The 2009 ASHS Annual Conference

Sub-irrigation for production of potted ornamental plants combats the waste of water and fertilizer in traditional overhead watering systems used in greenhouses.  However, current ebb and flow watering systems for flooded floors operate slowly. The root medium takes up water to near saturation during each watering cycle. There is no ability to restrict the water provided to the plants. We have examined a system to rapidly deliver and remove water. Less water is absorbed by the pots, and little leaked back out of the pots. This improves plant quality and prevents spread of disease. We examined several parameters that vary between this partial saturation ebb and flow watering (PSEFW) compared to a control with more complete saturation when used on benches or floors. The amount of water taken up in a single watering could be varied from 30 to more than 70% of root medium volumetric water content (VWC), depending on the time of contact with water. When used repeatedly to grow a crop, plants took up 20 to 30% less water and fertilizer with PSEFW compared to control watering. The average VWC was 10% less with PSEFW compared to controls. The water stress resulting from PSEFW reduced biomass until flower development and bloom, and stem height, by 10 to 20% compared to control watering.