Cover St ory
By Tom Samples, Ph.D., and John Sorochan, Ph.D., The University of Tennessee
T
urfs are composed of leaves, tillers, thatch and fibrous roots, and depending on the turfgrass species, they may also have a contiguous network of above- (stolons) and/or belowground (rhizomes) stems capable of producing new plants. Because aerial shoots and thatch are located above the surface of the soil and are more noticeable, these two zones often receive more attention than the roots and the soil. The physical, chemical and biological properties of soil in which turfgrasses grow, however, have a major impact on turf performance and longevity.
Ecoregions The adaptability of a particular turfgrass species or variety in a specific region, or ecoregion, is determined by the environmental conditions it will encounter. The 18
World Wildlife Fund Classification includes a total of 867 ecoregions worldwide, of which the Global 200 are identified as the most biologically distinct terrestrial, freshwater and marine ecoregions on earth. An ecoregion of land is a relatively large area containing geographically distinct natural plant and animal communities with boundaries that approximate those of the original natural environment before a major change in land use occurs. The TN Department of Environment and Conservation recognizes eight ecoregions statewide (Figure 1). In terms of percent of total land area from greatest to least, they are: Interior Plateau (37.4%), Ridge & Valley (18.2%), SE Appalachians (12.1%), SW Appalachians (11.4%), Mississippi Valley Loess Plain (10.7%), Blue Ridge Mountains (6.0%), Central Appalachians (2.1%) and Mississippi Alluvial Plain (2.0).
TENNESSEE TURFGRASS decemBER/january 2016 Email TTA at: tnturfgrassassn@aol.com
Soil classification Similarly, soils are also grouped according to specific characteristics. The U.S. Dept. of Agriculture soil-classification system recognizes six levels ranked from most general to most specific as order, suborder, great group, subgroup, family and series.
Dominant soil orders There are 12 dominant soil orders in the U.S. Two common dominant soil orders in TN are Alfisols (Photo 1), which make up about 10% of the world’s ice-free land surface, and Ultisols (Photo 2), which make up about 8% of the worlds ice-free land surface. Alfisols, the most common dominant soil order in much of West TN, are soils in semi-arid to moist areas formed from weathering processes that leach clays and