Contour grass strips for soil erosion control on steep lands: a laboratory evaluation

The effectiveness of Festuca ovina and Poa pratensis as contour grass strips for erosion control was examined in a laboratory experiment for an erodible sandy loam soil on 21, 25 and 29 % slopes. No significant differences (P < 0.05) were observed in runoff between the plots with grass strips and bare soil but significant differences in soil loss were recorded. Both grasses reduced erosion in the early part of the simulated storms by ponding water behind the barrier, filtering sediment and causing deposition within the ponded area. The P pratensis barrier was less rigid and became flattened under submergence in the later part of the storms. Runoff flowed over the grass strip forming rills on the slope below, which then cut back and undermined the barrier. These barriers resulted in as much soil loss as bare soil towards the end of the storms on all three slopes. The F. ovina was effective in controlling erosion on the 21% and 25% slopes but not on the 29% slope.