A spray application device, comprising: - at least one diluent reservoir for holding a diluent; - at least one formulation reservoir for holding a formulation comprising an active ingredient; - at least one formulation flow rate control unit; - a processing unit; - at least one mixer unit; - at least one spray unit; wherein, the at least one formulation flow rate control unit is configured to regulate the volume flow of the formulation into the at least one mixer unit, and wherein, the at least one mixer unit is configured to mix the diluent from the at least one diluent reservoir with the formulation comprising an active ingredient from the at least one formulation reservoir to obtain a mixture, and wherein the at least one spray unit is configured to spray the mixture, wherein, the at least one spray unit is configured to implement pulse width modulation to spray the mixture, and characterized in that the spray application device is configured to spray a constant concentration of the active ingredient per hectare as a function of variable mixture spray volume comprising a determination by the processing unit of at least one instruction to control the at least one formulation rate control unit and the at least one spray unit to maintain the dose of the active ingredient constant per hectare while changing the application mixture volume per hectare. - at least one diluent reservoir for holding a diluent; - at least one formulation reservoir for holding a formulation comprising an active ingredient; - at least one formulation flow rate control unit; - a processing unit; - at least one mixer unit; - at least one spray unit; wherein, the at least one formulation flow rate control unit is configured to regulate the volume flow of the formulation into the at least one mixer unit, and wherein, the at least one mixer unit is configured to mix the diluent from the at least one diluent reservoir with the formulation comprising an active ingredient from the at least one formulation reservoir to obtain a mixture, and wherein the at least one spray unit is configured to spray the mixture, wherein, the at least one spray unit is configured to implement pulse width modulation to spray the mixture, and characterized in that the spray application device is configured to spray a constant concentration of the active ingredient per hectare as a function of variable mixture spray volume comprising a determination by the processing unit of at least one instruction to control the at least one formulation rate control unit and the at least one spray unit to maintain the dose of the active ingredient constant per hectare while changing the application mixture volume per hectare. wherein, the at least one formulation flow rate control unit is configured to regulate the volume flow of the formulation into the at least one mixer unit, and wherein, the at least one mixer unit is configured to mix the diluent from the at least one diluent reservoir with the formulation comprising an active ingredient from the at least one formulation reservoir to obtain a mixture, and wherein the at least one spray unit is configured to spray the mixture, wherein, the at least one spray unit is configured to implement pulse width modulation to spray the mixture, and characterized in that the spray application device is configured to spray a constant concentration of the active ingredient per hectare as a function of variable mixture spray volume comprising a determination by the processing unit of at least one instruction to control the at least one formulation rate control unit and the at least one spray unit to maintain the dose of the active ingredient constant per hectare while changing the application mixture volume per hectare.