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The overuse of agrochemicals for agricultural productivity to meet the global food demand of the rapidly growing human population is a great environmental threat, particularly for aquatic ecosystems. Being associated intimately with plant health, growth, and productivity, the plant microbiome is emerging as a promising environmentally friendly and sustainable resource for agricultural productivity. For the past decades, our understanding of the interactions between plants and microorganisms and our knowledge of how to improve the plant microbiome by using microbial inoculants has increased significantly. A better understanding of the impact of the plant microbiome on mineral resources will benefit plant and soil health. In this review, we highlight the importance of microbial inoculants and their interactions with mineral fertilizers in enhancing crop productivity, as well as current challenges.

Limited arable land area and deteriorating soil health in smallholder farmers’ fields of subtropical regions in China have led to an urgent demand for sustainable production practices with greater land productivity and nutrients use efficiency. A group of field experiments at three locations (Yaan, Lezhi and Renshou) in two consecutive years of 2012–2013 were conducted to study crop production and nutrients recovery of maize (Zea mays L.) and soybean (Glycine max (L.) Merr.) in monocropping and additive relay intercropping systems. The results showed that the total crop yields of the 2:2 maize-to-soybean wide-narrow row spacing planting pattern (RIwn) were significantly higher than that of the 1:1 maize-to-soybean equal row spacing planting pattern (RIe), and the average land equivalent ratios (LER) of the grain yield were 1.79 and 1.49 for the RIwn and RIe, respectively. The nitrogen (N), phosphorus (P) and potassium (K) recovery efficiency calculated by the ratios of crop nutrients removed and fertilizer input indicated that the RIwn had a higher nutrients recovery than the RIe due to proper spacing between maize and soybean rows and higher soybean yield in RIwn. In terms of the amount of fertilizer applied, based on this experiment, P should be reduced in maize plantings and increased in soybean plantings to maintain the balance of soil P. Considering the higher temperatures during the soybean vegetative growth phase, N fertilizer inputs should be controlled to prevent excessive soybean growth. In addition, excess K was taken up in the crop biomass, maybe the straw should be returned to the field to maintain soil K fertility sustainable for the long term.

Agricultural activities and agro-inputs, particularly chemical fertilizers, farmyard manure, pesticide, sewage sludge, plastic mulch, irrigation, etc., are the primary source of pollutants in farmlands. Agricultural land degradation has become a major concern as it poses a threat to crop productivity. In recent years, microbial-assisted phytoremediation has gained much attention as a promising in situ remediation technology for cleaning polluted soils. Several beneficial rhizobacteria and endophytes facilitate phytoremediation by stimulating innate plant growth-promoting traits such as the production of siderophores, phytohormones, and chelators in addition to their ability to biodegrade contaminants and enhance their removal. Current studies on microbial mediated phytoremediation are demonstrating significant remediation potential. However, there are several challenges in the field that restrict the remediation process. Here we highlight the specific traits, mechanisms, roles, advantages, and problems associated with microbial-assisted phytoremediation.

The solubilization and mineralization of phosphorus by phosphate-solubilizing bacteria (PSB) is one of the most important bacterial physiological characteristics in the soil biogeochemical cycle. Through the isolation and screening of microorganisms in the rhizosphere soil of intercropped soybean in Ya’an, Renshou and Chongzhou, 9 PSBs with high phosphorus solubilizing ability were identified. It mainly belongs to Bacillus and Pseudomonas. The phosphate solubility of Bacillus aryabhattai B8W22 is as high as 388.62 µg·mL-1. The physiological and biochemical characteristics of each strain showed that it can secrete organic acids such as formic acid, acetic acid lactic acid and pyruvic acid. In addition, all strains can produce indole acetic acid and siderophores that promote plant growth. Seed germination experiments also showed that the phosphorus solubilizing bacteria isolated in this research have a certain ability to promote plant growth.IMPRTANCEBacillus aryabhattai from rhizosphere soil of intercropped soybean has high phosphate-solubilizing ability, could produce indole acetic acid and siderophores that promote plant growth, and are of great significance in reducing the application of chemical phosphate fertilizers and promoting sustainable agricultural development.