In counties where one set of sample units provided adequate data, the set 

 outlined in red was used. No substitution or intermingling of the two 

 sets was permitted. 



All possible use was made of existing soil-survey information. For coun- 

 ties with recently completed surveys no additional field work was needed. 

 In other counties, onsite surveys produced new maps that provided the 

 information. 



On sample units not already mapped, soil surveys were made on the regular 

 aerial photograph field sheets at the scale locally used. In partially 

 mapped counties, surveys of sample units were made according to the legend 

 in use in the county. Insofar as possible, all new mapping was done ac- 

 cording to legends that could be used in the standard soil survey. 



In mapping the samples, urban and built-up areas were classified as to 

 land use only. 



Federal land identified on the sample unit map was generally not mapped. 

 If the Federal land included cropland farmed under lease or permit rather 

 than by the agency, and if a total acreage of such land in the county could 

 be obtained from the agency, that falling in sample units was mapped. On 

 Indian lands, the Bureau of Indian Affairs assisted in getting survey 

 information. 



All existing maps of sample units were field checked before use. The map 

 was revised if the soil survey was not adequate or if the land use shown 

 did not agree with present conditions on the ground or with the inventory 

 definitions. Revisions were made on copies of the maps instead of on the 

 original soil-survey field sheets. 



One of the major values of the survey data will be to show the relation 

 of land use to the physical conditions of the land. Land use was mapped 

 on all sample areas. The condition found at the time of the mapping was 

 shown, with no attempt to predict the intent of the operator. 



Land use was designated as s Irrigated cropland, nonirrigated cropland, 

 pasture range, irrigated native grassland, forest and woodland, and other 

 land. Definitions used in soil-survey mapping were those used for the 

 Inventory of Soil and Water Conservation Needs, 



In measuring sample unit maps, each individual mapping unit was measured 

 separately so the data could be combined by land-capability units or 

 other desired interpretative groupings. 



The soil and land use data from the sample units were then expanded to 

 give figures representing the total acreages of conditions in the county. 

 This expansion was done by Iowa State University. 



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