Those who doubt the rationale of erosion control should refer to the history of the prairie states from 1933 to 1940. The area’s farmers were encouraged by foreign demand for wheat during World War II, so they planted wheat in larger and larger quantities. Unfortunately, the demand for wheat died down and the years of drought and extreme heat began. During that time, the area was ravaged by dust storms. Storms that picked up the topsoil formerly covered by buffalo grass, a native vegetation with eight to fourteen feet of root balls. The newly plowed land was no match for the infamous prairie winds, which picked up the loose earth and formed huge clouds of dirt standing as high as hundreds of feet in the air and spread for as much as two hundred miles across. The winds carried the soil at 40-60 miles per hour, during the worst of times.
Black Sunday
Black Sunday, April 14, 1935 was the date of the worst dust storm. Over 300 million tons of topsoil was estimated to have been displaced. The drought, poor soil conservation and wind erosion were the causes of property destruction, livestock lost due to suffocation and hundreds of human lives lost due to dust pneumonia. For seven years, the Great Plains suffered periodically from these wind erosion events. Fine particles of dirt was lifted into the air and carried for miles. Very fine dirt particles experienced “suspension” in the air. Larger particles skipped along the ground in a process called “saltation” and even larger particles would simply blow along the ground’s surface or “creep”. By one or all of these methods the topsoil would be moved when the wind picked up speed from an average of 11.4 mph to 40-60 mph as it did during dust storms.
The Great Plains
The events of this period made it clear that erosion control had to be implemented in the prairies states to reduce the occurrence of dust storms. The Great plains or the prairie states spans from eastern Montana across North Dakota to western Minnesota, encompassing South Dakota, Nebraska, Kansas, most of Iowa and Oklahoma, northwest Missouri, eastern Wyoming, Colorado and New Mexico and a large part of north Texas. Wind erosion techniques accomplish one of three things. At the surface of the soil, they reduce the wind force or they make the soil more resistant to the wind’s forces. Another option is to trap soil particles to reduce the abrasion of downwind soil surfaces.
Forms of Wind Erosion Control
Planting vegetation and trees is a very effective form of wind erosion control. This conservation practice traps moving soil particles, absorbs the force of the wind and helps with soil cohesion. To be most effective, crop rows should be planted perpendicular to the direction of the prevailing winds.
Surface Roughening
Another option is surface roughening and creating stable clods of earth to distribute along a plowed field. To create this uneven earth, different techniques may be used. This employs the use of crop residue, moist cow manure, soil tillage and artificial barriers made from straw rows, bamboo and willow fences, earthen banks, etc. Clodded soil absorbs more wind energy than a flat surface. If the earth is hard and ridged as well as clodded, it will absorb even more wind energy.
Wind Strip Cropping
Wind erosion control includes using cross wind strip cropping. The farmer plants his rows of crops perpendicular to the prevailing wind’s direction. The crops planted should alternate between crops that are susceptible to wind erosion and those that provide resistant cover, so that particles carried by the wind can easily be trapped as they blow across the planting field.
Barriers
Barriers, windbreaks or shelterbelts also reduce wind erosion. They reduce the wind speed by about ten times the height of the barrier of tall trees or bushes. These single or multiple rows of plantings serve many additional purposes. They provide a habitat for wildlife, protect crops and shelter livestock.
Residue and Tillage
Many wind erosion control techniques have been utilized over the decades. Laying down 2000-4000 pounds of crop residue per acre, such as corn stalks, hay or straw on top of the ground’s surface increases the possibility of the soil being trapped as particles blow along the ground. Emergency tillage can be used to create a rough, cloddy surface that’s ridged. It can reduce the wind’s velocity and trap windblown soil particles. Tilling should be done perpendicular to the prevailing wind’s direction. Even artificial barriers can be used to control wind erosion. Simply placing old tires on the planting field can help with wind erosion control. Many have resorted to spray-on adhesives or soil additives to protect the soil from wind erosion.
Americans learned a valuable lesson in the 1930’s. We learned that the earth must be used with preservation in mind. Erosion is a natural force that nature created to reshape the land. Normally, it carves out rolling hills, winding waterways and other beautiful and useful environments. When it is allowed to run havoc over the land because of our unwitting contribution, it leaves nothing but devastation and ruin like the wind erosion that caused the dust storms of the 1930’s.