The van den Berg-Driessen model (van den Berg and Driessen, 2002) estimates root fractions and root length densities in each soil layer as a function of root biomass in the soil profile and root depth. The empirical approach reported here has a general, but only indicative value. The application of this approach must be considered as last resort for estimating root distribution. Specific knowledge of root distribution linked to crop, soil characteristics, and simulation of root growth are more suitable in almost all cases.

The root fraction in each layer is calculated as:

where RootFractioni is the fraction of total roots at the layer i (0-1), BottomDepthi is the depth of the bottom of layer i (cm), TopDepthi is depth of the top of layer I (cm), RootDepth is the depth reached by roots (cm) and all coefficients are derived empirically.

The biomass fraction is computed as:

where RootFractioni is the fraction of total roots at the layer i (0-1), RootBiomass is the total root biomass (kg ha-1) and BiomassFractioni is the root biomass at soil layer i (kg ha-1).

The calculation of root density is done according to the following equation:

where BiomassFractioni is the root biomass at soil layer i (kg ha-1), Thicknessiis the layer i thickness, RootLengthDensityi is the root length density at layer i (m m-3)and 10.5 is the conversion factor from root biomass to root length (m kg-1).

Created with the Personal Edition of HelpNDoc: Full-featured EBook editor