As turf agronomists a common question is “what is the best wetting agent for soil and turf in Australia?” This blog discusses soil wetters and what is the best wetting agent for lawns and turfgrass but before we can answer this we need to define what exactly one is.
What are soil-wetting agents?
A soil-wetting agent is “A compound that causes a liquid to spread more easily across or move into the surface of a solid by reducing the surface tension.” Spray adjuvants use this principle to increase chemical contact with a leaf.
Several wetting agents for lawns and sportsturf claim to be the best soil wetter. These all work (to varying degrees) by countering hydrophobic (water-repellant) soils.
They help to increase uniform water movement through the soil profile, which means you use less water to give a more consistent surface. Our recent 2022/2023 work on soil-wetting agents shows how soil wetters can vary. We have also looked at the impact of soil wetters on soil organic matter.
Why use wetting agents?
There are four main reasons to use these:
1. For localised dry spot treatment;
2. To improve your water use efficiency;
3. To move water away from the soil surface and
4. As an aid to help chemicals move into the soil.
Sand-based soil profiles are difficult to manage at the best of times. However, in dry, hot conditions, ‘hot spots’ can develop that dry out faster compared to other areas. The best soil wetting agents for lawns and turfgrass, help reduce surface tension and aid uniform water movement into the soil.
Australian Research into Soil Wetting Agents – 2023/2024
The results below are the first part of a long-term soil wetter study looking at their performance in turfgrass health and water droplet penetration time at three depths.
The trial was a replicated block of 10 treatments in 6 blocks in a bentgrass green at Bonnie Doon Golf Club in Sydney, Australia.
Products tested were:
- ICL TC
- HK
- TT Respond 3
- TC
- Hydroforce Ultra
- TT Respond 2
- P
- Control
- Proprietary formulation with claimed plant health benefits
- TT Respond 1
Treatments were at label rates. Three weeks after the product was applied, plugs were taken and then air-dried for 2 weeks. So all treatments went two weeks with no water.
Turfgrass Health
It is all very well getting water into the soil, but does it remain available to the plant?
We tested this visually and with a TDR 350 to measure the soil moisture after these two weeks.
All treatments had only been applied once before drying. We then took plugs three weeks after treatment. The images below are the cores taken after being air-dried for two weeks.
All treatments apart from Hydroforce Ultra (Treatment 5) had a 1-2% moisture content. Hydroforce still had a VMC of 6%, which may help explain the results below.
Images were taken at this stage comparing the turfgrass appearance. As a guide, the control (Treatment 8) was pretty much “flamed”.
I don’t think it takes a rocket scientist to see that Treatment 5 (Hydroforce Ultra) outperforms all the others in this test. Those treated with Hydroforce Ultra continued to grow despite the water being cut-off.
Water Droplet Penetration Test
Water Drop Penetration testing (WDPT) was carried out at 1cm, 2cm and 3cm. All the cores appeared to be highly hydrophobic, so this was a pretty extreme test of how these perform.
The results of the WDPT are below.
Discussion of 2023/2024 Results
There are differences in how these perform. ICL TC, Hydroforce Ultra and the proprietary blend all have excellent initial wetting to counter surface hydrophobicity due to thatch. HK and TT Respond 1 really struggle. A possible reason for this is that they could run out of steam after three weeks.
At the 2cm depth, differences still existed and, HK again struggled. Standout performers are ICL TC, TT Respond 1, TC, Hydroforce Ultra and the proprietary mix.
With the results at 3cm, this is a real test for these. The soil is very hydrophobic, so this is a good measure of the ability of these soil wetters to get water down to depth. The proprietary mix, Hydroforce Ultra and TT Respond 3, all perform well. However, ICL TC does not give that deep water penetration the others managed.
This work raises the question of plant availability of water in the soil. A soil wetter may well move water uniformly into the soil and through the rootzone, but if it isn’t available to the turf is it actually doing the best possible job?
The only one in this trial that appears to be doing this is Hydroforce Ultra.
During this trial, we will also take moisture readings at 37 and 75mm over the duration. At its end, we will do a root assessment to see how these soil wetters affect root growth.
This work raises the question of plant availability of water in the soil. A soil wetter may well move water uniformly into the soil and through the rootzone, but if it isn’t available to the turf is it actually doing the best possible job?
The only one in this trial that appears to be doing this is Hydroforce Ultra.
During this trial, we will also take moisture readings at 37 and 75mm over the duration. At its end, we will do a root assessment to see how these soil wetters affect root growth.
Overseas Trial Work
The following are some independent trial work on cool-season bent/Poa annua fairways. These results are also relevant to what is the best wetting agent for lawns. Hydroforce® Ultra in a trial vs Dispatch® (Aquatrols) and an untreated control. Throughout the trial Hydroforce® Ultra consistently:
- Improves and maintains turf quality;
- Increases soil volumetric moisture content (VMC %).
Hydroforce® Ultra gives results on greens.
A US study in 2021 on a mixed Poa/V8 bent green. Hydroforce® Ultra used at 13L/Ha; Pervade® (Floratine) at 6.4L/Ha. Results show:
- Less dry spots compared to the Pervade® treatment or the untreated control;
- Hydroforce® Ultra gives more consistent moisture levels;
- Up to a 30% increase in root mass and
- A reduction in the need to hand water.
The video below shows Hydroforce® Ultra on a golf course fairway in the UK.
This video is from Ludlow GC in the UK, and shows how water rapidly moves away from the surface after treatment with Hydroforce Ultra. In the UK, Hydroforce Ultra is marketed as Prowet Evolve®.
Research into soil wetting agents
Any recommendations we make are supported by good science. The pdf below shows the results of a soil wetter trial we completed in 2019 at Bonnie Doon GC in Sydney, NSW.
2019 Sydney soil wetting agent trial summary
2022/2023 Soil wetting agent trial at Bonnie Doon GC, Sydney.
This is more work into the best soil wetter for turfgrass, and the best wetting agent for lawns. We looked at volumetric moisture content, surface hardness and turf health.
2022/23 Sydney soil wetting agent trial summary
Improving turf nematode control.
The best soil-wetting agent for lawns and turfgrass doesn’t just manage your water better. It also has added benefits such as helping to control soil nematodes. Treatments were as follows in this nematode control in couch grass study:
- A mixture of the nematicide abamectin and the wetting agent Hydroforce® Ultra;
- Abamectin by itself, and finally
- Hydroforce Ultra soil wetting agent as a stand-alone treatment.
Results were:
- Hydroforce® Ultra plus abamectin provides the best control and
- The stand-alone treatment of Hydroforce® Ultra gives better turf quality than the nematicide by itself.
Hydroforce® Ultra results in more efficient water use and uniform distribution into the soil profile.
FAQ
Do wetting agents retain water or help it penetrate into the soil profile?
The first wetting agents were used to help water move into the soil profile by reducing surface water repellency and hydrophobicity. Many were excellent at doing this but caused turf damage if not watered in immediately.
Over time, soil-wetting agent chemistry has improved so that soil-wetting agents not only help water move evenly through the soil profile but have plant health benefits.
The soil chemistry of any wetting agent will influence how it performs. For example, in a US study of 15 wetting agents, a modified polysiloxane gave the lowest surface tension, and reduces the water surface tension to a third of tap water! Examples of this include Consume® and Scrubwet penetrant®.
Our 2023/2024 wetting agent trial is giving some interesting results. Most products retain moisture in the soil profile compared to the untreated control.
Does soil wetting agent need watering in?
Soil wetting agents work in the soil, so you need to water them in. The question should be do they need to be watered in immediately? Ideally, they should be watered straight after application. However, our ongoing soil wetting agent trial has shown that if these are applied as per the label they are very unlikely to damage turf. To further increase turf safety certain products are formulated to have an increased level of turf safety. HydroForce Ultra uses an innovative block polymer technology that offers great turf safety. We still recommended irrigating after application to move the product into the root zone but as long as it’s not a hot day it doesn’t have to be straight away.
Are all wetting agents the same?
Due to differences in formulation soil wetting agents differ in their effects on water infiltration, retention, and ability to reduce surface tension. For example, recent wetting agent trials have shown that there a big differences in their ability to retain soil moisture, effects on surface hardness, disease incidence, and turf quality.
Graph showing how soil wetting agents can differ in their effects on soil moisture. Treatment 6 is the untreated control
How different soil wetting agents can affect turf quality. Treatment 2 which is HydroForce Ultra, shows an increase in turf quality following multiple applications
All treatments apart from the untreated control (6) gave a softer surface
Regular use of newer soil-wetting agents like HydroForce Ultra gives less turf disease. In this instance less brown patch
How long do soil wetting agents last?
The two main factors influencing this are their chemistry and environmental conditions. Some are marketed as only needing to be applied once-a-season and claim to last up to three months. The issue that we have with this is that you don’t know when they stop working so it can lead to periods when effectively no wetting agent is present. If a soil wetting agent lasts a month and you apply on a regular basis then you avoid these issues developing. Always ask for independent data to support any claims made rather than relying on a glossy brochure.
Why do some soil wetting agents burn grass and cause damage?
Soil-wetting agents break the surface tension of water and help water move through the soil profile. However, their composition differs from most surfactants. Nonionic surfactants are the basis for many of these, and then mixed with polyoxyethylene esters, or ethoxy sulphates.
Apply these at too high a rate or too high a temperature, and they can cause membrane permeability problems. This results in the death of roots and leaf tissue. Some surfactants dissolve cuticle/wax layers on the leaf blades and cause discoloration and burning if allowed to stay on the leaf surface too long.
Soil wetting agents like Hyroforce Ultra soil wetter contain no harmful chemicals that can cause turf burn. However, as with most things, if you apply any chemical when it’s blistering hot and don’t follow the label, you are asking for trouble.
Our 2023/2024 soil wetting agent trial has found some interesting results on the impact on turf quality when you don’t water some products immediately. Some are perfectly safe, and others caused a temporary discolouration of the turfgrass.
Can I use washing up liquid as a soil wetting agent?
Of course you can but we don’t recommend it. If you use ordinary washing-up liquid as a soil-wetting agent it will at first give a short-term improvement in water penetration into the soil. However, in the long term, the effects are detrimental to wildlife and the soil itself.
- Many household detergents contain high phosphate levels which can wash into our drains and streams;
- They can be very phytotoxic to plant material;
- Long-term detergent use destroys the soil structure and increases salt levels
Disclaimer
All information is provided by Gilba Solutions Pty Ltd. While we endeavour to keep the information up to date and correct, we make no representations or warranties of any kind, express or implied, about the completeness, accuracy, reliability, suitability or availability with respect to the website or the information.
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Graduated from Newcastle University with an Hons Degree in Soil Science in 1988, Jerry then worked for the Sports Turf Research Institute (STRI) as a turf agronomist before emigrating to Australia in 1993.
He followed this by gaining a Grad Dip in Business Management from UTS. He has worked in a number of management roles for companies as diverse as Samsung Australia, Arthur Yates and Paton Fertilizers.
He has always had a strong affinity with the Australian sports turf industry and as a result he established Gilba Solutions as an independent sports turf consultancy in 1993. Jerry has written over 100 articles and two books on a wide range of topics such as Turf Pesticides and Nutrition which have been published in Australia and overseas.