Reducing Soil Loss During A Drought
March 31, 2009 Growers in drought-stricken areas of California opting not to plant crops this year are being advised to leave their fields in “roughed up” condition to prevent soil loss due to wind erosion. Large portions of the state are currently classified by the National Drought Mitigation Center at the University of Nebraska as experiencing severe or extreme drought. The potential for soil loss due to wind erosion in these areas could be as great as 250 tons per acre a year. Loss of irrigation water could result in vast acreages of farmland being taken out of production, resulting in many acres of bare soil.
Abandoned, bare fields are subject to severe wind erosion according to Rita Bickel, an agronomist with the Natural Resources Conservation Service in Davis, CA. “Fields continually subjected to erosion may result in land that is incapable of returning to cropping or vegetative systems at a later date,” she says. Bickel says not only could vast amounts of precious topsoil be lost, but air quality will be impacted as well, with blowing soil impairing vision on roads and highways. She advises growers to take steps now to create surface roughing such as building furrows or ridges. These will absorb and deflect part of the wind energy and trap drifting soil particles.
“Vegetation, or vegetative residue, is the best protection for prevention of erosion from wind or rain when fields are left fallow,” she says. “After the last crop is harvested, it is best to save as much of the remaining crop residue, stubble, or ridges as possible. Even weeds can be sprayed in place and left as cover. Soil will be somewhat protected if there is at least 30% cover on the surface.”
Tillage with an implement, such as a lister, running perpendicular to wind direction, will form ridges and clods that will provide some protection for soil. This is most successful with soil that has some texture; sandy soils won’t hold the shape of clods and furrows as well as soils that contain at least some clay.
Additional steps growers can take to prevent soil loss include compacting unpaved farm roads, avoiding plowing noxious weeds until adequate moisture is present to allow stable clods to form, establishing permanent vegetation on cropland being converted to other uses, and stabilizing equipment lots not protected by windbreaks or cover vegetation. “When leaving land fallow,” Bickel concludes, “the key to protecting soil resources is to provide as much cover and roughness as possible.”
Source: USDA – Natural Resources Conservation Service
