The reduction of partitioned wind and water erosion by conservation agriculture

- Wind and water erosion can occur on the same field at different times.
- Quantifying wind erosion requires many years of sampling at many points in a field.
- Water erosion is quantified using sediment samplers and runoff measuring flumes.
- Total soil erosion is estimated from the radioisotopic method.
- Subtracting measured water erosion from total soil erosion yields wind erosion.

Soil loss due to wind and water erosion degrades the soil on-site and results in environmental problems due to deposition in off-site areas downstream and downwind of the source field. Wind and water erosion may both occur to varying extents particularly in semi-arid environments. Soil conservation strategies require information about the processes of soil redistribution to mitigate its impact. However, very few studies have partitioned soil erosion between contributions of wind and water. We quantified wind and water erosion on six graded terraces under a uniform crop rotation since 1949 and two tillage management practices begun in 1981. Detailed runoff and sediment yield data have been recorded on all the terraces since 1984. We used a stratified random sampling design to collect soil which were then bulked to form six composites for each terrace. From an adjacent undisturbed native prairie, soil cores were collected and composited similarly to provide a reference. The cores were composited by 15 cm layers in the terraces and, in the reference area, the upper 15 cm layer was subdivided into 5 cm layers and all were measured for 137Cs activity which was converted to 137Cs inventory. We then employed an established computer model that equates loss of 137Cs inventory with soil loss and direct measurement of water-borne sediment loss to estimate 30 year mean wind erosion losses on the terraces by tillage type. We found that no-till management reduced total soil loss by one-third compared with stubble mulch tillage, reduced water-borne sediment loss by about the same amount, and that for both tillage systems, wind erosion was responsible for about 75% of the total soil loss.