BELLANI EVAPORATION VARIATION IN HILL-LAND PASTURE

In the Appalachian region, pasture production is frequently limited by water availability, a parameter strongly influenced by microclimate variability. This study was conducted to determine the magnitude of potential evaporation variability across a hilly pasture on a seasonal basis. A steep pasture watershed was instrumented at 32 sites with black and white Bellani plate evaporimeters. Evaporation was measured during the summers of 1985, 1986 and 1987. Average potential evaporation, assessed by readings from black plate evaporimeters, ranged from 4.5 to 6.1 mm day-1 averaged over the frost-free period, June-September. Over the same period and across the same area, solar radiation was estimated to vary from 11.9 to 16.9 MJ m-2, and wind from 50 to 131 km day-1. These substantial microclimate differences suggest the importance of developing management practices suited to specific sites within hilly pastures. © 1990.