CropSyst User Manual - sipeaa

C Tc · K · (ψ l,sc - ψ l,wilt ) - 1.5 · Tr pot · ψ l,wiltψ l = ψs ·C Tc · K · (ψ l,sc - ψ l,wilt ) · 1.5 - · Tr potIf ψ l from equation is less than ψ [l,wilt] ( wilting leaf water potential input parameter ),then ψ l is set equal to ψ [l,wilt] .C l is the layer root conductance determined from current total root conductance (C Tc ) in (kg ·s/m 4 ) and the fraction of total root length in each layer:wheref lC l = f l · C Tcis the fraction of the total root length present in the l'th soil layer.C Tc is the current total root conductance calculated as:C Tc = C t · FractCover canopywhere C T is maximum total root conductance. This value can be estimated if amaximum uptake rate is assumed for a fully developed green crop, unstressed, fullywatered, with unrestricted root penetration, and under an environment providinglarge atmospheric evaporative demand. Under this set of conditions, any evaporativedemand larger than the maximum uptake rate will only induce stomatal closure.1.5 · WU maxC T =ψ fc - ψ l,sc · KwhereWU max (m/day) is the maximum uptake rate crop input parameter.ψ fc(J/kg) represents the soil water potential at field capacity.ψ [l,sc](J/kg) is the leaf potential just before the beginning of stomatal closuredue to water deficit a crop input parameter.