Some 500 million years ago a geological uplift, known as the Cincinnati Arch, occurred in what is known today as the Bluegrass Region.  As this anticline weathered over time, a layer of Ordovician limestone became the parent material for the productive soil located throughout the Inner Bluegrass Region (Atlas of Kentucky).  This limestone is rich in both phosphorous and calcium, and believed to be responsible for the production of strong bones in horses and other animals grazing upon its grasslands.  This phenomenon occurs in only one other location in the U.S., the Nashville Basin of Tennessee, recognized by the National Farmland Trust as one of the nation's 20 most threatened landscapes (Olson & Lyson, p.27).

The Bluegrass Region landscape is characterized by the broad rolling hills and sink holes typical of Karst topography. The regional topography consists primarily of the Maury Silt Loam soil association considered prime agricultural soils for row crops, equine production, and pasture land.  A unique aspect of this region is that the best soils are located on the top of these gently rolling, broad ridgetops, and thus are the deep, well-drained soils sought after both for agricultural use and urban development.  Soil type was identified in this study as one of the most critical resource elements in the region.  The Natural Resource Conservation Service classifies soils in the area as primary, secondary, and tertiary (USDA, Soil Conservation Service Maps).  For the purpose of this study, soils were classified by their suitability for equine production, suitability for crop cultivation, and degree of slope.  This resulted in the identification of six categories that describe the soils of the region.

The first category consists of the Maury Silt Loam soils most suitable for row crops and equine production due to the soil quality and occurrence on gentle slopes.  The second category includes soils with a slightly smaller percent of Maury Silt Loam and a slight increase in slope, making these soils of secondary importance for row crop and equine use.  The third category contains the least amount of Maury Silt Loam and a majority of the Maury-McAfee soil association along with slopes sufficiently gentle for some row crop and equine use.  The fourth category does not include the Maury-McAfee soil association  but is considered suitable for row crops in some situations, though it is not sought out for equine use.  The fifth category of soils is of moderate quality with areas characterized by severe slopes, making them less desirable for row crops and equine use.  The sixth group includes those soils located along the Kentucky River Palisades and the Knobbs where steep slopes and eroded soils limit crop production and equine potential.

Using these soil categories, generalizations can be made about the suitability of the region’s land for the three basic types of development:  equine and agricultural production, residential development, and commercial development.  For example, in Clark and Bourbon counties, the degree of slope is identified as the limiting factor when evaluating soil suitability, while in Madison County the mineral content makes the soil suitable for most agricultural purposes but not for equine use.

In 1967, horse farms occupied the majority of category 1, 2, and 3 soils and were located primarily in the core of the Bluegrass Region (Environmental Resources of the Lexington, KY Metropolitan Area).  By comparing the location of horse farms in 1967 with those of 1997, one can see how the concentration of the equine industry has begun to move outward, toward the edges of those soils deemed most suitable for equine production  (Kentucky Thoroughbred Association).  As thoroughbred farms have been displaced by urban growth, they have moved approximately four miles beyond the 1967 core area.  Based on the finite availability of these unique resources, the question becomes can they continue to relocate?

Using the soils, slope, cultural features and other inventory data, an Equine Resource Area (ERA) was identified. In order to insure the thoroughbred industry’s viability, a critical mass of stallions and mares must be maintained for diversity within this zone.  Approximately 92,000-93,000 acres of land in this region is devoted to thoroughbred farms.  This distribution occurs on 468 farms, averaging 177 acres per farm devoted to thoroughbred production.  A digital  map was produced depicting thoroughbred farm density within the region.  Each square on the map represent horse farms at their approximate size and location in the region.  In the upper left hand corner of the map is a graphic representation of the total land devoted to thoroughbred production in the region, illustrating how that acreage compares in size to the region as a whole.  The industry requires this acreage to maintain its present status of 420 stallions along with enough brood mares to produce approximately 8,600 foal per year.  (Kentucky Thoroughbred Association).  Any increase or decrease in total acreage or number of horses can be used as an indicator to measure the viability of the equine industry.

A chart was created to illustrate the number of thoroughbred horse farms per county in 1997. Based on information obtained from the Kentucky Thoroughbred Association, there has been an increase of 145 horse farms in the region since 1967, with a similar increase in the number of thoroughbred horses in the area during the same period.  This indicates the region’s equine industry is continuing to thrive and expand.  As this industry expands, additional demands will be placed on the total land resources and the rate of conversion of agricultural land to equine production will increase.