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Garden with Insight v1.0 Help: Soil patch next day functions: calculate today's soil cover index

The soil cover index is a little strangely named, because it is an index of the extent to which the soil is *not* covered up by vegetation or snow. It is used to calculate albedo (radiation reflection) and evaporation. A soil cover index of 0.0 means the soil is completely covered, and a soil cover index of 1.0 means the soil is bare.

If there is at least five millimeters of snow on the soil patch, the soil cover index is set at 1.0. This sounds strange because the soil is not bare, but albedo calculation deals with snow separately (so the 1.0 doesn't matter for albedo), and snow cover poses no barrier to evaporation. Evaporation takes water from the snow on the soil patch before it takes water from the soil.

If there is no snow, the soil cover index is exp(-0.05 * x) where x is the total of all above-ground live biomass (in plants), above-ground standing dead residue (in plants), flat residue in the mulch, and flat residue in the first soil layer. (Note that the abbreviation "exp" here means "e to the power of".) The graph of soil cover index versus vegetation cover looks like this:


If the "update soil cover" option is turned off, this calculation is not done and yesterday's soil cover index value is carried over to today.

calculation of albedo, soil evaporation
EPIC Evapotranspiration
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Updated: May 4, 1998. Questions/comments on site to
Copyright © 1998 Paul D. Fernhout & Cynthia F. Kurtz.