Comment:

If the normal wind erosion calculation is to be utilized (Wind Erosion Adjustment Factor (ACW) = 1.), field dimensions and orientation must be specified. This variable refers to the length of the field that is exposed to the wind. Without trees, FL = length of the field. With trees, FL < length of the field. If wind erosion is simulated for specific sites, FL, FW and ANG can be measured easily. However, hypothetical sites are often used in long-term simulations associated with large-scale decision making. In such cases, values of FL, FW and ANG should be chosen to represent typical field configurations of the area. Efforts to match field dimensions and drainage area are not necessary. The field dimensions are used only to estimate wind erosion, with the exception that FL is used to estimate water erosion from furrow irrigation. Thus, the simulation site may be a small area (1 ha) in a field of 1.0 by 0.5 km. It should be noted that the change in simulated wind erosion is not large for any FL > 0. 3 km. Therefore, estimations of FL and FW are not usually critical for fields with areas greater than about 10 ha. When fields larger than 10 ha are strip cropped, however, the estimation of FW becomes more important. To evaluate the effect of strip cropping, FW is estimated as the average width of the strips. FL may be left at 0.0 if unknown, and it will be estimated. (Range: 0.001-12). The value of this variable is determined by the class variable Subarea.