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One of the greatest threats to American agriculture is not stiff overseas competition for our farm export markets, low commodity prices, increasing operating costs, or bureaucracy that threaten to strangle farm enterprise.

It is erosion.Nearly 1.5 million acres of land are being removed from agricultural production every year because of erosion either from wind or water and of the cropland remaining 421 million acres nearly half of it is eroding too fast to maintain long-term productivity.

America has already lost a great deal of land to poor farming methods that have robbed the soil of its nutrients, and is continually losing more of its farm land to subdivisions and highways and to business and industrial developments.

In addition, salinity affects 10 percent of cropland and pastureland 57 million acres.

We don't have so much rich top soil that we can afford to throw it away. But that is what is happening across America. And not only does the land suffer, but eroded top soil dirties our creeks and our sources of drinking water, increasing the cost of providing water to cities. In many areas, dust from wind-eroded land creates air quality problems.

Scientists say an acceptable rate of erosion is one to five tons per acre per year. They consider erosion tolerable when eroded topsoil can be replenished through natural processes.

When we talk about highly eroded land, we're talking about erosion that is greater than five tons an acre per year. Erosion rates exceed tolerable levels on nearly 300 million acres of cropland, pastureland, forest land, rangeland, and other rural lands.

About 60 million acres 14 percent of the nation's cropland is eroding at rates exceeding three times the tolerable level.

The estimated average annual erosion from the nation's farmland and other non-federal lands is more than 6.5 billion tons of soil. Of this total, about 1.1 billion tons erode from streambanks, gullies, construction sites, roads, and roadsides. The greatest soil losses are on cropland, which is sustaining an estimated annual soil loss of 3 billion tons.

Anyone who doubts the power of wind and water to carve away the land should visit Utah's Canyonlands, the Grand Canyon or any of America's famous caves. Many of these areas show what nature can do to solid rock. When one considers the pliability of loose soil, the power of erosion on cropland is even more evident.

Many practical systems are available for controlling soil erosion, including conservation tillage, where residue from a previous crop is left in the field, and no till, which leaves almost all of the previous crop residue as mulch on the soil surface year round. These methods, where feasible, reduce erosion to negligible rates.

Farmers need to use these methods if soil is to be saved. Contractors need to learn how they can save the soil on and near their construction sites.

Strip mining companies that claim the earth's minerals and raw materials, such as sand and gravel, need to utilize conservation methods throughout their digging operations and afterward. They should reforest and restore their sites.

A host of conservation programs are available from the U.S. Department of Agriculture, the Soil Conservation Service and the Agricultural Stabilization and Conservation Service, including not only technical help but financial incentives.

School teachers can find an abundant amount of information to help their students learn about erosion and soil conservation from the Utah Department of Agriculture's Agriculture in the Classroom program.

We have a tendency to take something as common as topsoil for granted. The economic and cultural disaster that erosion caused farmers in the Oklahoma Dust Bowl in the 1930s is just one example of what happens when people do not respect the soil.

Yet, we are losing more soil now than we did during the Dust Bowl years. Erosion rates will be even worse if export demands pull more marginal land into production. An Iowa State University study shows soil erosion losses in the eastern Corn Belt could jump 50 percent above the level of just 15 years ago and in the western Corn Belt they could increase by 80 percent.