This time of year the waters of the Palouse River in eastern Washington rarely run pure and clear. Instead, they are brown, choked with about 3 million tons of valuable topsoil destined to wash downstream into the Snake and Columbia Rivers and eventually out to sea.
This topsoil comes from the Palouse region of southeastern Washington, one of the nation's most productive and beautiful farming areas. More than a tenth of the nation's wheat and nearly all of its peas and lentils are grown on the distinctive rolling hills of the Palouse.
It took thousands of years to deposit the wind-blown loamy soil across the Palouse, in places nearly 200 feet deep. It has taken less than a century of cultivation to remove enough of this topsoil to cover an area equal to eight city blocks, eight stories deep.
Since 1934, nearly three-fourths of a ton of topsoil has been lost for every bushel of wheat produced in the Palouse basin, According to a 1978 survey by the US Soil and Conservation Service.
Although the soil conservation service considers the Palouse one of the most serious erosion areas in the United States, it is not alone. Almost equally severe erosion problems can be found in Aroostook County, Maine; in southeastern Idaho; in the Blackland Prairie area of central Texas, and along parts of the southern Mississippi Valley, to name a few.
On the average, the nation's farmlands are losing five to nine tons of topsoil per acre a year, says Dennis Roe of the soil conservation office here. An erosion rate of four to five tons is considered acceptable because the eroded soil still can be replaced through natural means, he said.
In the Palouse, however, soil erosion is occuring at an average rate of 14 tons anr acre a year, with rates of 20 to 30 tons common. On some steeper slopes, the erosion ranges from 100 to 200 tons an acre.
"Old-timers can remember when areas without topsoil were pretty spotty," Mr. Roe said. "Now in some fields all the slope has subsoil exposed," he said. He estimates there are areas in the Central Palouse where at least 20 percent of the topsoil has been lost, leaving behind the less productive subsoils.
The Palouse is among the most unique farming areas in the US. Despite its northern latitude, it has an almost Mediterranean climate. It receives most of its rainfall from late November through March. The silty, loamy soil holds moisture well, allowing farmers to produce as many as 50 bushels of wheat per acre from dryland farming.
Compared with other parts of the country, farming came fairly late to the Palouse. It wasn't until nearly the end of the 19th century that the region was finally settled and farmed.
Farming techniques introduced then are the main causes of the erosion problems today, Roe said. Chief among them is the common practice of leaving half of the fields fallow each summer in order to catch and store enough moisture from the previous winter.
This allows for good yields without irrigation, but it also allows more erosion because nothing is planted on the land to hold the soil in place. Erosion rates on summer fallow fields average 25 to 30 percent higher than non-fallow fields, the conservation service estimates.
In recent years the erosion problem has been compounded by the fact that land once planted in grass has been turned to cash crops as the federal government ended its set-aside program.
Farmers can do little about the weather or the kind of soil or the steepness of the land they farm, but they can do something about the way they farm, Roe says. He has had some success encouraging Palouse farmers to reduce the number of acres in summer fallow by offering more economical and soil conserving crop rotation options.
So as not to exhaust the soil, he encourages a three-year rotation pattern of winter wheat, spring barley, and then leaving the land fallow. Some farmers are planting peas during the third year.
The conservation service also is trying with some success to encourage farmers to change their tillage habits to leave more stubble on the ground or to divide the slope into two or more crops.
The service estimates the soil erosion in the Palouse can be reduced from 40 to 60 percent by simple conservation techniques of this kind without seriously affecting farm income.
Erosion could be reduced as much as 80 percent through maximum application of soil conservation and by retiring some of the steeper slopes, but this would cost more than $29 million in reduced productivity and increased operating costs.
"It's been likened to a new dust bowl, but it is not that serious," Roe said. "You have to give the farmers credit. They've been innovative in coming up with new techniques."