Although microbes influence plant growth, little is known about the impact of microbial diversity on plant fitness trade-offs, intraspecific-interactions, and soil nutrient dynamics in the context of biodiversity-ecosystem functioning (BEF) research. The BEF theory states that higher species richness can enhance ecosystem functioning. Thus, we hypothesize that rhizobacterial species richness will alter sorghum (Sorghum bicolor L.) growth, soil nutrient dynamics and interactions (antagonism or synergism) in a nutrient-poor greenhouse soil. Using six rhizobacterial species in a BEF experiment, we tested the impact of a species richness gradient (0, 1, 3, 5 or 6 species per community) on plant growth, nutrient assimilation, and soil nutrient dynamics via seed-inoculation. Our experiment included, one un-inoculated control, six rhizobacterial monoculture (Pseudomonas poae, Pseudomonas sp., Bacillus pumilus., Pantoea agglomerance., Microbacterium sp., and Serratia marcescens), and their nine mixture treatments in triplicate (48). Rhizobacterial species richness enhanced per pot above- or below-ground dry mass. However, the per plant growth and plant nutrient assimilation declined, most likely, due to microbial-driven competitive interactions among sorghum plants. But nevertheless, some rhizobacterial monoculture and mixture treatments improved per plant (shoot and root) growth and nutrient assimilation as well. Soil nutrient contents were mostly lower at higher plant-associated rhizobacterial diversity; among these, the soil Zn contents decreased significantly across the rhizobacterial diversity gradient. Rhizobacterial diversity promoted synergistic interactions among soil nutrients and improved root–soil interactions. Overall, our results suggest that a higher rhizobacterial diversity may enhance soil–plant interactions and total productivity under resource limited conditions.

尽管微生物影响植物生长，但在生物多样性生态系统功能 (BEF) 研究背景下，微生物多样性对植物健康权衡、种内相互作用和土壤养分动态的影响知之甚少。BEF 理论指出，更高的物种丰富度可以增强生态系统功能。因此，我们假设根际细菌物种丰富度会改变高粱（Sorghum bicolorL.) 营养贫乏的温室土壤中的生长、土壤养分动态和相互作用（拮抗或协同作用）。我们在 BEF 实验中使用六种根际细菌物种，通过种子接种测试了物种丰富度梯度（每个群落 0、1、3、5 或 6 个物种）对植物生长、养分同化和土壤养分动态的影响。我们的实验包括，一种未接种的对照，六种根际细菌单一培养（假单胞菌、假单胞菌、短小芽孢杆菌、泛菌、微杆菌和粘质沙雷氏菌），以及它们的九种混合物处理一式三份（48）。每个盆栽地上或地下干重均增加了根际细菌物种的丰富度。然而，单株生长和植物养分同化下降，很可能是由于高粱植物之间微生物驱动的竞争相互作用。但尽管如此，一些根际细菌单一栽培和混合处理也改善了单株（芽和根）的生长和养分吸收。与植物相关的根际细菌多样性较高时，土壤养分含量大多较低；其中，土壤锌含量在根际细菌多样性梯度上显着下降。根际细菌多样性促进了土壤养分之间的协同相互作用，并改善了根-土相互作用。总体，