Dry patch is a recurring phenomenon and, whilst ever you use topdressing, it will continue to be so. Dry patch only grows and will always return to the same place every year!
The use of wetting agents has long been a subject for debate, especially with regard to what they do and when is it necessary to use them. This article will attempt to furnish you, the reader, with the necessary information to make informed choices, how and when to use wetting agents and which one to choose.
We shall explore the background to the problems and the symptoms that require us to use wetting agents.
As wetting agents are about controlling water movement in general, it is important to differentiate between the differing circumstances requiring particular products to be used. By this I mean that wetting agents need not be exclusive to combating dry patch problems, but also to assist with soils that are saturated and stagnant. In order to look at these areas in more depth, and assist in making an informed choice about when to use wetting agents, and which product, it is necessary to look at the causes and symptoms of dry patch conditions, and also wet soils of the autumn and winter periods too.
Although it is increasingly desirable to apply minimal amounts of water to fine turf areas, so as not to encourage thatch, disease and poor quality sward, there is a fine balance between keeping turfgrass on the edge of survival and dry patch. Drought tolerant species such as Fescues (Festuca) and Bent grasses (Agrostis) have certain characteristics that allow them to survive with minimal amounts of both water and nutrients.
However, as turfgrass managers are constantly battling with Annual Meadow grass (Poa annua), it is important that the quality of the surface does not suffer in order to alter sward composition through extreme measures, which requires a certain amount of water to be applied to enable the plant to survive. If the turf manager can apply the necessary amount of water to keep the plant alive, without over compensating, then he/she is well on the way to winning that battle. However, if you are struggling with water penetration and percolation because of dry patch, you will forever be applying more water than is necessary.
In most cases, low water infiltration rates are caused by factors other than water repellency. For example, water naturally moves more slowly into fine-textured (clayey) soils because the soil pores (spaces between the soil particles) are simply too small to allow rapid water movement. Cultural practices that promote good aeration and particle aggregation can improve the infiltration rate on these soils. Heavy, clayey soils are more receptive to a penetrant wetting agent, rather than a residual wetting agent which would need to be applied every 30 days.
Extensive research has been conducted on hydrophobic soils and on the effectiveness of wetting agents. Some of these studies have focused on localised dry spots in turf grown on naturally sandy soils, and on formulated materials high in sand content. These dry spots become a serious turf management problem during the summer months, especially during periods of drought. Despite frequent irrigation, the soil in these spots resists wetting, resulting in patches of dead or severely wilted turf. The water applied wets the turf, but does not adequately penetrate the soil surface to reach the rootzone.
Continual studies of dry spots in turfgrass have found that the hydrophobic condition was restricted to the top one inch of soil. The infiltration rate in the dry spots was only twenty percent of that measured in normal areas. Therefore, a water drop penetration test is always recommended.
Simply take a core, place a pipette of water every one inch from the top of the core down for five inches. If the water stays on the core without dispersing into the profile for five seconds or longer you have dry patch!
Once your core has proved you have dry patch, then you, as the turf manager, can attack the problem based on budget, manpower and severity. The surfactant technologies around today give you many options. An informed choice, after understanding your problem, is your way of combating dry patch.
Residuals, Penetrants and Curatives
Wetting agents can be split into three categories: Residual, Penetrants and Curatives. Residuals keep working over a given stated period, depending on the amount of time you require it to work, but will only mask the dry patch.
Curatives combat the problem of dry patch, but never totally alleviate the problem as, every time you topdress, you add a further layer of dry patch to your turf. One of the lesser known facts is that when using curatives your water consumption can reduce by up to 30% year on year.
Penetrants help remove standing water as well as move water through the profile. Many turf managers use penetrants in a tank mix, when using other chemicals to get the product through the profile immediately.
Whenever tank mixing any product, always prepare a jar test first to guarantee compatibility.
Available today in the marketplace are the following wetting agent technologies:
• 7 day treatments (penetrant)
• 30 day treatments (residual)
• 30 day treatments with added kelp (residual)
• 30 day curative treatment
• 3 applications per season (curative)
• 30 day fairway treatment (residual)
• 90 day treatments (residual)
• 240 day treatments (residual)
Application of use
240 day treatments are generally used on bunker faces, tee areas and high spots.
90 day treatments are used on tee areas.
All 30 day and 7 day applications are generally used on the greens.
Curatives are used on the greens only.
Penetrants: Will stave off the greens burning up over a hot weekend.
Residuals: Will re-wet for a period of up to 7 days, but should not be used as a programme, residual pellets are for emergencies only. Some contain kelp to act as an immediate bio-stimulant hit.
Tablets: To be put in the irrigation system to use on fairways, tees and greens. These are 30 day residual products.
Now you have this information, make sure you don't make your representative's sales target for the month, but that your wetting agent budget is spent on what you want!
About the author: David Goldstone is the Managing Director of Tower Sport (Europe) Ltd. who specialise in many different wetting agent technologies, some of which are mentioned in the above article. He can be contacted at: firstname.lastname@example.org