Surface energy balance partitioning over rye and oats cover crops in central Iowa

ABSTRACT:

Evaporation from fields, sub-basins, and watersheds during the fall and winter period has been assumed insignificant relative to the yearly water balance. The partitioning of surface energy balance components over an oat/rye cover crop during the fall and winter periods has not been routinely conducted and is not entirely understood. The objective of this study was to evaluate surface energy partitioning over an oat/rye cover crop and bare soil beyond the normal growing season. In central Iowa three fields representing an oat and rye cover crop and a bare soil were instrumented to measure net radiation, soil, sensible and latent heat fluxes using a Bowen-ratio technique. Monitoring from October through March was conducted for three years beginning in 1994 and ending in 1997. Results show that energy partitioning at the surface over rye, oats, and bare soil during the fall/winter period is driven by climate, snow, residue cover, and available energy. Seasonal evaporation totals from mid-October through late-February ranged from 118 to 205 mm for the 3 year study.