where h is the average maximum crop height (m), fc eff is the effective fraction of ground covered or shaded by vegetation near solar noon. When the rows of plants run from north to south, fc eff ≈fc
since the soil is exposed to the sun at various times of the day,and the shaded area is the same as the fraction of vegetation cover at midday (Allen et al., 1998).
The ML parameter (a multiplier of 1.5–2.0) describes the effect of canopy density on shading and on maximum relative ETc per fraction of ground shaded.
The parameter Kc full in Eq. (2) can be approximated as a function of crop height and adjusted for climate (Allen et al., 1998; Allen and Pereira, 2009):