Root characteristics of Cynodon dactylis and Trifolium repens and their effect on shear performance of purple soilin barren hillside

To investigate the soil reinforcement of grass roots on purple soil on barren hillsides and the factors affecting it, purple soil under the environment was assessed via an experiment with three treatments: A blank control and soil under Cynodon dactylon and Trifolium repens. After eight months, basic physical and chemical properties, root parameters, and soil shear strength were measured by conventional methods, the root analysis system (WinRHIZO(Pro. 2004c)) and strain controlled direct shear apparatus. The root parameters of C. dactylon were better than those of T. repens; root diameter of C. dactylon was significantly higher than that of T. repens (d≤0.2 mm; P<0.05). C. dactylon was more effective than T. repens in improving soil physical and chemical properties. Both kinds of grass effectively improved the shear performance of the root-soil system. Compared with the blank control, the internal friction angle (φ) and cohesion (c) of soil under C. dactylon and T. repens were higher by 10.37%, 66.36%, and 1.14%, 34.22%, respectively, and the shear performance of soil under C. dactylon was better than that of soil under T. repens. Soil bulk density, total porosity, capillary porosity, and root length density (RLD) were the key indexes affecting the shear performance of the root-soil system, and d ≤ 0.2 mm was the critical diameter class affecting shear performance.