Reduce Soil Loss from the Field
Soil loss from the field can be reduced by:
- Decreasing erosion
- Trapping eroded particles in filter strips within or at the edge of a field
Decreasing erosion
Much of the P that moves off the land and into water is in the form of soil particles. The P may be part of an organic matter particle from plant residue or manure, or it may be held in complicated aluminum, iron, and calcium compounds.
For centuries we have been trying to decrease erosion, and many effective techniques have been developed, including:
- Reduced tillage - minimum tillage
- Contour tillage
- Increasing residue on the soil surface
- Cover crops
- Strip-cropping, terraces
- Maintaining a perennial grass cover (managed grazing)
Depending on your location, any one of these or a combination of these management changes can decrease soil loss and thus lower the particulate PI. For example, established no-till corn may erode only 10-20% as much soil as the same field would if it were moldboard plowed.
In addition, establishing grassed waterways is an important practice to reduce soil loss wherever recurring gullies tend to form. However, this practice is already required under Wisconsin's 590 Nutrient Management Standard, so it will not affect the PI.
For further information on erosion-control techniques, contact:
- Wisconsin specialist Richard P. Wolkowski, Extension Soils Science
- Your county Natural Resource Conservation Service or Land Conservation Department office.
Trap Eroded Particles in Filters Strips or Buffers
Once soil has been eroded from a field and reaches the edge of the field, it may go directly into a concentrated flow channel (ditch or stream), or it may pass through an additional distance of vegetated land.
When water moving in a thin film (sheet flow) moves into a vegetated area, there are many opportunities for P removal. The stems and residue of the vegetation will slow the velocity of the water, allowing many of the larger particles to settle out. Some particles will actually be filtered out by being trapped between leaves of grass, for instance.
The greatest benefit of vegetated filter strips can be the increased infiltration capacity they provide. Of course this depends on slope, vegetation, how long the water resides on the site, etc. Filter strips need to be maintained so that they continue to function effectively. Otherwise, they can fill with sediments, vegetation may die back, or "short circuits"-channels through them-can develop.
For more information contact your county Natural Resource Conservation Service or Land Conservation Department office.
Note: The current version of the P Index in SNAP-plus does not include buffer strips. That option will be available in mid-2006.
Good web sites for more information:
Buffer Strips: Common Sense Conservation. USDA-NRCS
BufferNotes web publication - USDA
