About 190,000 acres, or about 29 percent of the total acreage in Yolo County, are used for range. Generally, the soils used for range are not suited to cultivation. Forage production can be increased, however, in selected areas by adding fertilizer, controlling brush, and seeding adapted grasses and legumes.

Most of the important range forage plants in the county are introduced. The original forage plants were perennials and annuals, but the introduced plants are mainly annuals. In places, however, remnant perennials still grow at the higher elevations.

Management of grazing is needed to encourage a desirable mixture of annual plants. Livestock graze selectively, and they seek out the palatable and nutritious plants. If grazing is not carefully regulated, the more desirable plants are weakened or eliminated. Less desirable plants then increase. If grazing pressure continues, the less desirable plants are thinned out or eliminated and undesirable, unpalatable plants take their place or the soil is left bare.

The soils used for grazing in Yolo County have been grouped into range sites. Each site differs from the others in its ability to produce significantly different kinds and amounts of vegetation and in the management needed to keep the site in good condition. Important changes in the kinds of grasses often take place gradually. They can be overlooked by an operator who is not familiar with his range plants and soils. If the range operator knows the different kinds of soil in his holdings and the plants each kind is capable of growing, he can then manage the range to favor the best forage plants on each kind of soil.

In the pages that follow, brief descriptions of the four range sites in Yolo County are given. Annual airdry production is estimated for each site. These estimates are based on a limited number of clippings and on knowledge of the soils in the sites. The estimated annual yields of forage are for unfertilized range. These yields vary according to the precipitation received, and extremes in weather can cause even greater fluctuation in production.

The names of soil series are, given in each range site, but this does not mean that all the soils in a series are, in the range site. The soils in each site can be determined by referring to the "Guide to Mapping Units" at the back of this survey.

This site consists of silty clay loams and clay loams in the Balcom, Dibble, and Millsholm series. These moderately deep soils have a subsoil of silty clay loam and clay. Slopes are dominantly 30 to 75 percent, but in places they are less than 30 percent. Elevation ranges from 500 to 2,000 feet, and annual precipitation is 17 to 24 inches. This site occupies about 56,000 acres.

Available water holding capacity generally is 4.0 to 6.0 inches. In some more, shallow areas, however, it is 2.0 to 4.0 inches. Fertility is moderate.

The plant cover on this site is typically open grass or oak and grass. The vegetation is mostly annual grasses and forbs. If the, vegetation is producing at maximum, about 70 percent is a mixture of soft chess, wild oats, stipa, California brome, blue wildrye, burclover, filaree, annual clover, Spanish clover, and other desirable plants. About 20 percent of the vegetation is less desirable kinds of plants, such ripgut brome, red brome, wild barley, squirreltail, and annual lupine. The rest consists of annual fescue, medusahead, dogtail grass, nitgrass, silver hairgrass, tarweed, popcornflower, fiddleneck, turkey mullein, thistle, and other undesirable plants. In poor condition this site contains a few desirable and less desirable plants, but undesirable plants are dominant.

The soils in this site that have slopes of less than 50 percent can be seeded to hardin-grass,annual grasses, and legumes. Forage, plants on these soils respond well if fertilizer that contains nitrogen, phosphorus, and sulfur is applied. Seeding, fertilizing, and clearing should not be, done on soils that have slopes of more than 50 percent, unless the need is critical.

The total estimated annual air-dry production on this site is 3,300 pounds per acre in years of favorable moisture, and 1,600 pounds per acre in years of unfavorable moisture. The total estimated annual production that would provide forage for livestock is 2,800 pounds per acre in years of favorable moisture and 1,400 pounds per acre in years of unfavorable moisture.

This site consists of cobbly clays and clays in the Climara and Sehorn series and silty clay loams in the Balcom series. These moderately deep to deep soils are underlain by soft consolidated sandstone, shale, or serpentine. Slopes are 2 to 75 percent. Small areas of the more gently sloping soils are arable but are used for range. Elevation ranges from 100 to 2,000 feet, and annual precipitation is 18 to 24 inches. This site occupies about 62,000 acres.

Permeability of these soils is slow. Available water holding capacity is 4.0 to 10.0 inches, and fertility is low to high. Erosion is a hazard if a good cover of plants is not maintained.

The plant cover on this site is typically open grass or oak and grass. A few dense thickets of oak occur in areas that face north. The vegetation is mostly annual grasses and forbs. If the vegetation is producing at maximum, about 70 percent is a mixture of soft chess, ryegrass, filaree, annual clover, burclover, wild oats, remnants of perennial grasses, and other desirable plants. About 20 percent of the vegetation is less desirable kinds of plants, such as ripgut brome, red brome, wild barley, squirreltail, and annual lupine. The rest consists of annual fescue, mesudahead, nitgrass, dogtail grass, tarweed, fiddleneck, popcornflower, vinegar weed, turkey mullein, thistles, mustard, and other undesirable plants. In poor condition this site contains a few desirable and less desirable plants, but undesirable plants are dominant.

The total estimated annual air-dry production on this site is 3,600 pounds per acre in years of favorable moisture and 2,000 pounds per acre in years of unfavorable moisture. The total estimated annual production that -would provide forage for livestock is 3,300 pounds per acre in years of favorable moisture and 1,800 pounds per acre in years of unfavorable moisture.

This site consists of gravelly loams in the Cornin and Positas series. These soils have a subsoil of clay. They are 10 to 20 inches deep to soft consolidated material. Slopes are 2 to 50 percent. Elevation ranges from 125 to 1,500 feet. The annual precipitation is 16 to 24 inches. This site occupies about 33,000 acres. It includes large acreage that are arable but are being used for range.

Permeability of these soils is very slow. Available water holding capacity is 2.0 to 3.0 inches, but the clay subsoil provides additional slowly available moisture. Fertility is low.

The plant cover on this site is typically open grass or grass and oak. A few areas of brush occur in areas that face north. The vegetation is mostly annual grasses and forbs. If the vegetation is producing at maximum, about 70 percent is a mixture of soft chess, wild oats filaree, Spanish clover, annual clover, a small amount of burclover, and remnants of perennial grasses and other desirable plants. About 20 percent of the vegetation is less desirable kinds of plants, such as ripgut brome, red brome, wild barley, wild carrot, and annual lupine. The rest consists of annual fescue, medusahead, dogtail grass, silver hairgrass, nitgrass, plantain, thistle, fiddleneck, tarweed, popcornflower, and other contains a few desirable and less desirable plants, but undesirable plants are dominant.

The soils in this site that have slopes of less than 30 percent can be seeded to annual grasses and legumes. Forage plants on these soils respond well if fertilizer that contains nitrogen, phosphorus, and sulfur is applied. If chamise has invaded, growth of forage can be expected to be better where the areas are cleared of chamise.

The total estimated annual air-dry production on this site is 2,000 pounds per acre in ~ears of favorable moisture and 1,000 pounds per acre in years of unfavorable moisture. The total estimated annual production that would provide forage for cattle is 1,400 pounds per acre and for sheep and deer 1,700 pounds per acre in years of favorable moisture. It is 500 pounds per acre for cattle and 700 pounds per acre for sheep and deer in years of unfavorable moisture.

This site consists of loams in the Dibble and Millsholm series. These soils are 10 to 25 inches deep to shale or sandstone. Slopes are 9 to 75 percent. In a few areas rocks crop out and cover 2 to 10 percent of the surface. Elevation ranges from 500 to 2,500 feet. The annual precipitation is 20 to 24 inches. This site occupies about 39,000 acres.

Available water holding capacity is 2.0 to 3.0 inches. Fertility is moderate to low.

The plant cover on this site is typically open grass or grass and oak. A few dense thickets of brush occur in areas that face north. The vegetation is mostly annual grasses and forbs. If the vegetation is producing at maximum, about 70 percent is a mixture of soft chess, wild oats, filaree, burclover, annual clover, Spanish clover, annual lupine, and remnants of perennial grasses and other desirable plants. About 20 percent of the vegetation is less desirable kinds of plants, such as ripgut brome, wild barley, wild carrot, yarrow, and lupine. The rest consists of annual fescue, nitgrass, silver hairgrass, dogtail grass, popcornflower, fiddleneck. tarweed, thistle, and other undesirable plants. In poor condition this site contains a few desirable and less desirable plants, but undesirable plants are dominant.

Brush clearing and the adding of fertilizer have only limited application on this site. A few areas that have slopes of less than 30 percent can be seeded.

The total estimated annual air-dry production on this site is 2,400 pounds per acre in years of favorable moisture and 1,200 pounds per acre in years of unfavorable moisture. The total estimated annual production that would provide forage for cattle is 1,800 pounds per acre and for sheep and deer 2,200 pounds per acre in years of favorable moisture. It is 700 pounds per acre for cattle and 1,000 pounds per acre for sheep and deer in years of unfavorable moisture.