Wetting agents are part of many greenkeepers’ toolbox, especially on sandy soils and in summer, when dry patches appear that water refuses to penetrate. Used well, they improve infiltration, reduce hand watering and prevent stressed areas. Used badly, they are one more expense that masks an underlying problem.

Before thinking about the product, it pays to understand what happens in the soil. These five rules help you decide when it makes sense to apply wetting agents, how to integrate them into irrigation management and how to check that they are working, always respecting the label and current regulations.

Rule 1: Diagnose Before Applying Wetting Agents

A dry patch is not always water repellency. It can be due to a coverage failure in the irrigation, compaction, disease, shallow roots or a crooked sprinkler head. Applying wetting agents without a prior diagnosis treats the symptom and leaves the cause untouched.

A few simple tests help tell the difference:

• Drip water onto the dry soil: if it takes time to penetrate and stays in beads, there is repellency.
• Take a core and check whether the profile is dry underneath while the surface looks moist.
• Check irrigation uniformity with catch-can tests in the affected area.

Note where the patches appear each season. If they are always the same, they probably relate to soil type, organic matter or exposure. High points, green edges and areas with lots of afternoon sun are usually the first to dry out, and it pays to check them first thing in the morning, when the difference between wet and dry leaf is easiest to see.

Rule 2: Understand What Wetting Agents Do

Wetting agents are surfactants that reduce the surface tension of water or modify the surface of soil particles, so that water penetrates more easily and spreads better through the profile. That is the theory; in the field, the effects depend on the formulation, the severity of the problem and irrigation management.

• Some facilitate initial infiltration in soils that are already repellent.
• Others serve as prevention and help maintain a uniform profile during the summer.
• Others combine functions, for example helping to retain moisture in the root zone.

It pays to ask the technician or supplier for clear information on the type of product and its intended use, and to compare it with your own experience. Never assume that a wetting agent will solve a problem that has a physical or design origin.

Rule 3: Apply Wetting Agents at the Right Time

Timing of application greatly influences the result. The usual approach is to act before the problem is severe: when the first signs of stress appear in summer or before the months of highest demand, and not when the turf is already dry and burnt.

1. Schedule preventive applications according to the course’s history of dry patches.
2. Avoid applying in extreme heat or full sun if the label advises against it.
3. Irrigate after application if the product says so, to carry it into the root zone.
4. Do not repeat applications without checking the effect of the previous one.

All treatments must follow the label, current regulations and the advice of an authorised technician where applicable. Never increase on your own what the manufacturer indicates. And remember that a good time for application also depends on the course schedule: avoid coinciding with tournaments or hours of heavy play, so as not to interfere with players or walk on the freshly treated surface.

Rule 4: Combine Wetting Agents with Good Management

No product replaces cultural management. Wetting agents work best when accompanied by aeration, thatch control and well-calibrated irrigation. A compacted profile or one with excess organic matter has problems that the surfactant only relieves temporarily.

• Aerate regularly to open channels through which water reaches the roots.
• Control thatch: a dry organic layer easily becomes repellent.
• Adjust irrigation to wet deeply and not just the surface.
• Check the quality of the irrigation water, especially if it is saline or reclaimed.

On courses with sand-based green construction, repellency is a common summer phenomenon, but it can also be greatly reduced with early, consistent management, so that the product is a complement and not the star of the programme.

Rule 5: Measure, Record and Compare Results

To know whether wetting agents work, you have to measure. Without records, every summer will be a new act of faith and spending on product will continue out of inertia.

• Define treated and untreated reference areas to compare objectively.
• Measure soil moisture with a probe before and after, at the same depth.
• Note date, zone, product, conditions at the time and associated irrigation.
• Assess water and hand-watering hours saved compared with previous seasons.

With that data you will be able to decide whether it is worth keeping the programme, adjusting it or dropping it. You will also have arguments to explain to management why it is applied in some areas and not in others, and what consumption has been avoided. A closing comment from the person in charge of irrigation, noting what they would change next year, is worth more than a table full of uninterpreted numbers.

Finally, keep the safety data sheets and labels of the products used, and make sure storage and handling comply with current regulations.

Further reading: USGA. The USGA publishes technical documentation on the construction and management of sand-based greens, useful for understanding why certain profiles tend to repel water.

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