Soil Indigenous Microbes Protect Maize Plants in Arsenic-Contaminated Soils

Abstract

Arsenic (As) pollution of agricultural soils causes adverse effects on crop development and can increase As uptake by humans. We performed a greenhouse pot experiment with maize (Zea mays L.). Three soil treatments with varying microbial disturbance were designed: native soil, sterilized soil, and sterilized soil reconditioned with soil microbes. The three soil treatments were intersected with three levels of As in soils (0, 100 and 200 mg kg− 1 spiked As). The effect of As on the microbial community was only investigated in the native soil, while the combined effect of As and microbial disturbance was investigated in all treatments. Plant height, fresh biomass, BBCH-scale, leaf numbers, leaf chlorophyll content and leaf damage were recorded. We also analyzed the microbial community composition in the soil and in maize and the activities of soil enzymes (N-β-acetylglucosaminidase, acid phosphatase, β-glucosidase, β-xylosidase and cellobiohydrolase). In the native soil, As increased soil bacterial alpha diversity but did not consistently alter microbial community composition or the activities of the five measured soil enzymes. Root, leaf and grain microbiomes were little impacted by As. High As levels alone did not reduce most maize health parameters, except for leaf damage scale. However, the combination of soil sterilization and As reduced plant height and leaf chlorophyll content, while enhancing leaf damage scale. The effect of soil sterilization was partly weekend by microbial reconditioning. In summary, soil indigenous microbes are largely resilient to high As levels and help protect maize against As stress.