Wind Erosion in Western Queensland Australia

Chapter 2 – Land Erodibility Controlswind erosion are influenced by the nature of the cover. In particular, if the cover is prostrate(flat), or standing (Leys, 1991a).A few approaches have been taken to quantify the effects of vegetation cover on winderosion. These include: 1) studies to determine regression functions to describe therelationship between non-erodible roughness cover and erosion rates (soil loss); and 2)studies that seek to quantify the relationship between surface roughness and u *t .Prostrate non-erodible roughness elements reduce wind erosion by three mechanisms (Hagen,1996). These include: 1) increasing the static threshold at which entrainment begins (u *t ); 2)restricting the wind transport capacity by increasing the dynamic threshold for saltation; and3) increasing the distance required to attain transport capacity in short fields. In addition toproviding direct surface protection (cover), vegetation may trap creeping, saltating orsuspended particles, thereby reducing total potential soil loss relative to bare erodiblesurfaces.Research into the effects of prostrate vegetation cover has been dominated by wind tunneland field scale (10 3 m 2 ) experiments in cultivated environments. Early research sought toestablish threshold cover levels for prostrate plant litter and stubble that could be used tocontrol wind erosion in agricultural settings. For example, Chepil (1944) used laboratorywind tunnel experimentation with straw residue. He found a negative exponential relationshipbetween surface residue (weight) and soil erosion rates (Q) for any given wind velocity (U)and for a range of soil types. Siddoway et al. (1965) and Lyles and Allison (1981) foundsimilar relationships for Q with respect to various types, amounts and orientations (prostrateand standing) of stubble.Fryrear (1985) derived a negative exponential relationship between erosion rates (soil lossratio) and percentage soil cover. He defined the soil loss ratio (SLR) as the soil loss fromcovered soil to that of the soil in a bare condition, and relationships were determined fordowel and wheat stubble elements and a range of soil textures:SLR( Fc)= exp(2.27)55