Wetting agents are from a class of chemical compounds known as surface active agents or ‘surfactants.' As a component of growing media, wetting agent lowers the surface tension of water allowing it to spread and penetrate. Wetting agents do this by weakening water’s cohesive properties and strengthening its adhesive properties. Wetting agents are an important and invaluable component of growing media. However, the initial application of wetting agent to growing media can lose its effectiveness over time. This is influenced by microbes found in the organic components of growing media, aging and storage conditions prior to use. Once the growing medium is in use, wetting agents generally perform satisfactorily for about eight to 10 weeks, on average. But its effectiveness can diminish with time based on its chemical composition, the influence of the greenhouse environment, microbe interaction at the root zone, type of crop grown and irrigation schedule. With this, water penetration and rewetting characteristics of the growing medium can become less effective with each wet and dry cycle the growing medium undergoes, particularly with long-term crops such as poinsettias.
Benefits of reapplication
To correct this, reapplication of wetting agent may be required by the grower. Reapplication of wetting agent to ‘in-use’ growing medium reduces ponding and channeling of water through containers to minimize wet and dry areas within the growing medium. Growing media that rewets quickly saves labor, water and fertilizer and improves the distribution of dissolved fertilizers, pesticides and other chemicals. Further, wetting agents improve root growth and improve air to water ratios in growing media. In the end, reapplication of wetting agent allows the plant to utilize 100 percent of the growing medium for water and nutrients to reduce plant stress and improve plant health.
What to use
Use only non-ionic, premium quality wetting agents that are designed for growing media. Although most products are available as liquid concentrates or granular forms, generally the liquid forms are easier to use and apply as: drenches every four to six weeks; lower rates on a weekly basis; or integrated into a constant application regime with fertilizer solutions. Overall, wetting agents used at low rates on a continuous basis provide the best insurance against wetting issues. Follow manufacturers’ directions for proper application rates.
Wetting agents improve post-production success
Research has demonstrated that reapplication of wetting agents during crop production helps alleviate wetting problems after crops leave the protective confines of the greenhouse/nursery production facilities. In addition, drenching with a wetting agent prior to shipping can greatly reduce plant stress associated with retail displays, which ultimately benefits the consumer.
Use wetting agent to maximize the successful production of your crops and to minimize re-wetting situations that could be problematic for finished crops at retailers and consumers.