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The Role of Ice in Winter Injury

The Role of Ice in Winter Injury 600 600 Angelique Crosnier


Ice Cover Injury

Intermittent ice formation on golf greens and fairways is a common event in northern Europe. Ice cover is often considered part of winter injury caused directly by a continuous ice cover or as part of freeze injury (low temperature kill).

Ice in Association with Freeze Injury

In areas where continuous ice cover for over 45 days is unlikely due to winter weather patterns being broken due to intermittent periods of thawing, ice formation can play a role in freeze injury. Under this scenario a rapid drop in temperature resulting in freezing water around the growing point during late winter or early spring can cause freeze injury primarily to Poa annua.

The critical precursor to freeze injury is the loss of cold hardiness through dehardening and subsequent rehydration of the annual bluegrass crown region. Continuous ice covers as previously mentioned contribute to the decline in cold hardiness. However, the most important factor regulating dehardening is temperature(5). In annual bluegrass the dehardening process can occur quickly when soil temperatures exceed 46F (8C) for 48 hours(6).

What cultural practices can be instituted to minimize ice injury and/or freeze injury? A thorough discussion is found in the 2004 November/December issue of the USGA Green Section Record in an article entitled “Winter Damage” by Keith Happ. Some of the key points are:

1) Produce a healthy plant going into the winter. A weak Poa annua plant with low carbohydrate storage is not going to tolerate ice cover or be resistant to freeze injury as a healthy plant. Shaded areas are more prone to freeze injury than sunny areas, probably due to the carbohydrate status of Poa annua(7).

2) Eliminate poorly drained areas. Poa annua growing in areas where water accumulates is at high risk to rapid freezing during freeze/thaw cycles.

In conclusion, winter injury is normally a combination of several factors one of which is ice cover. A continuous ice cover can cause injury on Poa annua after 45 days. The formation of ice during freeze/thaw cycles in late winter can create a situation where excessive water in and around Poa annua crowns can create freeze injury from ice formed by a rapid drop in temperature.

Continuous Ice Cover Injury

The first type of ice injury is the direct result of a continuous ice cover often referred to as freeze smothering. In the early to mid 1960’s Jim Beard conducted controlled laboratory study where he looked at the survival rate of three cool season turfgrasses under a continuous ice cover and two turfgrasses under field conditions(1,2). He found that creeping bentgrass could survive 120 days of continuous ice cover, however annual bluegrass (Poa annua) loss occurred after 60 days with substantial loss around 75 days. In a more recent Canadian field study annual bluegrass and creeping bentgrass turf was subjected to 45 days of continuous ice cover and then the ice was removed. Seventy-five days after initiating the study and 30 days after removing the ice cover creeping bentgrass still maintained its cold hardiness, while annual bluegrass was dead(3). It would appear from this study that annual bluegrass under a continuous ice cover needs to be removed prior to 45 days.

The reasons commonly proposed for ice injury are the buildup of toxic gases and/or the development of anoxic conditions, and the loss of cold hardiness. It appears that carbon dioxide (CO2) accumulation under ice cover is a major contributor to the death of herbaceous plants(4). Intermittent thawing helped eliminate the CO2 buildup and injury to the plants in this study did not occur(4).

The loss of cold hardiness under ice cover occurs and varies among turfgrass species. Under continuous ice cover annual bluegrass loses its cold hardiness, while creeping bentgrass is not affected(3). The loss of cold hardiness in annual bluegrass is likely due to the anoxia (lack of oxygen) conditions that develop under an ice cover(3).

1. Beard, J.B. 1964. Effects of ice, snow and water covers on Kentucky bluegrass, annual bluegrass and creeping bentgrass. Crop Science 4: 638-640

2. Beard, J.B. 1965. Effects of ice covers in the field on two perennial grasses. Crop Science 5: 139-140.

3. Tompkins, D.K., J.B. Ross, and D. L. Moroz. 2004. Effect of ice cover on annual bluegrass and creeping bentgrass putting greens. Crop Science 44:2175-2179.

4. Freyman, S. and V.C. Brink. 1967. Nature of ice-sheet injury to alfalfa. Agronomy Journal 59:557-560.

5. Tompkins, D.K., J.B. Ross, and D.L. Moroz. 2002. Dehardening of annual bluegrass and creeping bentgrass during late winter and early spring. Agronomy Journal 92:925-929.

6. Tompkins, D.K, C.J. Bubar, and J.B. Ross. 1996. Physiology of low temperature injury with an emphasis on crown hydration in Poa annua L. and Agrostis palustris. PTRC Report. web site: http://ptrc.oldscollege.ab.ca/researchreports.html

7. Rossi, F.S. 2003. New light on freeze stress. CUTT 14(3): 1,4

Preventing Black Layer

Preventing Black Layer 600 600 Angelique Crosnier


The lack of air circulation in the soil reduces oxygen, which can be very detrimental to the soil profile and consequently affect negatively the turf health.

The black layer is often a symptom of anaerobic soil conditions, usually appearing in high sand content soil, and just as the name implies, it is a horizontal black stratum formed in rootzone at a depth of 1.3 to 10 cm. It causes a reduction in several elements that are essential to the survival of plants. The colour black is the result of a reduction of iron, and the hydrogen sulphide that occurs on the black layer is responsible for an unpleasant smell that helps on the identification of the problem.

There are several factors that may result in the lack of oxygen and poor infiltration rate in the soil such as compaction, excessive organic content layer, excessive sulphur and high sodium additions or any layering that occurs in the rootzone that impedes water movement. Problems characterized as abiotic are not caused by living organisms, but by other factors such as edaphoclimatic conditions, intensity of traffic, inadequate use of chemicals and improper use of the maintenance machinery.

When the soil becomes anaerobic the solubility and chemistries of the nutrients modifies, certain elements are more available for the plant and others become toxic. The lack of O2 promotes the development of anaerobic microorganisms that produce metabolites that can be unfavourable to the development of the plants, such as sulphide (H2S) and iron sulphide (FeS). The black layer may become most evident during prolonged periods of hot humid weather and usually algae is also observed in conjunction with the layer, aggravating the surface sealing that may occur.

The lack of oxygen in the rootzone causes the reduction of the capacity of absorption of nutrients and water causing severe root decline, weakening the plant and diminishing its resistance to disease, wear, heat and cold tolerance.

To prevent Black Layer, it is important to apply topdressing material with similar physical characteristics to the existing on the rootzone and to use only slow release fertilizers or to fertilize lightly and frequently, but the best way to manage the black layer is preventing anaerobic conditions by improving water drainage and coring. The SubAir system is a good option to prevent the problem as it is designed to improve aeration, providing fresh air direct to plant roots and stimulating microbial activity. Also, it stabilises water delivery to the root system and removes harmful gases such as Carbon Dioxide, Methane and Hydrogen Sulphide.

Lack of air movement and high temperatures on turf

Lack of air movement and high temperatures on turf 600 600 Angelique Crosnier

The problem with lack of air movement and high temperatures on turf

There are hundreds of turf varieties out there, but no matter how strong, they are all susceptible to suffer from heat stress.

When we talk about the subject it is easy to believe that it is a problem limited only to the southern areas of the world, but truth is that cool season grasses can suffer even during mild weather, once that on sunny days canopy or leaf temperatures can be 9°C higher than the environment temperature, depending on the soil characteristics. Bentgrass for example, has a net energy loss when soil temperatures rise above 30°C, so if the sun is high and the air temperature is above 21°C, which can happen even in northern parts of England, we could see some loss of functionality of both roots and leaves of the plant.

When a green’s subsoil temperature reaches high levels, grass roots begin to shrink, root growth rates decrease, turf begins to thin and large patches of brown or white turf begin to appear until the plant dies. The cause of death is a process called “denaturation”, which is the destruction of enzymes situated inside the plants cells by the heat.

The lack of air movement will cause stress not only for the plant but also the grounds keeper. Whether in a pocketed green surrounded by trees, or in a stadium pitch enclosed by bleachers, air is a major factor limiting turf health. If grass is not transpiring correctly, it will not be able to cool itself down, reducing the plant physiological abilities to recover and increasing the susceptibility for diseases. Let’s also remember that dew and humidity allowed on the sward for prolonged periods is a strong factor for the development of algae issues.

Heat stress and Summer Bentgrass Decline (SBD) used to be great concerns on turfgrass management before the use of turf fans.

What is a turf fan?

There are different types of turf fans and they have evolved considerably since they first started being used on sports fields. Caged, oscillating, or turbo are the most common ones observed, oscillating being considered the most beneficial for turf care. They have been developed to provide good airflow on the surface. The wind blowing on the grass helps the evapotranspiration process, cooling down the canopy and reducing soil temperatures, keeping humidity controlled and drying out excess moisture.

Quiet and easy to assemble, turf fans can be portable and are usually painted dark green colors to blend in with the environment; Thus, noise and appearance factors are kept to the minimum. Very energy efficient, electrically powered or where no power is available, gas powered, to fight the stresses of heat and lack of air movement in any situation. The fans are steel and powder-coated to help them withstand the elements.

How turf fans improve turf health?

Simply by improving air circulation!

Better air exchange benefits the grass in several ways. Blowing air on the surface controls excess moisture reducing the number of consecutive hours of leaf wetness and increasing evapotranspiration, avoiding fungi diseases and algae problems. Fresh air passing over the turf canopy makes needle tinning much more effective. It also diminishes heat stress lowering both canopy and soil temperature. Not only does the surface benefit but also the rootzone, as moisture can be reduced by 10%. The physiology of the plant will be improved, maximizing fungicide performance, thus reducing the number of applications, saving money and providing a more sustainable environment.

Turf fans have helped grass to survive shaded and warm environments all over the world, making a major impact on sports fields and working as a magic pill for groundsmen headaches.

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