Soil wetting agents are often used on sandy or very dry soil to help water penetrate it more fully. These agents break down the molecules in the soil very slightly, making the ground more receptive to water and eliminating dry spots. When choosing an agent, one must usually sift through dozens of different kinds. Gardeners trying to select one should typically consider how long the formula is supposed to last, what kind of soil it calls for, and the agent’s strength. After that, it may take some trial-and-error before the gardener discovers the perfect wetting agent.
Wetting agents come in many different styles of time-release formulas. Some formulas are supposed to last up to three months, while others require reapplication after only a week or two. Gardeners living in very warm climates that deal with consistently dry soil should generally opt for a wetting agent that lasts a few months. Those dealing with occasional droughts and thawing spring soils may look for agents that require weekly application. This allows the gardener to use the wetting agent only when necessary.
The second factor gardeners should consider is the type of soil a wetting agent is formulated for. Some agents are made specifically for sand, while others work better on clay. The label on a formula's container usually state this information, or at least give suggestions.
If the label doesn’t include soil suggestions, it may state the formula’s strength. Very sandy or clay soils — soils that almost never absorb water on their own — may require very high strength formulas. Hard-packed loam and soils dried out from drought or winter frost may only require a low- or medium-strength wetting agent before they start absorbing soils on their own again.
Testing wetting agents before applying them to an entire lawn or garden may save users a lot of frustration. Typically, spraying some wetting agent on just a square foot of the problem area will tell a gardener whether or not the formula is correct for the location. Soils treated with the proper wetting agent should feel moist and clump together when pressed between the fingers. Plants should sprout and grow without turning yellow or showing signs of disease.
Soils that feel soggy after application may require a weaker formula. Conversely, if the soil still feels dry after application, the formula may need to be stronger. Testing the wetting agent usually helps a gardener avoid trial-and-error disasters while also narrowing down which formula may work the best.