Are wetting agents worth the money?
Depends, say Washington State University soil and irrigation specialists in the fact sheet “Does Wetter Water Make Fatter Wallets?”.
Wetting agents are chemicals used to overcome the repellence of water in hydrophobic soils, potting mixes or soils high in organic matter, or thatch in lawns. They are sometimes recommended when gardeners complain that water is not penetrating the soil, either staying on the surface or running off.
Before using a wetting agent as a miracle cure for the problem, a gardener should investigate the reason for poor absorption. A wetting agent may help if the problem arises from hydrophobic conditions, but often there are other reasons that water is not easily penetrating the soil surface. In these situations — such as when the soil is compacted — wetting agents will not help.
Compacted Soil: Compacted soils are ones where the sand, silt and clay particles that make up soil have been physically compressed together, reducing the pore space between the particles. This reduces the amount of air in the soil and decreases the space available for water to move.
Home garden soil compaction can be caused by heavy equipment used in building, foot and vehicle traffic, regular shallow tillage with mechanical rototillers, or even by impact sprinklers.
The solution is to loosen the soil by working 3 to 4 inches of organic matter, such as quality compost, into the top foot of soil with a garden spade. For large areas you may need to use a tiller or a small tractor. In established lawn areas, aerating your lawn with a core aerator can help alleviate compaction in the top inch or more of soil, depending on how deep the cores. Wetting agents do not help relieve soil compaction.
Irrigation: When water is applied too fast, it will either sit on the surface until it filters down into the soil or it will run off because of a slope. This often occurs when soils are comprised of smaller clay and silt particles, because it takes longer for water to move into these soils. A simple solution is to apply the water more slowly using lower-rate sprinklers or running several shorter cycles in place of one longer cycle. Wetting agents will not hasten the movement of water into the soil.
Raised Beds: Many home gardeners are growing vegetables in raised beds. They fill the beds with their own blend of soil and organic matter or a commercial mixture, both usually containing a high percentage of organic matter. These mixes have a tendency to resist wetting when dry. The application of wetting agents suitable for use with food crops can help make wetting dry mixes easier.
WSU recommends using a sandy landscaping fill comprised of sand and compost or other organic matter in WSU Extension FS075E “Raised Beds”.
Thatch: If a lawn with an appreciable layer of thatch dries out, the thatch may resist rewetting and hinder the movement of water to the roots below. This creates dry spots even in places where adequate water has been applied. If this is the situation, the application of a wetting agent and core aeration can help water move through the thatch and into the soil.
If you are faced with a situation where wetting agents may help, there are several home garden products available, including Scotts Everydrop Counts, Safergro Natural Wet and Monterey Perc-O-Late Plus.
Marianne C. Ophardt is a retired horticulturist for Washington State University Benton County Extension.