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soil survey of Weld County, Colorado Northern Part By James A. Crabb, Soil Conservation Service ., '. Fieldwork by James A. Crabb, Peter L. Smith, and Dwight E. Curtiss, Soil Conservation Service United States Department of Agriculture, Soil Conservation Service and Forest Service, in cooperation with Colorado Agricultural Experiment Station WELD COUNTY, NORTHERN PART, is in the northeastern part of Colorado. It is north of Denver and east of the Rocky Mountains. The total area is 1,4:;19,520 acres, or about 2,233 square miles. Greeley, the county seat, is in the soUthern part of the county. Most of the acreage in the survey area is used as rangeland and nonirrigated cropland. A small acreage is used as irrigated cropland. Descriptions, names, and delineations of soils in this soil survey do not fully agree with those on soil maps for adjacent counties. Differences are the result of better knowledge of soils, modifications in series concepts, intensity of mapping, or the extent of soils within the survey. general nature of the survey area This section discusses the physiography, drainage, and relief and the climate in the survey area. It also discusses the Pawnee Nationai Grassland. physiography. drainage, and relief The survey area is in the northern part of the Colorado Piedmont. It is in three distinct physiographic areas. A knowledge of the location and nature of these areas helps in understanding the soils and agriculture in the survey area. The largest part of the survey area is on a gently undulating to rolling plain. This part has great agricultural value. The soils on the plain formed mainly in alluvium. Also on the plain are some areas of reworked old alluvium, wind-modified alluvium, and exposed weathered bedrock, which borders the escarpments to the north. The most easily observable physiographic area is the escarpments that extend across the survey area from west to east. "Chalk Bluffs" and "Pawnee Buttes" are in this area. The escarpments are rolling to steep, and they consist of rock outcroppings of siltstone that commonly have a cap of sandstone. Deposits of material derived from siltstone, sandstone, and some shale are directly below the escarpments. The escarpments are used mainly for cattle grazing and wildlife habitat. To the north and at a higher elevation than the escarpments is a gently undulating to rolling high plain. The soils on this plain formed in alluvium and residuum derived from sandstone. The high plain has agricultural value. The survey area is drained by numerous intermittent .creeks. Some of the major creeks in the western part of the survey area are Spring, Lone Tree, Owl, and Crow Creeks. They flow in a southerly direction through the survey area and jcin the South Platte River outside the area. The major drainageways in the eastern part of the area are Sidney Draw and Cedar and Pawnee Creeks. Sidney Draw flows in a northeasterly direction through the survey area and joins Lodgepole Creek in Nebraska. Cedar and Pawnee Creeks drain to the east and join the Scuth Platte River in Logan County. ' Elevation in the survey area ranges from approximately 6,350 feet at the extreme northwestern corner to 4,300 feet where Pawnee Creek flows from the area to the east. 1