By Paul Jasa
Figure 1. Planting down the old row and leaving the residue attached can help reduce the potential for wind erosion. Residue movers should not be used as they detach residue, allowing it to be moved by wind or water.
Soil erosion by wind becomes a serious problem when natural vegetation is removed or depleted. It can occur anywhere when vegetation and climatic conditions are conducive. These conditions exist when
- the soil is loose, dry, and finely granulated;
- the soil surface is reasonably smooth and vegetative cover is nonexistent or sparse;
- there are large fields with no obstructions to reduce the force of the wind; and
- the wind is sufficiently strong to initiate soil movement (Beasley, et. al. 1984).
While many people think wind erosion is only a problem in arid regions out west, any time there is dry, bare, unprotected soil, wind erosion can occur. Tillage, historically used to prepare fields for planting, creates soil conditions susceptible to wind erosion by breaking down soil aggregation, destroying residue, and drying the soil. Without moisture to hold the particles together, wind can detach soil particles and transport them across the fields.
- Large particles move by saltation, rolling along the surface detaching more soil particles.
- Smaller particles move by surface creep, much like a sand dune, but on a much smaller scale.
- The smallest particles move by suspension, meaning they are carried along by the wind, forming dust clouds in the sky.
Figure 1. Historically, tillage was performed to roughen the soil surface to reduce soil particle detachment by wind. While effective for a short time, the tillage destroyed aggregate stability, dried the soil, and actually made the soil more susceptible to wind erosion as the roughened surface broke down.
Figure 2. Vertical tillage implements detach the crop residue, making it susceptible to movement by wind and water. It’s best to leave residues anchored and attached to reduce erosion and minimize residue movement.
Reducing Wind Erosion
The best way to reduce wind erosion is to keep the wind off the soil surface by covering the soil surface. Growing vegetation, either cash crops or cover crops, protects the soil and keeps the winds higher off the surface. Standing crop residues function the same way. Flattened crop residues are more effective at reducing soil erosion by water by absorbing raindrop impact. The key to reducing erosion is to absorb the energy of the wind or water before it can detach soil particles. Windbreaks and other barriers are also effective at keeping the wind off the soil surface and reducing soil particle detachment, but these practices may take land out of crop production.
Once soil particles are detached, their movement needs to be limited by increasing deposition. Any time the wind (or flowing water) slows down, it loses the ability to carry as much soil. For instance, surface residues and/or growing vegetation greatly reduce soil movement by saltation or creep by creating barriers to particle movement. Historically, tillage was used to roughen the soil surface to do the same thing. However, the tillage treatment was extremely temporary as the wind erosion smoothed out the tilled soil surface. The tillage actually broke down more soil aggregates and buried more residue, making the soil more susceptible to future erosion events.
Windbreaks and other barriers are effective at decreasing soil particle transport by causing deposition behind the barrier. While this is more easily seen in the snowdrifts that form behind a snow fence in winter, the same thing happens with soil in a wind erosion event. The deposition usually occurs in a distance behind the barrier roughly equal to twice the barrier height. In addition the barrier reduces the wind velocity beyond it to effectively reduce soil particle detachment for a distance of about five to ten times the barrier height. Thus, windbreaks with 50-foot tall trees would “protect” the soil for about 500 feet downwind from them, not very far across a quarter section of land.
Preventing Erosion
When it comes to wind erosion control, prevention is far more effective than the cure (emergency treatments once wind erosion is occurring). The soil surface should be kept covered with growing vegetation or standing, attached residues. While many producers practice no-till in Nebraska, those who run residue movers on their planters risk wind erosion problems because they detach their residues. Likewise, stalk shredding and vertical tillage increase the chance of wind erosion problems as these operations also detach crop residues. In areas where wind erosion occurs regularly, producers should no-till between the rows of standing residue and let the residue keep the wind off the soil surface. This standing residue will also help keep any surface residue from being moved by the wind. In areas where raindrop impact and water erosion are more of a concern, producers should plant down the old row, without residue movers, so that the residue remains attached and protects the row.
Emergency treatments to reduce wind erosion once it is occurring are fairly limited. Tillage to roughen the soil surface was historically used but actually added to the problem with future wind events. Roughening the soil surface with a drill seeding a cover crop may be more effective if the cover crop can become established, as the canopy of the cover crop will protect the soil as the winds smooth out the roughened surface. This roughening with a drill while seeding a cover crop could be done on widely spaced passes across the field, perpendicular to the wind, and repeated in the spaces between the passes during future wind events. This would provide the roughened soil surface historically created with tillage as well as add vegetation to protect the surface.
If center pivot irrigation is available, producers with active wind erosion should irrigate the dry soil surface to reduce it from blowing. Wet soil surfaces are less likely to blow because of the moisture and the cohesion between soil particles. In a similar way, the cohesion between soil particles on a crusted soil surface may reduce wind erosion problems by holding them together. Producers should not till a soil to eliminate a crust unless the seedlings are having problems emerging through the crust. Even then, the crust should only be broken up over the row, not in the middles between the rows. Again, if center pivot irrigation is available, it would be more effective to irrigate to soften the crust to aid seedling emergence.
Take-Home Point
The potential for wind erosion is reduced any time the soil surface is covered. Likewise, the potential is reduced if the soil surface is kept moist. Crop residue and growing vegetation keep the wind off the soil surface and reduce soil moisture evaporation. Tillage destroys soil cover and dries the soil and should be avoided in areas prone to wind erosion. Standing, attached residue is the most effective practice to reduce wind erosion so planting equipment should be operated to minimize residue detachment.