<p>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 proportion of said carrier liquid flow from pressure drop measurements of the proportional liquid flow, displacing active liquid with said proportional liquid flow without liquid contact, and including said displaced active liquid in said carrier liquid flow, thereby producing a liquid mixture in said 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.</p>
