Modified solar insolation as an agronomic factor in terraced environments

We present a model that calculates incident solar radiation falling on terr aced and unterraced fields in steep slope environments. The results are pre sented as a function of altitude, latitude, slope aspect, slope angle, and season. The net solar benefit or cost from slope leveling (terracing) diffe rs significantly according to these situational factors. For instance, terr acing will confer a net direct solar radiation benefit of 15 per cent on so uth-facing 30-degree slopes at the Equator for a typical growing season; it will reduce net annual direct solar receipt by 21 per cent on south-facing 30-degree slopes at 45 degrees N latitude. Modified solar radiation must b e considered as potentially important in the historical origins, functionin g and abandonment of terracing. It should be a component in agronomic evalu ation of modern terrace construction, restoration, or maintenance. Copyrigh t (C) 2000 John Wiley & Sons, Ltd.