Drilling fluids or muds are used while drilling oil and natural gas wells to lubricate and cool the drill bit, and to control subsurface wellbore pressure. They also function to remove drilled-out rock cuttings from the well, clean the bit and the bottom of the hole, and stabilize the wellbore. In western Canada, non-toxic, water-based, waste drilling fluids are often applied to cropland and sometimes native prairie at controlled, low application rates as a disposal option. There is concern, however, that application of drilling waste on native prairie in semi-arid climates may alter the soil surface energy balance, which in turn may adversely affect soil biophysical processes in these fragile ecosystems. This study was initiated to examine the effects of water-based drilling mud application on soil properties and native vegetation composition in a semi-arid mixed-grass prairie. In this poster, we address the relationships between differential rates (0, 40, and 80 m³ ha^-1) of summer-applied drilling mud and soil surface albedo and soil heat flux assessed for up to 60 d starting from the day of treatment application. Results are presented based on measurements of incoming solar and reflected radiation, and on soil temperature, soil moisture content, and soil heat flux in the 0-7.5-cm depth.