Abstract: A method of preparing a mixture of a carrier liquid and an active liquid in required proportion including: providing a flow of carrier liquid, controlling a liquid flow to an appropriate portion of the carrier liquid flow from pressure drop measurements of the proportional liquid flow, displacing active liquid with the proportional liquid flow without liquid contact, and including the displaced active liquid in the carrier liquid flow, thereby producing a liquid mixture in the required proportion without a flow meter. The mixed liquid may be used in at least one of a sprayer and a nutrient film equipment. The displacement medium may be provided from the carrier liquid supply.