Hydroxyapatite as a passivator for safe wheat production and its impacts on soil microbial communities in a Cd-contaminated alkaline soil

The remediation of Cd-contaminated alkaline soil plays a critical role in safe wheat production. In this study, hydroxyapatite (HAP), a functional environmental remediation material, was selected to investigate the effects of HAP on cadmium accumulation in winter wheat (Triticum aestivum L.), Cd bioavailability in alkaline soil moderately polluted with Cd (2.46 mg kg-1) and the soil bacterial community via pot experiments. The results showed HAP effectively inhibited Cd accumulation in the grains of two investigated wheat cultivars by hindering root uptake. The Cd concentrations decreased by 49.9–81.9%, and 35.7–92.4% in the grains of Zhoumai-30 and Zhengmai-7698, respectively. HAP increased the soil pH and reduced the bioavailability of Cd. 16S rRNA sequencing analysis indicated that the changes of soil physicochemical properties changed the diversity and composition of the bacterial community by increasing the relative abundance of beneficial soil bacteria. These results demonstrated the application of 2.5% HAP combined with planting Zhengmai-7698 treatment was a potential remediation method for safe wheat production, and also benefited soil P and N cycling by increasing the relative abundance of beneficial bacteria. The good performance of HAP in inhabiting Cd accumulation in wheat grains indicated it is a promising material for safe wheat production.