Gerardo (Gerry) Spinelli
Production Horticulture Advisor for San Diego County
In The Spotlight
When water is applied to a nursery or a greenhouse container to keep plants hydrated, salts dissolved in the irrigation water are applied with it. As plants use water, most salts are left behind and increase the salinity of the container substrate. Additionally, fertilizers consist of soluble salts and their use raises the total salinity of the soilless substrate to which they are applied. To avoid excessive salt buildup, irrigation is used as a management tool to leach excess salts from the substrate. This means that an additional quantity of water should be applied to the container to leach salts. This water is applied in addition to the volume that the substrate can hold and results in leachate. The ratio of the leachate to the total volume of water applied is called the leaching fraction. Improper management can results in wasting water and fertilizer, while leaching excess salts could result in environmental damage if the runoff is allowed to move off site. In these videos we describe methods to measure the leaching fraction applied in the field and to calculate the appropriate leaching fraction for your conditions.