Modified solar insolation as an agronomic factor in terraced environments

We present a model that calculates incident solar radiation falling on terraced and unterraced fields in steep slope environments. The results are presented as a function of altitude, latitude, slope aspect, slope angle, and season. The net solar benefit or cost from slope leveling (terracing) differs significantly according to these situational factors. For instance, terracing will confer a net direct solar radiation benefit of 15 per cent on south-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° N latitude. Modified solar radiation must be considered as potentially important in the historical origins, functioning and abandonment of terracing. It should be a component in agronomic evaluation of modern terrace construction, restoration, or maintenance. Copyright (C) 2000 John Wiley and Sons, Ltd.