Deep Flow Hydroponics - Past, Present and Future

In 1976, a method of growing lettuce and other leafy vegetables on a floating raft of expanded plastic was developed independently by researchers at the University of Arizona and the University of Pisa in Italy. Today facilities exist in a number of countries including the United States, Japan and Canada. Termed “Deep Flow Hydroponics,” the system consists of horizontal, rectangular shaped tanks lined with plastic and filled with nutrient solutions. Those developed in Arizona measured 4 m x 70 m, and 30 cm deep. This method of hydroponics continues to grow in popularity due to the ability to control root temperatures, either by heating the nutrient solutions or chilling the solutions to reduce bolting, especially important in tropical and desert regions of the world. Concurrent with the development of the production system, were harvesting and packaging experiments. Packaging individual heads in air-sealed plastic bags extended the shelf-life up to three weeks, plus provided protection during transportation. Today, with the introduction of new specialty, leafy vegetables as those common in Mesclun (a variety of tender leafy salad greens) a renewed interest has been created in deep flow hydroponics.