Evaporation from four cropping systems, i.e. willow, spruce, grass ley and barley, was compared in this simulation study. The physically based soil model had previously been used to simulate a wide variety of soil-plant systems. Climatic data obtained over six years from two stations in southern Sweden were used as model input. The stand parameters were mostly taken from the literature. The mean seasonal “crop coefficient” for the period from April through October, defined as the relation between the potential transpiration calculated by the Penman-Monteith (1965) formula and the Penman (1948) estimate, Eto, was about the same for willow and spruce (0.9), but was lower for grass ley (0.7) and barley (0. 4). Seasonal evaporation was highest for spruce (516 mm), slightly lower for willow (497 mm), and much lower for grass ley (419 mm) and barley (347 mm). Total evaporation and transpiration decreased linearly with the precipitation deficit, P< Eto, indicating reduced transpiration for all six years at the east coast and two years at the west coast. The difference in total evaporation between the trees (willow, spruce) and grasses (grass ley, barley) was most pronounced during growing seasons with a precipitation excess, P> Eto, and decreased linearly with the precipitation deficit to near zero at a deficit of 350 mm. Runoff increased with the precipitation excess, but for willow and spruce it was generally equal to or less than the excess. For the grass ley and barley, runoff exceeded the precipitation excess, P-Eto, by about 150 mm on a yearly basis.

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