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, O r, ~j 'I g 4 uo- . CHAFTER III ARABLE LANDS Utah-Colorado State line. Approximately 3,000 acres of arable land near Monticello are irrigated from small mountain streams, about 70,000 acres farther east are dry-farmed, and the remaining 48,000 acres are not cul- tivated. Almost all of the Monticello Area lands are on the Great Sage Plain. The surface of the plain is undulating or rolling with a wind- created swale and ridge type of topography. The southern sections are dissected by steep-walled canyons of intermittent streams tributary to the San Juan River. Medium-textured, reddish-brown aeolian soils occur over the greater part of the area. The soils are underlain mostly by creviced Dakota sandstone. Lands near the base of the Abajo Mountains are und,erlain by cobble, and lands in the bottom of a broad syr!cline or trough extending eastward through the center of the area from a point about 4 miles east of Monticello are underlain by Mancos shale. Soils in the syncline are derived mainly from the gray shale but are mixed with reddish-brown, wind-laid material. . The aeolian soils of the area have good moisture-holding capacity, high inherent fertility, and are free from harmful quantities of salts or alkali. The general area has good air drainage and a favorable grow- ing season for such a high elevation (7,100 feet at Monticello). Soils in the bottom of the syncline have slow permeability, low fertility, and sufficient salt to cause severe problems under irrigation. Air drainage in this part of the area is poor and the growing seaso!} shorter than in other parts. Higher lands of the area that lie on the portions of the synclinal slopes that are deeply dissected by streams would have a low drainage requirement. Lands on the lightly dissected slopes would have a moderate to high drainage requirement with irrigation. Drainage de- ficiencies increase downslope on all lands, becoming unrectifiable in the bottom of the syncline and in some of the swales. Blanding Area . Blanding Area lands lie on a series of finger-like mesas between deep parallel canyons of intermittent tributaries of the San Juan River. These lands are an extension of the Monticello Area lands and are simi- lar to lands in the southern part of that area. The swale and ridge type of topography is less pronounced in the Blanding Area, however, and the aeolian soils are more yellowish brown with less structural develop- ment because of lower rainfall. The srils are moderately deep over crev- iced Dakota sandstone. They are permeable, fertile, and easy to till. They have high moisture absorption and retention capacity and would pre- sent no problems of salt or alkali content. Approximately 20,000 acres in the northern part of the area are dry-farmed but low rainfall pre- vents dryfarming in the southern part. Land elevations range from 5,200 to 7,200 feet. Under irrigation lands on the ridges or mesas would have light to moderate drainage requirements except lands in swales or other low areas where the drainage deficiency would be unrectifiable. 29