Monday, November 5, 2007
74-1
Effect of Waterlogging on Development, 15N-Nitrate Uptake Capacity, and Emergence from Dormancy of Two Warm Season Grasses.
Benjamin Wherley1, Daniel Bowman1, Wei Shi2, Michael Jennette1, and Thomas Rufty1. (1) N.C. State Univ, Dept. of Crop Science, Raleigh, NC 27695, (2) N.C. State Univ, Dept of Soil Science, Raleigh, NC 27695-7619
Effluent irrigation on turfgrass is increasing in the southeastern U.S. due to population growth and environmental concerns. Effluent is generated continually and pressure exists on turf managers to over-irrigate. Extended periods of rootzone waterlogging may result, especially where heavy clay soils are compacted during construction. This issue led to experiments examining effects of waterlogging on development, nitrate uptake capacity, and emergence from dormancy of two warm-season turfgrasses considered to have differing tolerances to low oxygen conditions. Dormant grass/soil cultures of hybrid bermudagrass (Cynodon (L.) Pers. X C. transvaalensis Burtt Davy) and common centipedegrass (Eremochloa ophuiroides (Munro) Hack.) were removed from field plots and placed into a controlled environment chamber simulating spring transition (26/19C). Cultures were grown in continually waterlogged or well-drained conditions (35% or 15% gravimetric H2O content) for periods of 14 to 72 days. Waterlogging reduced canopy cover by ~30% in both species; however, shoot dry matter production was unaffected in centipedegrass and declined only after ~7 weeks in bermudagrass. Although centipedegrass root dry matter production was unaffected by waterlogging, the bulk of newly formed roots remained near the soil surface. Waterlogging reduced bermudagrass root dry matter production by ~40%, and tended to promote shallow rooting. Nonetheless, bermudagrass roots were more evenly distributed through the soil profile relative to centipedegrass. Total nitrate acquisition by both species was generally unaffected by waterlogging. Survival of these grasses under waterlogged conditions appears to be a result of adaptations that increase oxygen availability to root tissues. In centipedegrass, the adaptation appears to be the morphological shift to a shallower root system, and, from preliminary observations, it appears that bermudagrass adaptation may involve formation of aerenchyma tissues.