were found for rhizosphere of B. chinensis L. than rhizospheres of B. campestris L. and B. pekinensis L. Different vegetable rhizospheres displayed heterogenous landscape patterns of bacteria and fungi, showing notable differences in diversity and community structure as well as large divergence in coexistence patterns within bacteria and within fungi. Stochastic processes dominated community assemblages of rhizosphere bacteria and fungi, and rhizosphere bacteria and fungi showed opposite environmental constraint responding to vegetable yield sensitivity. Our results emphasized that a stronger nutrient limitation of rhizosphere microorganisms resulted in a more sensitive vegetable yield to fertilization regimes. Our findings enrich knowledge on nutrient limitation and diversity maintenance of microorganisms in vegetable rhizospheres, and these findings might guide precise fertilization to adjust rhizosphere microbial nutrient limitation to promote vegetable yield.