SOIL-WATER DEPLETION BY C(3) AND C(4) PASTURE GRASSES IN CENTRAL APPALACHIA

Changing vegetation type can change soil water utilization patterns an d alter an area's hydrologic balance. This study was conducted to dete rmine the impact of changing hill land pastures from C3 to C4 grasses on soil water levels. Soil water status was monitored at 920 m (3,000 ft) elevation and 615 m (2,000 ft) elevation sites in Central Appalach ia. Plots were planted with a C3 grass-orchardgrass (Dactylis glomerat a L. var. 'Pennlate'), a C4 grass-switch-grass (Panicum vigatum L. var . 'Cave-in-Rock'); and another C4 grass-bermudagrass (Cynodon dactylon L. var. 'Quicksand Common'). At the 920 m elevation site, orchardgras s frequently maintained a 2-4 cm (0.8-1.6 in) greater soil water deple tion level than switchgrass or bermudagrass. There was no consistent s ignificant difference at the 615 m site. Additionally, there was no tr end of soil water depletion differences between switchgrass and bermud agrass at either site in spite of large differences in canopy height a nd geometry. Overall soil water depletion was greater at the 615 m sit e than at the 920 m site which may have been influenced by differences in soil properties. Higher water yield as streamflow may result from higher elevation sites when C4 grasses are grown rather than C3 grasse s.