Why wetting agents are so essential for golf green management

Dry patch can be devastating during summer months.

March 14, 2017
5 mins
Dr Andy Owen
ICL Turf & Landscape International Technical Manager

We all know how devastating the development of Dry patch (or localised dry spot – LDS) can be on the performance of golf greens during dry summer months.  If allowed to develop, the turf quality deteriorates in affected areas, localised areas become hard and unreceptive and the overall performance of the greens can become totally unacceptable. To combat such deterioration the use of wetting agents has been widely adopted over the last 25 years. The aim of this article is to provide a refresher on why wetting agents are so essential for the management of golf greens these days. 

It is important from the outset, to distinguish Dry patch from drought stress.  For clarity, Dry patch is a condition of the soil whereas drought stress is a condition of the turf.  Dry patch occurs when a soil dries out and then becomes impossible to rewet with just water. It is characterised by the soil becoming water repellent. The development of this water repellency is related to soil-borne fungal activity and also due to the natural breakdown of organic matter in the rootzone as a part of the decomposition process.  

Plant drought stress is different from soil water repellency in that it is the reaction of the turfgrass to insufficient water availability. This may be brought on by a number of additional factors such as poor irrigation coverage, poor rooting, species characteristics and it can be heightened by the intensity of maintenance, wear as well as climatic and site conditions etc.  Drought stress adversely affects the functioning of the turf and it might lead to a deterioration of the turf directly or through the secondary impact of damaging diseases that might take advantage of the situation.  Our tactics to prevent or overcome drought stress might involve the treatment of soil water repellency but will also deal with plant health, maintenance and irrigation issues also. 

So, let’s focus on the development of Dry patch for the purposes of this article and why we need to treat the soil with wetting agents to prevent it from happening. 

Research into Dry patch and water repellent soils has identified the presence of water repellent material within the rootzone. These materials are waxy hydrophobic compounds that attach to sand particles within the rootzone and render it water repellent.  This can be quite localised through the profile with water repellent layers existing in amongst unaffected areas. If we compare sand particles taken from a hydrophobic region with sand from a “healthy rootzone” under an electron microscope, the organic deposits stuck onto sand grains can be seen where the sand is hydrophobic whereas this is notably less in unaffected areas.   

The origin of these waxes that are seen to be coating the sand grains is probably not attributable to any single cause.  However, there is strong evidence that previous fairy ring activity could be one factor, and sometimes dry patches on golf greens can be seen in rings across the surface similar to old fairy rings.   Also, when turf cores are taken from active fairy rings and incubated in moist conditions, the fungal mycelium grows out from a layer in the core which corresponds to the layer in which the most hydrophobic sand is seen (Figure 4).   

Incubated turf core showing fairy ring mycelium . Note no mycelium present in surface or deeper rootzone. 

Figure 4

Linking Dry patch formation to Fairy ring activity and the production of water repellent substances by Fairy ring fungi certainly fits with greenkeeper experience but it must be remembered that this is probably not the full story.  Water repellent soils exist in agriculture and natural grasslands where Fairy rings have not been recorded. In these cases the buildup of water repellent materials has come from the production of organic acids created as a result of the natural thatch decomposition processes.  It is likely that there is a range of factors that contribute to the accumulation of water repellant material in the soil profile. 

So, what can be done to prevent and control Dry patch? The first step is to identify the primary cause. Is there an actual hydrophobic layer present – or is the turf just drought-stressed?  The irrigation system should be checked and moisture meter used to adjust water inputs, cultural practices should also be employed to try and develop a deep turf root system, and alleviate any potential compaction. Symptoms of stress could be an indication of a wide variety of issues that need to be attended to. 

However, if a water repellent soil is present and this is likely in many cases then this will need to be addressed directly.  There are cultural approaches which will help to mitigate the situation. Thatch reduction will limit the development of Fairy rings.  Coring and topdressing with suitable materials will also help replace water repellent soil with fresh material.  Cultural management will help reduce the propensity of a soil to become water repellent but it will not totally prevent it from occurring if soil moisture levels aren’t managed properly. 

The immediate solution to preventing a soil becoming water repellent is to use wetting agents.  This approach has become standard practice in modern greenkeeping and the best materials are extremely effective.

Wetting agent technologies have evolved significantly over the last 20 years with research by Universities and specialist laboratories leading to the production of highly active wetting agents that offer truly effective treatment for Dry patch. The very best products utilise blends of surfactants that can allow water to penetrate and be held within a soil that would otherwise repel water. Reputable manufacturers spend a great deal of time and effort to develop effective materials and they conduct extensive trial programmes to demonstrate the performance of their products. It is important to use trusted specialist suppliers that can demonstrate the performance and quality of their products against Dry patch.  Check the research, and select the right one for your situation. Remember a programmed approach of wetting agent application, which starts early in the season will provide the best results – you are best taking a preventative approach.  

So, Dry patch is a potentially damaging soil condition that can radically impact on the performance of golf greens.  There are some cultural measures that can reduce the risk of it developing but modern wetting agents can offer an immediate solution. There are a wide range of wetting agents on the market and it is important that you select your chosen product based on trustworthy R&D work and use it preventatively to ensure that you get the best results.