9 minute read
TECHNICAL INSIGHT
SURFACTANT TRIALS RESULTS REVEALED
Turfgrass surfactant trials data
Soil surfactants, wetting agents, penetrants, wetters. Are they the same thing, what exactly do they do and are they worth the cost and the bother of having to apply them to our turfgrass surfaces?
BY DR JOHN DEMPSEY, INDEPENDENT TURFGRASS RESEARCHER
Surfactants have historically been used to greatest effect in the amenity turfgrass industry. For many years they have been a key component of turf maintenance programmes, used to treat localised dry patch; mitigate soil water repellency; enhance rootzone water delivery, water use efficiency and nutrient access; and improve overall plant health.
The key to the successful use of surfactants is for end users to firstly decide the areas of disease control and enhanced turfgrass growth and health.
I’m sharing results from a couple of studies involving the use of surfactants. I won’t be naming any products, as most of the work was done in confidence, but I will provide some interesting and novel data.
TRIAL OUTLINE
These trials were carried out between May and September in 2020 and 2021. They were based on Poa annua greens at two sites, a USGA specification sand rootzone in Kildare and a traditional soil push-up green in Dublin, both maintained at 5mm cut height using standard management practices. Treatments were randomised with four replications, comprising a range of surfactants and untreated controls, sequentially applied at 14- or 28-day intervals. Assessments included: percent volumetric water content (VWC), normalised difference vegetation index (NDVI), turfgrass quality and wilt/drought stress.
target criteria for their use at their facility, and then to research the technical aspects of available products and determine what they can deliver to help achieve those targets – within budget.
Legitimate surfactant producers and suppliers should have solid scientific research data to support their products’ performance, including data from replicated field trials.
Over the past few years, I have carried out numerous field trials, mostly in the
DETERMINE THE TARGET CRITERIA FOR USE AND THEN RESEARCH THE TECHNICAL ASPECTS OF AVAILABLE PRODUCTS AND HOW THEY CAN HELP ACHIEVE THOSE TARGETS
RESULTS
I gathered a signifi cant amount of data from these trials and this is just a snapshot of some of the more interesting results. 2020 results were heavily infl uenced by exceptionally high precipitation rates through the summer months. The mean VWC at the trial sites was 39.26 per cent, with no periods of extended heat or drying down. So there was no useful data regarding drought responses. Treatment eff ects on the mean levels of VWC were not statistically diff erent over the full trial period.
However, assessments of plant heath – i.e. NDVI and turf quality – showed signifi cantly better results in all surfactant treatments compared with controls. In other words, the 2020 trial period was excessively wet, none of the treatments produced diff erences in VWC, but all surfactants improved plant health and turfgrass quality over the four-month period, as shown in Figure 1.
Environmental conditions for the 2021 trials were better. July was extremely hot and dry, and signifi cant wilting was observed. September was also particularly dry, but no wilting was observed. During July, the surfactant treatments signifi cantly reduced wilting compared with the controls. Athough some performed better than others, statistically they were the same, as can been seen in Figure 2.
Plant heath assessments, in particular turf quality, again provided statistically signifi cant data, supporting the conclusions of the 2020 trial. During the 2021 trials, all surfactants gave rise to enhanced turfgrass quality compared with the controls, as Figure 1 shows.
While all of the surfactants alleviated drought stress,
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they infl uenced soil moisture in diff erent ways. An example of how just two of the surfactants performed compared with the controls during June to September is shown in Figure 3.
Moisture levels in the control plots fl uctuated widely: high VWC in June and August, but extremely low levels during the July and September dry spells.
Surfactant A, however, maintained consistent moisture levels throughout the full trial period, with fewer peaks and troughs. Compared with the controls, moisture levels were signifi cantly lower during periods of precipitation and signifi cantly higher during the dry periods of July and September.
Surfactant D performed similarly to Surfactant A, but had greater peaks and troughs, with moisture levels consistently greater than the controls from July to September.
TRIAL CONCLUSIONS
There were a couple of standout results from these trials. Firstly, surfactant eff ects on soil moisture. When the eff ects on mean moisture levels for both years were calculated, there was no statistical diff erences, but it was how surfactants caused the variations observed in soil moisture content under diff erent precipitation periods that was particularly interesting. All the various surfactants performed with similarity, but with their own idiosyncrasies. Some
FIGURE 1: SURFACTANT TREATMENT EFFECTS ON MEAN TURFGRASS QUALITY FOR 2020 AND 2021. LETTERS INDICATE SIGNIFICANT DIFFERENCES AT p = 0.05
8.00 7.00 6.00 5.00 4.00 3.00 2.00 1.00 0.00 Turf quality Turf quality. Mean of 15 assessments between June and October 2020
a a a a a a b
Surfacant A 7.07 Surfacant B 7.03 Surfacant C 6.93 Surfacant D 6.98 Surfacant E 6.95 Surfacant F 6.90 Controls 6.47
8.00 7.00 6.00 5.00 4.00 3.00 2.00 1.00 0.00 Turf quality Turf quality. Mean of 11 assessments between June and September 2020
a a bc c c bc a
a
Surfacant A 7.46 Surfacant B 7.53 Surfacant C 7.23 Surfacant D 7.18 Surfacant E 7.10 Surfacant F 7.30 Surfacant G 7.51 d
Controls 6.84
FIGURE 2: SURFACTANT TREATMENT EFFECTS OF TURFGRASS WILT AT TWO SEPARATE SITES IN IRELAND DURING JULY 2021. LETTERS INDICATE SIGNIFICANT DIFFERENCES AT p = 0.05
7.00 6.00 5.00 4.00 3.00 2.00 1.00 0.00 Wilt Treatment effects on turfgrass wilt July 2021 – Kildare site
b
a a a a a
Surfacant A 1.83 Surfacant B 2.67 Surfacant C 2.33 Surfacant D 2.17 Surfacant E 2.00 Control 6.33
9.00 8.00 7.00 6.00 5.00 4.00 3.00 2.00 1.00 a Treatment effects on turfgrass wilt July 2021 – Dublin site
a ab
a bc
ab
ab c
d
0.00 Wilt Surfacant A 2.88 Surfacant B 3.13 Surfacant C 4.25 Surfacant D 3.25 Surfacant E 6.50 Surfacant F 4.88 Surfacant G 3.75 Control 8.88
FIGURE 3: EFFECT ON VWC OF SURFACTANTS COMPARED TO CONTROL AT 14-DAY INTERVALS FROM JUNE TO SEPTEMBER 2021
VWC at 14-day intervals from June to September 2021
60.00
55.00
50.00
45.00
40.00
35.00
30.00
25.00
20.00
15.00
VWC% Surfactant A
Surfactant D
Controls
26 Jun 21 10 Jul 21 24 Jul 21 7 Aug 21 21 Aug 21 4 Sep 21 18 Sep 21
maintained higher moisture right though the period, while others caused moisture fl uctuations during drier and wetter conditions.
A second standout result was how sequential surfactant treatments enhanced turfgrass health and quality, even during non-stressful environmental growth conditions. Regarding the factors that were involved in the enhancement, I would surmise better infi ltration. Reduced soil repellency and uniformity of water distribution are important, but also, as can be seen in Figure 3, surfactants allowed for drier rootzones during periods of precipitation and maintained greater moisture during dry periods.
Also, in data not shown here, there was greater retention or availability of nutrients after sequential surfactant treatment. Other researchers have indicated positive results in soil microbial activity following surfactant treatments. So there’s more to surfactants than keeping your soil wet.
From my personal experience (which goes back to clearing the local shop of Fairy Liquid in the 1980s), I would recommend the use of surfactants. Which product is up to the individual user, who should expect producers/ suppliers to share fully researched scientifi c data and decide what they need from their programme and match these needs to the product.
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