Effectiveness of Grass Strips as Barrier Against Runoff and Soil Loss in Jijiga Area, Northern Part of Somali Region, Ethiopia

Abstract

                In this study, sixteen standard runoff plots with a dimension of 22.13 × 1.8 m each were constructed in a contour on a cultivated land with slope gradient of 9 % in Jijiga area of the northern part of Somali region of Ethiopia at the end of the year 2003. To evaluate the effectiveness of grass strips as barrier against the runoff and soil loss, an experiment was laid out in randomized complete block design with four treatments by four replicates on the constructed sixteen runoff plots. The treatments were one control-without grass strip and three different grass strips of 1 m wide each. The grass strips, namely desho, setaria and vetiver were established at a spacing of 15 cm within a row on the lower end runoff plots. All the runoff and soil loss from the treatments were measured during 38 storm events in the years 2004 and 2005. The depth of sediment deposition along the strips and the growth rate of strips were also measured. In both 2004 and 2005 study years, the three grass treatments showed significantly lower annual runoff and soil loss results compared to the control treatment. However, the lowest runoff and soil loss were recorded from the vetiver grass. This was because of its faster growth rate than both the desho and setaria grass strips. The depositions of sediment along the three grass strip treatments were significantly higher than that of the control section, suggesting that three grass strips had the potential to cause terracing. However, the preference should be for the vetiver grass because it formed terraces much quicker than both the desho and setaria grass strips.

                 In general, even though the three grasses could be used as barrier against runoff and soil loss, and had potential to cause terrace formation on gentle slope, it was however recommended that they should be rated as: vetiver>desho>setaria in accordance with their relative effectiveness.