Learn and Grow
Have you ever had difficulty to properly re-wet your growing media after it became dry? Hydrophobic organic materials play tricks on you! Our researcher R & D Manager, Ph.D. Reza Nemati, explains how wetting agents are the solution for this frequent problem.
Hydrophobic Organic Materials
Growing media are composed from several components. Under dry condition, some of these components, like sphagnum peat moss and bark, can develop hydrophobic properties; water, already missing in the soil, becomes more hardly absorbable.
This hydrophobicity is caused by a range of hydrophobic organic materials, like waxes, resins, and organic acids. When they are dry, they form a non-polar “coating” on the substrate particles. Non-polar substances are not easily wettable in water, which is a polar substance. So, the coating repels water and the substrate fails to wet and to rewet under dry condition.
Wetting Agents Effects
That’s why during formulation of growing media, we should include a wetting agent to make sure that substrate is going to have a good wettability.
Wetting agent reduces hydrophobic behavior of growing media by decreasing surface tension of water. By having a hydrophilic property, it attracts water while clinging to the hydrophobic non-polar surface.
Wetting Agents Categories
There are three types of additives that help to overcome the hydrophobic characteristics of growing media: mineral, synthetic and natural additives.
Clay, brick dust, perlite, sand, perlite and zeolites are all examples for mineral additives.
The synthetic organic additives are the most frequently used in growing media industry. When we use them around recommended application rate, they are generally efficient.
However at too high rate they may present some adverse impacts on plant growth. Synthetic wetting agents are non-ionic, amphoteric, cationic or anionic.
The last category is the natural organic additives for example coconut husk fiber, and some plants extracts, like Yucca extract or Saponins.
Wetting agents can be applied by several forms: it can be incorporated directly to growing media. Or it can be applied through irrigation or fertigation systems. It can be also applied as a drench or as a mist to cuttings.
In brief, wetting agent improves water penetration and insures a uniform wetting and offer long term re-wetting. Wetting agent can improve some of substrate physical properties like water-holding capacity and drainage. It helps to optimize water utilization and nutrient management. By doing all these beneficial impacts, wetting agent improves plant growth & development.