PrHo quantifies crop water requirements based on two sub-models: a) a reference evapotranspiration (ETo) sub-model, and b) a crop coefficients (Kc) sub-model. The ETo sub-model computes greenhouse ETo values using outside solar radiation estimates retrieved from a radiation model previously calibrated for local conditions. Outputs from this sub-model make possible to adjust the irrigation scheme to particular crop conditions, such as white washing. The Kc sub-model computes the temporal dynamics of Kc values along the growing period, from the sowing/planting to the effective full cover stages. as a function of thermal time retrieved from greenhouse air temperature measurements.