Effects of Ridge Length and Mulching on Erosion Control

Ridge and mulch in four different lengths and rates were investigated for the same area but for different periods of time under natural rainfall conditions to determine their effects on soil loss.The studies were carried out in four experimental plots,each 30m in length and 5m in width,on a gentle slope with 8% steepness(tangent)in the central part of Hiroshima Prefecture. The amounts of soil loss from each plot were collected in the sedimentation tanks set at the lower end of the slope,and measured by means of the spot level and bucket techniques.These eroded soil samples were analyzed to make clear their particle-size distribution as affected by the ridge lengths and the mulch rates.Application of mulch rates through the Universal Soil Loss Equation was demonstrated to gain their relation to the cropping and management factor C.The relation was expressed in the form of a modified equation and used to calculate the mulch rate necessary for controlling soil erosion under the given annual soil loss rate in the study area.