Penetrant wetting agents in summer??

This one popped up on a facebook thread the other day and it got me thinking about a trial we did in 2015 / 2016 at the STRI.

The sub 20% part of the trial

The thread went something like this:

Retentive type wetting agents hold too much moisture leading to more thatch accumulation and actually you should use penetrant type wetting agents to push roots deeper.

We were very interested in the thatch accumulation issue so back in 2015 / 2016 we commissioned a study to understand the impact of Qualibra on thatch / OM accumulation to ensure we were offering good advice.


In this trial

Penetrants in the summer led to lower turf quality and more dry patch. Retentive type wetters increased moisture content when rootzones were dry but didn’t hold them wetter during wet periods.

No differences were seen between any of the treatments when looking at organic matter accumulation.

This does reflect my experience, when managing a golf course, I went through a phase of using penetrants and I spent more time hand watering than I care to remember, the switch to a retentive wetter gave me my weekends back, increased the quality of my putting surfaces and reduced my anxiety levels.

If you use a retentive wetter make sure you continue to monitor moisture content and water effectively. In order to manage healthy turf adequate moisture is required to ensure plant health is sustained. Rootzones that are too dry will not encourage a healthy root system they will only limit it. Turf that sees high levels of moisture stress are also prone to Anthracnose challenges later in the season.

Read on for the trial data…..

Part 1 Turf quality

We effectively ran two trials – one where we tried to hold the untreated at under 20% VMC (Volumetric Moisture content – how wet something is) and one where we tried to hold the VMC between 25% and 30%.

Conclusion 1

When running surfaces dry – retentive wetting agents will help maintain higher turf quality than untreated. Penetrant wetting agents showed a negative turf quality trend although it was not statistically different to the untreated.

When holding moisture levels higher we saw no difference between any of the treatments.

Part 2 Did they alter moisture content?

In one section of the trial we aimed to hold the wettest area of the trial area at under 20% VMC and in doing so applied the same amount of water over that section.

In the other section we aimed maintain the area in the 25 – 30% range.

Conclusion 2

When running greens dry retentive type wetting agents held more moisture than both the untreated and the penetrant wetting agents.

When running greens at high water volumes the wetting agents held no more additional moisture than the untreated or the penetrants. The only product that showed a indication of reducing moisture content at higher levels was a “retentive” type.

Part 3 How Firm?

In this part of the trial we wanted to understand the impact of wetting agents on firmness, this was measured with a clegg hammer.

Conclusion 3

When running greens dry penetrants made no difference to greens firmness but using a retentive wetting agent reduced clegg hammer reading (probably down to the high moisture content shown in previous assessment).

When running greens slight wetter there were no statistical differences but the untreated trended lower than all that were treated with a wetting agent.

Part 4 Do we generate more Organic matter using wetting agents?

We measure organic matter at the beginning of the trial and again at the end. No aeration or renovations were conducted during this period.

Conclusion 4

No statistical differences here at all (so all treatments are effectively the same). We didn’t even see additional organic matter generated in the plots held at higher water volume (which surprises me).

We did see seasonal changes with lower quantities of OM in the May assessment but no treatment differences.

Part 4 How is dry patch impacted by wetting agent use?

In this assessment we want to establish if dry patch was influenced by wetting agents. This was scored on a 1-10 score with 10 being the highest score possible and 1 showing no evidence of dry patch.


When running greens dryer Penetrants show a trend to exhibit more dry patch than an untreated plot.

When running greens wetter there was no difference between all treatments.


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