Abstract: In order to construct a set of technical system that could effectively improve the structure of red soil and improve the efficiency of vegetation restoration, the effects of biochar (2.0%) and polyacrylamide (PAM, 0.5%) addition on soil structure, physiology and growth of Paspalum wettsteinii were studied in red soil of southern China. The results showed that, compared with the control without soil conditioner(CK), the saturated hydraulic conductivity of soil treated with PAM increased by 18.4%, while that of the mixed treatment of PAM and biochar decreased by 42.4%. Single application of PAM or biochar could not increase the capillary water retention capacity and field water retention capacity of red soil. The mixed application of PAM and biochar significantly increased the capillary water retention capacity, field water retention capacity and capillary porosity of red soil. Under drought conditions, compared with CK, the mixed application of PAM and biochar significantly reduced the malondialdehyde content in the leaves of Paspalum wettsteinii, and significantly increased the water content in the leaves and the plant height of Paspalum wettsteinii. In summary, the addition of 2.0% biochar and 0.5% PAM showed the best effect in improving the structure of red soil and promoting the growth of Paspalum wettsteinii.

Key words: red soil, drought stress, soil conditioner, biochar, polyacrylamide, water retention characteristics, physiological characteristics, Paspalum wettsteinii Hackel, drought resistance characteristics