|Main authors:||Abdallah Alaoui and Gudrun Schwilch
|Source document:||Alaoui, A. and Schwilch, G. (2016) Soil quality and agricultural management practices inventory at case study sites. iSQAPER Report 28 pp|
The susceptibility of a soil to wind erosion depends on factors including soil moisture and wind velocity, surface roughness, organic matter content and particle size. Soils that have low volumes of organic matter and have lost their structure through compaction and over-cultivation are pulverised to dust on further cultivation, making them vulnerable to wind erosion if un-protected. Wind erosion reduces the productive potential of soils through nutrient losses, lower available water-holding capacity and reduced rooting volume and depth.
The water erodibility of soil on sloping ground is governed by factors including the amount and intensity of rainfall, the degree of slope, and the soil infiltration rate and permeability. The latter two are governed by soil structure and texture.
- Assess, based on knowledge of the area or visual observations during the season, whether the amount of wind erosion during and after cultivation has become a concern.
- Take into account the size of the dust plume or clouds raised during or after cultivation, and whether the material stays within the field, within the farm, or is blown into the surrounding area.
- Determine the severity of water erosion by augering or digging holes to compare the difference in topsoil depths between the crest and the bottom of the slope, and by observing the amount of sheet and rill erosion, as well as sedimentation into surrounding drains and streams.
Good condition: Score 2
Wind erosion is not a concern: only small dust plumes emanate from the cultivator on windy days. Most wind-eroded material is contained within the field. Water erosion is not a concern as there is only a little rill and sheet erosion. Topsoil depths in valley areas are <15cm deeper than on crests. Deal with water erosion and wind erosion separately if both have occurred. Reduce the score by one point.
Moderate condition: Score 1
Wind erosion is of moderate concern where significant dust plumes can emanate from the cultivator on windy days. A considerable amount of material is blown off the field, but is contained within the farm area. Water erosion is of a moderate concern with a significant amount of rilling and sheet erosion. Topsoil depths in valley areas are 15-30cm greater than on crests and sediment input into drains/streams may be significant.
Poor condition: Score 0
Wind erosion is a major concern. Large dust clouds can occur when cultivating on windy days. A substantial amount of topsoil can be lost from the field and deposited elsewhere in the district. Water erosion is a major concern, with severe rilling and sheet erosion occurring. Topsoils in valley areas are more than 30cm deeper than on the crests and sediment put into drains/streams may be high.