Compared to most food crops, floricultural and ornamental greenhouse crops use large amounts of irrigation water per square foot of production area. This is because of shallow soils in containers and raised beds and because of high leaching requirements when nutrient solutions are added. As a result of the large amounts of water generally being leached and its high nutrient content when fertilizers are injected into the irrigation stream, there is increasing pressure to (1) conserve water in greenhouse operations and (2) avoid contamination of surface- and ground-water supplies by reusing nutrient solutions and runoff water that might otherwise move off the premises.