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III IIIIIIIIIIIII III 999 10-Baller Variant-Lavina-Rock outcrop complex, 5 • 15 percent slopes. The areas of this complex are on hill slopes and ridges associated with extrusive volcanic flows and dikes. The average annual precipitation is 15 l0 17 inches, the average annual air temperature is 47' F, and the average (cost-free season is 126 to 142 days. Elevation is 5,600 to 6,500 feet. Baller Variant soil makes up 45 percent of this complex, Lavina soil makes up 25 percent, and Rock outcrop makes up 20 percent. Baller Variant soil is on hill slopes and ridges, Lavina soil is on hill slopes, and Rock outcrop is on shoulders and in eroded areas. The soils and Rock outcrop are in areas so intricately intermingled that it was not practical to map them separately at the scale used in mapping. Included in mapping are small areas of Denver and Kutch soils on hill slopes and terraces. The included soils make up about 10 percent of the total acreage. The Baller Variant soil is shallow and well drained. It formed in noncalcareous, gravelly, loamy material derived from volcanic rock. Typically, the surface layer is neutral, dark yellowish brown stony sandy loam about 3 inches thick. The lower part of the surface layer is neutral, brown to dark brown very gravelly sandy loam 5 inches thick. Below that, there is a layer of soft, weathered bedrock 9 inches thick. Hard bedrock (latite) is at a depth of 17 inches. Permeability of the Baller Variant soil is moderately ~pid. The available water capacity is low. The effective rooting depth is 10 to 20 inches. Runoff is medium to rapid, and water erosion is a severe hazard. Soil blowing is a slight hazard. The depth to hard bedrock ranges from 10 to 20 inches. The shrink swell potential is low. Rock fragments make up 35 to 60 percent of the volume. The Lavina soil is shallow and well drained. It formed in calcareous, clayey alluvium and loess deposited over hard volcanic rock. Typically, the surface layer is neutral, brown to dark brown loam about 5 inches thick. The subsoil is neutral, dark yellowish brown clay about 7 inches thick. Hard bedrock (latite) is al a depth of 12 inches. Permeability of the Lavina soil is slow. The available water capacity is low. The effective rooting depth is 10 to 20 inches. Runoff is medium to rapid, and water erosion is a severe hazard. Soil blowing is a slight hazard. The depth to hard bedrock ranges from 10 to 20 inches. The shrink-swell potential is moderate to high. Rock fragments make up 0 to 15 percent of the volume. Rock outcrop consists of exposures of volcanic rock, talus, and large boulders. In areas of Rock outcrop, plants can take cool only in cracks and fissures. Runoff is rapid, but water erosion is only a slight hazard. The soils in this complex are used mainly for grazing !nd as pasture, as habitat for wildlife, and as recreation areas. A few areas are used as a source of aggregate. The native vegetation is mainly big blueslem, mounlainmahogany, Griffith whealgrass, and sideoats grams. The average annual production of air-dry vegetation ranges from 300 to 700 pounds per acre. Proper grazing use and a planned grazing system are needed to maintain the quality and quantity of desirable plants and to prevent erosion. Periodic deferment of grazing during the growing season helps maintain or improve the range condition. Proper grazing use is needed to prevent depletion because the soils are dilficult to revegetate. Seeding speeds the revegelalion of areas depleted by heavy grazing or other disturbances. Small pastures commonly are severely overgrazed and eroded. Livestock in small pastures should be kept in pens. The rest of the pasture can be used as exercise areas and for very limited grazing. Grasses, shrubs, trees, and garden plants are dilficult to establish and maintain because of shallowness to rock, slope, and large stones. A mulch of plant residue helps reduce soil blowing and runoff, improve filth, and conserve moisture. Applications of manure and commercial fertilizers that contain nitrogen and phosphorus are needed to maintain fertility. Selecting adapted vegetation is essential in establishing plantings. Planting on the contour helps to conserve moisture and reduce erosion. Pebbles and cobbles should be removed from the surface in disturbed areas for best results in landscaping, particularly for lawns. Supplemental irrigation is needed at planting time and during dry periods. The main limitations to use of the soils for homesile development are the shallowness to rock, the slope, and large stones. The deep cuts needed to provide a sulliciently level building site can expose bedrock. Effluent Irom an absorption field can surface downslope and create a health hazard. The elfecls of shrinking and swelling in areas of the Lavina soil can be minimized by proper engineering design and by backfilling with material that has a low shrink-swell potential. Cuts and fills should be seeded or•mulched. Erosion and sedimentation can be controlled by maintaining an adequate plant cover. This complex is in capability subclass V1s. The Baller Variant and Lavina soils are in the Shallow Foothill range site and in plant adaptability group F-7.