Making Water Wetter

Have you ever noticed that water, when applied to some areas, is not readily absorbed, but beads up on the surface and rolls off? On turf, this might be more recognizable by the lush green in some areas while in others it is scorched and brown. You try deep watering with the hose, and instead create a huge puddle that is sending water running off everywhere except the area that you’re trying to take care of. Now you’re wasting water, time, and of course, your patience.

You’ve discovered that even when water actually does seep in the soil, it dries out far quicker than it should, indicating that it’s not retaining the water long enough for the roots to take in enough moisture. With summer approaching, the heat combined with the poor soil is already making the situation worse. The results of this are not exactly the best advertisement for your profession. The problem is the soil’s hydrophobia: meaning its tendency to repel water. Although more of a problem in coarse sandy soils, hydrophobia can be present in many different soil variations; providing ample opportunity for landscape related headaches. Typically, the only way to counter this soil’s tendency to repel water was simply to deeply water the area; eventually, after using more water than necessary and producing a small flood, the ground would relent under the pressure and soak some down. To make matters even worse, even when the water goes into the soil, the problems don’t end. Macropores in the soil, commonly caused by worms, roots, and from the soil shrinking and swelling, takes the water in the hydrophobic soil, prohibiting the water from being distributed evenly. Since water cannot move through the water repellent soil, water clusters form in these macropores that become heavier as their added mass attracts more gravity. This accelerates the water flow through these channels, and takes the water (along with any fertilizer, pesticides, etc) quickly past the root zone of turf and plant material before they are able to effectively absorb it. As a result, turf and plant quality is affected, while simultaneously increasing the risk of contaminating groundwater reservoirs.

In a well-tilled area with a good soil mix the soil absorbs water readily and these macropores don’t present a problem. Water will seep consistently down and spread where you want it. In poor soil, because water will travel the path of the least resistance, these pores are often directing water in a different direction than you want it to go.

Care to know just how hydrophobic the soil is? A quick way is to place a few droplets of water on the soil in question. If the droplet doesn’t absorb into the soil in less than five seconds, you’re working with hydrophobic soil.

Sellers of surfactants, wetting agents, or soil penetrants are trying to resolve the above stated problem. They make water wetter. “Surfactants make the soil absorb water,” says Colleen Clifford, marketing manager for Aquatrols in Cherry Hill, New Jersey. “Water is lazy, and will take the easiest path, which can sometimes be quite a distance away from where you are trying to water. Water repellence is a bad thing; a surfactant combats that.”
“Basically, what these surfactants will do is make poor quality soil have the water absorbing characteristics of a pristine soil,” says Clifford.
Water flow before and after surfactant treatment

Sometimes, contractors inadvertently make the soil hydrophobic by having good intentions; such as using bark mulches for moisture retention. “When you use bark mulches, you’re inadvertently making the soil more hydrophobic. It will help with keeping the soil moist, but bark is naturally water repellent,” says Colleen. “Wetting agents and surfactants help get the water to soak through that and keep the bark from spreading the water away from the turf or plants you’re trying to take care of.”

At a time when most of the country is either in a drought or close to it, water conservancy has certainly become more than just a buzz word. Some counties have mandates that only permit yard watering on specific days for a certain amount of time, and officials are beginning to crack down on violators with heftier fines. In these areas where water conservation is not only a fleeting aim but absolute law, it’s imperative to get as many drops of water to work for you as humanly possible. Surfactants can help you to do that.

“If the right soil problem exists, surfactants can really help with irrigation efficiency,” says Keith Karnok, professor of turfgrass science in the department of crop and soil sciences at the University of Georgia and long time researcher of soil surfactants. “In certain soil conditions, studies have shown between 20% to 40 % in savings of water.”

If you look at the array of different wetting agents available, confusion may be what’s really soaking through. Different wetting agents are available to do different things. Some products offer long term coverage, some are engineered to be distributed slowly but frequently through the irrigation system. Depending on the particular soil problem you’re experiencing, one particular surfactant may perform better in a given situation and be better suited than another.

Let’s say the yard you’re having some trouble with isn’t all that bad. You’ve simply noticed some localized dry spots and you don’t feel you have a particular need to treat the entire area. There are wetting agents available for this kind of spot treatment, specifically geared toward localized dry spots, which can be considered a cost friendly alternative if the rest of the soil is in pretty good condition.

There are also soil treatment surfactants available that are engineered for monthly treatments and even programs for yearly douses. However, some professionals in the industry feel the best results are obtained when the surfactant is applied at a small amount at more frequent intervals.

An efficient way of doing this would be to apply a surfactant through a fertigation unit. The surfactants are compatible with fertilizer and would make surfactant treatment as convenient as automatically fertilizing the lawn. One such company offering this treatment is FertiGator.

“The testing data at multiple universities make it pretty clear the best results are obtained when the soil surfactants are applied frequently with a lighter dosage,” says Dave Cross, marketing manager with FertiGator, St. Louis, Missouri. “Because of this, the surfactant can be easily mixed with the fertilizer in the tank, shake it up, and that’s it: you’re done.”

In one study at the Fort Lauderdale Research and Education Center at the University of Florida, tests concluded that “applying the low rate of either material (surfactant) on a more frequent basis would be the best strategy for obtaining the highest turf grass quality during periods of severe moisture stress and high evaporative demand.” They also discouraged applying large amounts, saying “an endorser would not benefit greatly by using the higher rate less often.”

“As landscape contractors become savvier with the technology and innovations available for landscape management, surfactants are increasingly becoming more of a commonly accepted tool,” said Clifford.

Soil wetting agents have also improved since their debut. They are no longer nearly as phytotoxic, as in being toxic to plants, as they used to be, some are not toxic at all.
Surfactants may be applied at any time of year and on any kind of current soil condition. “You don’t have to start a program using surfactants when the ground is wet,” says Cozette Hadley, business unit manager for Becker Underwood, with headquarters at Ames, Iowa. It is recommended that you water for an average of ten minutes after application to get the surfactant off the plant material and into the soil.

The method of applying the surfactant is more or less up to the contractor’s preference. Granular forms are available to be used in a spreader as well as in liquid form for use in sprayers. Whatever the contractor’s needs are, the odds are there is a surfactant in a preferred form for your application.

However, as with most things in a landscape contractor’s toolbox, wetting agents are not a miracle pill. They are not designed to replace fertilizer or responsible watering. They should be regarded as another tool to help the plants go greener and the water go farther. Karnok recommends the contractor understands what the problem really is with the soil before choosing to use a wetting agent.

Karnok advises the contractor to follow some common sense guidelines when applying a wetting agent. “Read and follow the label to the letter. If it says to apply the product every thirty days, then apply it every thirty days. More is not better. Do not double up. If you have any questions, contact the manufacturer.”

As water conservancy becomes more important, surfactants definitely have a place in the green industry for its ability to do what sounds absurd: the power to make water wetter.

JULY 2004