Microbial biomass and enzyme activity of the rhizosphere soil under different grafted Xanthoceras sorbifolia cultivars

Xanthoceras sorbifolia is an important plant species for landscaping and energy use, but mostly grown in wild or semi-wild environment with low yield. Grafting can enhance crop yield and improve stress tolerance properties, and can also influence rhizosphere soil properties. Although lots of grafting techniques in X. sorbifolia have been reported so far, the impacts of grafting on soil properties have not been well documented. In order to understand whether grafting could improve soil biological properties or not, we assessed microbial biomasses and enzyme activities of rhizosphere soils under non-grafting and grafting treatments. X. sorbifolia scions of four different cultivars, i.e. wild white flower cultivar from Fuxin (LFB), Liaoning Province of northeastern China; wild white flower cultivar from Jianping (LJB), Liaoning Province; wild red flower cultivar from Chifeng (NCH), Inner Mongolia of northern China; and planted red flower seedling (NSH) from Inner Mongolia were grafted onto X. sorbifolia rootstock from Changping, Beijing, respectively. Compared with the non-grafted (CK) cultivar, the microbial biomass C of the rhizosphere soils under LFB, LJB, NCH and NSH were significantly increased by 62%,45%,91% and 40%, whereas the microbial biomass N of the rhizosphere soils under NCH, LFB and NSH were significantly increased by 140%, 107% and 56%, respectively. In contrast with CK, the activities of β-glucosidase, glucosaminidase, leucine amino peptidase and phosphatases of rhizosphere soils under NCH, LFB and NSH were significantly increased, whereas the activity of phenol oxidase was markedly decreased. A significantly positive relationship was observed between the change of activities of glucosidase, glucosaminidase as well as leucine amino peptidase and microbial biomass, dissolved soil carbon and dissolved organic soil nitrogen. In summary, the white-flowered scions from Fuxin, Liaoning and red-flowered ones from Chifeng, Inner Mongolia grafted onto the rootstock from Changping, Beijing could improve microbial biomass and enzyme activities of rhizosphere soils.