Many Vertisols in Tigray, Ethiopia, typically carry a discontinuous rock fragment (RF, size 0.5->40 . 10(-2) in) cover with 10 m(-2). Such RF mulches are of agricultural and environmental significance because they influence the water balance to 100 RFs Such RF mulches are of a. in the underlying soils and the crop yield. Natural RF concentrations are mostly considered as eolian or hydraulic lag deposits, or as the result of lateral transport over the soil surface from a rock Outcrop, upslope. In cultivated areas R-F mulches can develop by tillage.