The North Pacific Valleys

H. B. Cheney.

Several unusual characteristics influence soil management in the North Pacific valleys.

They are: Land forms; abundant, low-intensity winter rainfall, but summer drought; a narrow range in temperature, with relatively warm winters and cool summers; a long frost-free period; moderately leached to highly leached, acid soils; abundant water for irrigation and power; a large number of adapted crops; concentration of crop production in the valleys; and rapid expansion of urban population.

The relief is varied and strong. The crest of the Cascade Mountains, an effective boundary on the east, averages 5 thousand to 8 thousand feet. Many peaks, most of them of volcanic origin, are higher.

Lower mountains occur along the entire coast. Except for the Olympic Mountains in northwestern Washington, they are less than 4 thousand feet.

The Willamette-Cowlitz-Puget lowlands, between the coastal mountains and the Cascade Range, extend 350 miles from west-central Oregon to Canada and are 20 to 70 miles wide. They are primarily stream valleys that contain alluvial terraces and (in the Puget lowland) glaciofluvial gravel. Many smaller valleys and alluvial terraces occur near the coast and along the Rogue and Umpqua Rivers in Oregon.

The marine influence predominates, but the coastal mountains and the Cascade Range modify it.

The highest precipitation in agricultural areas occurs along the coast, where the annual average is 50 to 100 inches. Precipitation is even higher in the coastal mountains, but it drops sharply in the valleys east of them. The average precipitation near Puget Sound is 20 to 40 inches a year; in the Willamette-Cowlitz Valleys, 35 to 50 inches and in the Rogue and Umpqua Valleys, 16 to 30 inches.

Typically, half of the precipitation falls in winter. Less than 5 percent falls in July and August. Low-intensity rainfall usually falls 16 to 20 days a month in winter, but a total of 0.5 to 1.5 inches is typical in July and August.

Temperatures are remarkably uniform in the farming areas. The average January temperatures are 35 to 45 F. The average July temperatures are 55 to 70 . The small change from winter to summer reflects marine influence.

The frost-free period is more than 200 days in most of the agricultural areas. The Rogue River Valley and some localities in the interior valleys have a shorter growing season.

The soils along the coast are highly acid and low in bases. The soils in the interior valleys are slightly to strongly acid. Soils formed from recent alluvium generally are less acid than soils in the nearby uplands.

Trees notably Douglas-fir are the natural vegetation of the region. In the areas of higher rainfall in the mountains and along the coast, hemlock, western redcedar, and alder also occur. Redwood grows along the coast in California. In the areas of lower rainfall, the Oregon white oak, ponderosa pine, sugar pine, California black oak, madrone, grasses, manzanita, and poison-oak are typical of the natural vegetation. Grasses, along with shrubs and trees, occur naturally on many of the alluvial soils.

Only 19 percent of the total land area is in farms. About one-third of the 6.6 million acres in farms is cropland. The rest is pasture and woodland.

Practically all cultivated land along the coast is in forage crops. The remainder of the region grows many crops, among them a host of horticultural crops, small grains, and grass and legumes for seed.

An abundance of water resources provide water for irrigation, power, and navigation.

The use of sprinkler irrigation has increased rapidly since 1945. Additional storage reservoirs have been planned to provide the water needed in summer.

The economy is dominated by forestry and agriculture and the processing and manufacturing industries that are associated with them.

Population densities both urban and rural are high in the Puget Sound and Willamette Valley zones.

The increasing population has several effects on soil-management programs. Local markets for dairy and poultry products, fruits, vegetables, and nuts have increased. Many farms are small and have intensive operations. The utilization of additional land for urban and other nonagricultural purposes has heightened the pressure on the remaining agricultural land and has caused some of the best farmland to be shifted to other uses.

AMONG THE COMMON soil-management problems are inadequate drainage and flooding, because much of the farm production is on alluvial soils.

Total rainfall is adequate, except in the southern interior valleys, but summer drought limits production of many crops throughout the region.

Soil acidity is a problem in many places. All the soils are acid, but some are not excessively acid for the crops that are grown.

Nitrogen, phosphorus, potassium, sulfur, magnesium, boron, and other trace elements are insufficient for maximum yields on many soils. Soil tests or plant analyses are used as aids in determining the fertility status of specific soil areas.

Soil erosion is a serious problem on some slopes but is less prevalent than one might expect. Most of the sloping soils are protected by close-growing vegetation. Rainfall is usually of low intensity, and the sloping soils are fairly resistant to erosion. Moreover, a high percentage of the cultivated crops is grown on nearly level alluvial soils. Flooding causes serious erosion damage on the recent alluvial soils unless proper precautions are taken.

Problems of tillage and soil structure are variable and have not been studied extensively. Most of the upland soils (but not some of the alluvial soils) have desirable structure.

Specific soil-management problems and programs are discussed for each of five zones in the region.

ZONE 1 consists of the lowlands around Puget Sound in Washington.

Dairying, poultry, and horticultural crops provide its three main sources of income. Forage crops for use as pasture, hay, and silage are important. Grain is shipped into the area for the poultry industry.

Many of the wide range of horticultural crops are sold locally all types of fresh vegetables, small fruits (such as strawberries, raspberries, blackberries, and loganberries), potatoes, bulbs, nursery stock, and vegetable seed.

Continued urban expansion has taken many acres of fine agricultural land out of production.

More efficient systems of soil management must be adopted in the future in order to meet the increasing demand for agricultural products here.

Most of the soils used for agricultural purposes have been formed from some type of glacial material. The soils except the younger alluvial soils are highly leached and are moderately to strongly acid.

The key soil-management problems in the Puget Sound lowlands are: Inadequate drainage, droughtiness, poor structure or tilth, excessive acidity, inadequate fertility. The magnitude of the problems varies on different soils, with different management systems, and on different crops.

Much of the land originally was poorly drained. Many acres still have restricted drainage. They are used for timber and pasture.