Data from the Nebraska Agricultural Statistics Annuals, the Nebraska dnr website, and the Nebraska Databook website were used to compile the percentage of land within each county in the COHYST area devoted to six major crop categories - corn, wheat, soybeans, sorghum, hay, and 'others' (oats, sugar beets, dry beans). The information presented is for the years 1946, 1973, and 1997, representing land use practices at the beginning, middle, and end of the timeframe for the COHYST model. Included are tabulated data showing the total number of acres planted in each county and the percentage of land area used for each particular crop. In addition, maps of the COHYST area for each major crop category and year showing ranges of the percent of land used in each county are included.

For the counties with borders completely within the COHYST area, the percent of land area used for each crop was calculated simply by taking the total number of acres harvested for each crop divided by the total land area in acres for the county. For the counties that are on the border and not entirely within the COHYST area, the percent of the county land area within the COHYST area was calculated by finding the area of the county that is in the COHYST area using ArcView and then dividing this value by the total area for the county. The total number of harvested crop acres for the county was then multiplied by this percentage, assuming that crop production is distributed over the entire county area. This assumption is likely more valid for counties with a higher percentage of land within COHYST, e.g. - Garden, Arthur, and Hayes counties and less valid for counties such as Furnas, Sheridan, and Platte.

Ranges of percentages used in the map scales were kept consistent as much as possible, but for some crops the jumps in percentages were so large that new ranges were necessary. For example, soybeans and sorghum have different ranges for the 1946 and 1973 maps in order to show detail in variability for each county.

The values presented on the maps for each crop type is a sum of irrigated and non-irrigated totals. From previous graphs prepared on this data, non-irrigated crops dominated in 1946, whereas irrigated crops were more prevalent in 1973 and 1997, especially for corn. However, non-irrigated values were still much higher than irrigated for wheat and sorghum.

Of the six crop types, corn production, as expected, dominated the percent of county land used in the COHYST area. In 1997, several counties in the eastern COHYST area had 50-75 percent of the total county land area devoted to corn. Crops classified as 'others' showed a sharp decrease from 1946 to 1973 in the eastern counties. Hay production remained the most consistent of the crops in the 51 year time period. Land devoted to wheat production decreased significantly in the eastern counties from 1946 to 1997. For example, five counties in 1946 showed values from 15 to 50 percent of land devoted to wheat, whereas in 1997 only a maximum of two percent of the land in these counties was used. Land used for wheat in the panhandle remained very consistent throughout the time period. Sorghum production skyrocketed between 1946 and 1973 in the southeastern portion of the study area, where values increased from around one percent to nearly 25 percent. However, in 1997, land use for sorghum declined to the 3-10 percent range. The same trend is seen with soybeans, when in 1946, less than one percent of land in any county was devoted to soybeans. At the end of the timeframe for the study, up to 30 percent of some counties were planted with soybeans.