Research on reducing surface runoff and erosion by using vegetation method has been widely carried out. But the using of grasses plants to control erosion and landslide was not yet widely done, especially the effect of plant root parameters on reducing surface runoff and erosion. A research was carried out on volcanic soil in Experimental Station, Agriculture Faculty, Andalas University. This study was carried out from April 2018 to November 2018. It uses a 15 m x 2 m plots that was limited by

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... rick concrete on 3 sides and the other side was used for measuring runoff and soil erosion. This experiment consisted of 4 treatments with 3 replications. The experimental units were arranged to according to a completely randomized design (CRD). Data were analyzed the variance using F test at 5 % level of significance and then continued using the Least Significance difference (LSD 0.05 if F calculated > F table. The treatments were ; A = Vetiver + Simple terrace, B = Vetiver + Napier grass, C = vetiver + King grass, D = King grass + Napier grass. Observations were carried out on surface runoff, soil erosion, soil physical properties , soil shear strength, and root characteristics . Root characteristics observations using the Mwango et al (2014) method. Their parameters were root diameter, root density, root length density, root area ratio, and relative soil particles detachment rate. The field experimental results showed that combination of Napier and King grass (D) are better than another treatment to decrease surface flow and soil erosions. Between King grass + Napier grass (D), vetiver + Napier grass (B) and vetiver + King grass (C) treatments were not significantly different, exceptly with Vetiver grass + simple terrace. This statement also contribute by soil strength, and root properties at 0-30 cm depth.