Provisioning

Background and objectives

Many of the newer warm-season turf grasses, particularly those developed within the last decade or so, have not been tested under Queensland conditions. Even those that have been grown in Queensland often have not been evaluated against a comprehensive range of other varieties.

Our long-term strategy in planting and growing plots of virtually all the available turf grass varieties at the Redlands Research Station is to develop a more detailed understanding of their growth characteristics, together with their relative strengths and weaknesses under local conditions. This has the following benefits:

• Initial impressions of the adaptation, performance and management (including preliminary herbicide tolerance observations) of different cultivars can be gained through close observation of these plots. These observations can later be critically evaluated against results obtained in replicated trials elsewhere.
• Assembling a comprehensive reference collection of turf grass varieties enables us to choose appropriate genetic material for use in other projects that look more deeply at turf grass management and physiology.
• A ready source of material is available from which appropriate varieties of common knowledge can be drawn for Distinctness-Uniformity-Stability (DUS) comparisons. These are used by the Centralised Test Centre as comparators in formal growing trials used to describe new varieties for Plant Breeder’s Rights registration.

Field layout and management

Vegetative and seeded varieties of warm-season turf grasses from around the world are established from rooted plugs or sprigs in unreplicated field plots. Each plot measures 3 m x 2.5 m. Plot borders were defined by laying 20 cm x 8 cm sleepers onto the red volcanic soil. The profile within each plot was then built up with 8 cm of greens-grade sand.

The first varieties were planted in May 2000. Because of difficulties in sourcing planting material of some varieties, plots have been established progressively as varieties become available. As well as released cultivars, the collection also includes a number of experimental lines approaching release.

With the 138 available plots fully used by 137 different cultivars or experimental lines and only one duplicate, we have to rationalise entries in our plots, removing some under-performing and non-commercial lines in favour of long-term vegetative germplasm maintenance in large tubs. These are being replaced progressively by new varieties as they are released from quarantine. In general, our aim is to maintain released cultivars in permanent plots, while eventually phasing out experimental lines not developed commercially. Any plots badly contaminated by other grasses that cannot be selectively controlled with herbicides are also removed and replanted to the original variety.

All plots are irrigated and receive the same rate of slow-release fertiliser at regular intervals of two months during the growing season. Species and varieties have been arranged in four mowing groups, for which the height of cut (5, 10, 20 or 40 mm twice weekly through the warmer months) is increased moving from south to north through the experimental site.

Varietal attributes

To date, the growth of each variety has not been formally monitored by regular visual observations. In future, however, we plan to make formal ratings and measurements (e.g. turf quality, colour, seed head production, pest and disease incidence, sod strength) at regular intervals.

Varieties represented

The reference plots currently contain cultivars of 20 different species and 3 types of interspecific hybrids from 13 different genera:

• Axonopus compressus (broadleaf carpetgrass)
• Axonopus fissifolius (formerly A. affinis) (narrowleaf carpetgrass)
• Bothriochloa pertusa (Indian bluegrass)
• Buchloe dactyloides (American buffalograss)
• Cynodon dactylon (green couch)
• Cynodon transvaalensis (Transvaal couch)
• Cynodon hybrid – C. dactylon x C. transvaalensis (hybrid green couch)
• Dactyloctenium australe (sweet smothergrass)
• Digitaria didactyla (blue couch/Swazigrass)
• Eremochloa ophiuroides (centipedegrass)
• Panicum laxum
• Paspalum nicorae (Brunswickgrass)
• Paspalum notatum (bahiagrass)
• Paspalum vaginatum (seashore paspalum)
• Pennisetum clandestinum (kikuyugrass)
• Sporobolus virginicus (marine couch)
• Stenotaphrum secundatum (buffalograss/St Augustinegrass)
• Zoysia hybrids (Z. matrella x Z. japonica and Z. japonica x tenuifolia)
• Zoysia japonica (Japanese lawngrass)
• Zoysia macrantha (dune couch)
• Zoysia matrella (Manilagrass)
• Zoysia tenuifolia (Koreangrass)

This collection is probably the largest of its type in the southern hemisphere.

Funding Support

Between 2009 and 2012, funding was made available by Horticulture Australia (HAL), using the turf industry levy and matched funds from the Australian Government, to pay for maintenance of the turf demonstration plots under project TU09002. The second stage of the project, TU12001, further provides for the improvement and maintenance of the turf demonstration plots. This work will be continued with further HAL funding through until the end of May 2015.

Further information

• Warm season turf grasses
• Order Horticulture Australia report Improvement and maintenance of turfgrass demonstration plots for national research and extension (TU 09002)

Lifestyle horticulture contacts directory

A range of organisations are associated with the lifestyle horticulture industry in Queensland. The following organisations are members of an umbrella group, the Centre for Lifestyle Horticulture (CLH), previously the Australian Centre for Lifestyle Horticulture (ACLH). Through these groups, producers and service providers are able to access a range of services and information relevant to their sector.

Organisations

• The Centre for Lifestyle Horticulture (CLH) aims to unite all segments of the lifestyle horticulture industry. It represents and supports member organisations which include nursery, landscape, turf producers, flower growers, irrigation experts and horticultural professionals. Find out more about CLH.
• Flower Association of Queensland Inc. (FAQI) is the peak representative body for Queensland cut flower and foliage growers. FAQI assists growers with information, marketing, flower promotion, training, industrial relations, representation to government, events research coordination and industry development.
• Irrigation Australia Limited is a national body covering the whole value chain for urban and rural irrigation. It provides information about the irrigation industry and irrigation practices in Australia across a broad range of applications, including those for lifestyle horticulture.
• Landscape Queensland Industries Inc. is an association of professional landscape contractors, designers, suppliers and education providers. It addresses the need for industry standards and education to produce quality landscaping that respects and enhances the environment.
• Nursery & Garden Industry Queensland (NGIQ) is Queensland’s peak body representing production nurseries, garden centres and retail nurseries, and manufacturers and traders in products allied to the nursery industry. NGIQ provides industry representation to government, fosters responsible industry development and provides technical, industrial and commercial services to members.
• Queensland Arboricultural Association Inc. (QAA) is an association for professional arborists. QAA works to preserve, protect, maintain and enhance the environmental, aesthetic and recreational value of trees, and to promote and enhance arboricultural practices and management within the state of Queensland.
• Queensland Council of Garden Clubs Inc. (QCGC) has worked for over 50 years to encourage friendship and cooperation between member garden clubs and to promote the enjoyment of gardening to the wider community. The QCGC website provides information on regional and special-interest member groups, garden shows and special events.
• Queensland Sports Turf Association (STA) is an affiliate of STA Australia. It works to develop professionalism in sports turf management in Queensland by providing resources, ongoing education and networking opportunities. The membership is made up of sports turf workers and allied trades, including those from sports stadiums, golf courses, bowling greens, private schools and councils.
• Turf Queensland is the peak body in Queensland for turf producers and allied industries. Turf Queensland works with government to further the needs of commercial turf producers, fosters responsible industry development and provides member services, information and education. The organisation has been active in conducting irrigation auditing and producer education on water use efficiency.

The project aims to improve the safety and quality of sports fields by a process of defining, measuring and benchmarking the factors which contribute to the performance of a playing surface.

Participating clubs, representing different sports from around Australia, will be provided with an audit report on their playing surfaces and a summary of development options. The information gained will be used to generate a national database, produce a self-assessment tool and determine the need for new products in the turf industry.

Details

Resources

• Roche, MB 2008. Project to BUMP up sports field surface quality. Australian Turfgrass Management 10 (4) 82-83.
• Roche, MB 2008. Modelling for sustainable sportsfields. TurfCraft International. 121 (Jul-Aug.):13.

Fungal diseases of lawns: Predisposing factors

Fungi cause the most serious diseases of turf grasses. Disease problems can be exacerbated by poor turf grass maintenance. Conversely, they can also be improved by the introduction of sound cultural practices. It is therefore important to develop a disease management strategy.

On this page:

• How fungi grow
• Factors that favour disease development
• Identification of disease
• Further information

How fungi grow

Fungi must secure nutrients from dead or living tissues. Some types live only on dead organic matter (saprophytes), but others have the ability to attack living plants (pathogens). These disease-producing organisms also often have the ability to survive and develop on dead organic matter in the soil. When moisture and temperature conditions become favourable, they attack the living tissue of the grass, causing severe injury or plant death.

Most known fungi originate from spores, which usually require warmth and moisture for germination. The result of germination is normally the emergence of mycelium, which is the vegetative part of the fungus. In some types of disease outbreaks, this can even be seen as a fine, cobweb-like substance on the lawn first thing in the morning. Each individual filament of the mycelium is termed a hypha. There is a wide range of variation in the types of spores produced by fungi. This assists in their identification. Many fungi produce both tough resting spores for survival, and also spores for widespread dispersal in wind or water.

Factors that favour disease development

The factors that can favour disease development include high moisture levels, low air movement, thatch accumulation, poor soil condition and nutrition, wear, mowing and the turf variety.

Thatch

Thatch is the layer of dead and living shoots, stems and roots that develops on the surface of a root zone below the green tops. Grass clippings do not significantly contribute to thatch accumulation. A thatch layer of 6-8 mm is beneficial, but, beyond that, problems become more likely – particularly with thatch layers exceeding 20 mm.

Thatch can prevent good air and water movement. Where there is an excess of thatch, the turf tends to produce roots in the organic layer, the condition of which can fluctuate from saturation to drought. Once the thatch is wet, it remains damp for long periods. This favours for the growth of fungi and increases the difficulty of securing good control with fungicides.

Diseases known to be favoured by high thatch levels include: dollar spot, fusarium blights, pythium blight and helminthosporium leaf spot. Dethatching using a metal-tined rake or dethatching machine can assist in controlling these diseases.

Moisture

Adequate, but not excessive, soil moisture levels are important for the health of the grass. Sufficient water must be provided to keep grass growing actively. Too much or too little water can weaken turfgrass and predispose it to disease.

Good drainage must be maintained. Over-watering and excessive periods of waterlogging makes turf susceptible to disease and favours fungal disease development. Compacted areas of soil need to be broken up and treated with gypsum and organic matter to improve soil structure. Core aeration followed by loam topdressing can be helpful over broader areas.

Humid air and heavy dews can also contribute to disease development by keeping the foliage wet.

Soil

An essential requirement for good turf growth is an open, well-drained soil that is not hard and compacted. This need has to be considered prior to planting. Most turf grass species do not grow optimally in heavy clay soils, as roots cannot absorb oxygen properly in prolonged wet periods. In these conditions, the air pockets between small soil particles fill with water and take an excessive time to drain away, suffocating the root system.

Infertile soils, including those with unfavourable pH levels, tend to support only unhealthy and unthrifty plants and are indirectly responsible for disease development. The pH range tolerated varies with the turfgrass species. For example, the pH for green couch is approximately 6.0 to 8.0, however blue couch will tolerate acid soils with a pH of less than 5.5.

Fertilising

Fertilising may affect the frequency and severity of disease attack. Grass that has been weakened by ‘starvation’, or is soft and succulent because of excessive nitrogen fertiliser, is more susceptible to disease attack. Exercise judgment when making applications of nitrogenous fertilisers, particularly in periods of the year when diseases are most likely to occur.

Injury

Excessive traffic may break, tear and wound the plants. Broken or wounded grass blades and stems are more susceptible to wilting and disease attack. Most diseases are favoured by mowing. Mowers wound leaves, disperse infected clippings and spores, and remove leaf tissue that is required for photosynthesis. Keep mower blades sharp, as the damage caused by dull mower blades can be extensive.

Air movement

The circulation of air can reduce disease occurrence. The movement of air as a breeze or wind produces a cooling and drying effect, which is less conducive to turf grass fungi. In a lawn, the regular pruning of adjacent thick shrubs can improve turf grass vigour by increasing light levels and improving air circulation.

Grass selections

Grasses, even cultivars within a species, can vary in their susceptibility to certain diseases. Queensland blue couch (Digitaria didactyla) and seashore paspalum (Paspalum vaginatum) are more likely to be infected with dollar spot (Sclerotinia homeocarpa) than green couch (Cynodon dactylon). Floral smut (caused by Ustilago cynodontis) is found only on Cynodon sp. including green couch, and kikuyu yellows (Verrucalvus flavofaciens) is unique to kikuyu (Pennisetum clandestinum). Spring dead spot (Leptosphaeria spp.) is found on green couch, kikuyu, broadleaf carpetgrass (Axonopus compressus) and soft-leaf buffalograss (Stenotaphrum secundatum). For persistent problems, changing to a more resistant species is worthwhile.

Identification of disease

Because of the different controls required for each individual disease, correct disease identification is essential for effective control. With experience it is sometimes possible to recognise some diseases by the symptoms that are produced on the turf. However, symptoms may vary from place to place and it can be difficult to determine accurately whether a disease is present or whether the turf is affected by other factors. Fungi causing disease cannot be identified with certainty in the field. An accurate diagnosis depends on examination under a microscope and often culturing of the fungus.

Tests are available to identify basic nutritional problems and likely fungal plant pathogens associated with disease symptoms. The cost of an accurate diagnosis is minimal compared to the economic loss from damaged turfgrass and wasted chemical and labour from using an inappropriate treatment method.

If in doubt about a turf grass disease, seek a professional disease diagnosis.

Overview

Further information

• If in doubt, seek a professional disease diagnosis
• Contact us on 13 25 23.

Healthy grass roots in the home garden

Turf grass is one of the most popular choices for outdoor surfacing. Grass is attractive, cool underfoot, stops dust and mud and is readily added or removed from an area should its use change. In addition, it has the benefit of reducing the surface temperature in the surrounding area through its natural evaporative cooling effect, a by-product of transpiration.

In turf, what is seen on top more often than not reflects what is not readily visible – the root system. In grass, roots are specialised plant structures whose main function is to supply anchorage, water, nutrients and some plant hormones to the rest of the plant. In addition, green couch (Cynodon dactylon and its hybrids) and kikuyu (Pennnisetum clandestinum) have specialised underground stems, called rhizomes, which are capable of forming new shoots and roots and contribute what lies beneath the soil. The health and vigour of the root zone is a primary determinant of the quality and vigour of what grows on the surface, which consists of stems, leaves and stolons (above-ground stems capable of forming shoots and roots).

Soil volume

It surprises many people that in unrestricted conditions, grass roots can easily reach a depth of 20 to 30 cm. This is most commonly seen in well-watered sands. However, many domestic garden soils in South East Queensland are clay-based and hard and the turf is shallow rooted. Unfortunately, on some new estates, developers remove the rich surface soil, exposing less desirable and much harder sub-surface soils. A shallow surface layer of topdressing soil may have been applied before laying the turf in rolls. This results in the root zone of the new grass being restricted to the shallow surface layer. These roots find it difficult to maintain adequate water and nutrients for good growth. It is similar to trying to grow grass over rock! Not surprisingly, the shallow rooting depth gives disappointing results for the homeowner.

In areas with shallow soils, rock and recently cleared trees and shrubs, early preparation prior to laying turf is highly desirable. Gypsum can be used to break up the soil, organic manures can be added, and the pH should be corrected. The area should be rotary-hoed and raked level prior to planting. If necessary, additional topsoil should be brought in and added.

In established but poorly performing lawns where soil depth is restricted, the strategies are similar, though the process is slower. To begin with, the lawn should be aerated. This will improve the penetration of water into the profile, carrying with it lighter dressings of gypsum, lime and organic matter. In time, the rooting depth should improve, giving the grass greater resilience.

Compaction

Soil compaction is one of the biggest, but unpublicised, problems in South East Queensland lawns. In heavily trafficked areas, the best option is often to introduce some hard surfacing, creating pathways which subtly direct people away from adjacent areas of grass. In addition to making it difficult for roots to anchor, compaction reduces root zone aeration, while growth above ground is slower.

The root system requires a continuous supply of oxygen for good health. Unlike above-ground growth, roots are incapable of producing their own oxygen. Vital oxygen supplies are normally sourced from pores in the soil and other spaces such as worm holes and decayed root channels. Essentially, in a compacted soil, the root system is unable to breathe properly.

Aeration restores oxygen supplies to the roots. This is commonly done using a drum or belt of 8-10 cm long spikes or corers driven into and withdrawn from the soil at 10-14 cm intervals (hence the term ‘coring’). Light work can be made of this job by hiring a motorised lawn aerator or outsourcing the job to a professional contractor. After aeration, roots are able to spread more freely through the more friable soil profile without the previous physical restriction.

Drainage

In poorly drained soils, water replaces air in the spaces, again depriving the plant of its vital oxygen supply. Where waterlogging is likely, subsurface drainage can be installed. Species that are more tolerant of wet soils can be used, such as broadleaf carpetgrass (Axonopus compressus).

Thatch

Thatch (Figure 1) is the ‘cushioning’ layer of bare stem and other organic matter between the grass leaves and the soil. Some thatch is beneficial, providing mulch, retaining soil moisture and protecting the roots from extremes of heat and cold.

A thick puffy layer of thatch can become a problem by preventing oxygen, water and fertilisers from entering the root zone and creating an environment conducive to disease development.

Thatch is easily removed by routine manual raking or scarification, which encourages healthy new growth. In severe cases, a 5 mm layer of quality loam topdressing may be required.

Water repellent soils

Sand to sandy clay loam soils with a high humus content can develop a problem known as water repellence. If severe, this will prevent moisture from entering the root zone. This results from sand grains becoming coated with organic residues and is exacerbated by dry weather. The problem is readily detected as drops of water stay on (rather than soak into) the soil surface, leaving the soil below dry. If a droplet remains on the soil surface for 10-60 seconds, the soil has moderate water repellence, but above 60 seconds the problem is severe.

The challenge with water repellent soils is to enable them to wet up more readily. For example, incorporating clay into the soil will help to draw moisture into the profile. Proprietary soil wetters, designed for lawns and professional turf use, can also be effective.

Applying sufficient but not excessive amounts of fertiliser is an integral part of good turf management. Periodic testing of the soil has traditionally been used to determine the amounts of different nutrients (other than nitrogen) that should be applied in a fertiliser program, while regular plant tissue testing enables plant nutrient status to be monitored. However, as with any analytical service, the results can only ever be as representative of the area as the sample submitted, and only as accurate as the analytical techniques employed in the laboratory.

Soil testing is an important but sometimes misused tool for turf producers and turf managers. The link below provides access to a paper that explains the principles on which good soil testing is based, how the results should be interpreted and what can be reasonably expected of a soil test in a turf situation. The paper was extracted from the workshop ‘Healthy soils for great turf’, held at Cleveland on 20 February 2006 by the Department of Primary Industries and Fisheries, Queensland.

The subjects considered in the paper include:

• why soil is tested
• taking a representative soil or plant tissue sample
• analytical methods and objective standards for soil and plant tissue testing
• interpreting soil test results and the significance of calibration experiments
• problems with the concept of the Base Saturation Ratio approach
• the complementary use of plant tissue analysis.

What is a healthy soil?

Author/s:
Tony Pattison

Publication details:
Department of Primary Industries and Fisheries, South Johnstone Research Station

Published:
February 2006

Article summary:

Healthy soils have physical, chemical and biological properties that promote sustainable production. For the production of turf, the soil must support profitable plant growth without impacting on the surrounding environment and without degrading the soil resource.

The article ‘What is a healthy soil?’ defines soil health and looks at symptoms manifested in unhealthy soils.

Readers are encouraged to take a holistic view of how a soil environment is created and to monitor key physical, chemical, biological and production indicators.

The article is extracted from the proceedings of the workshop ‘Healthy soils for great turf’, held at Cleveland on 20 February 2006 by the Department of Primary Industries and Fisheries, Queensland.

History

The land that would become Redlands Research Station was originally cleared during the 1880s. The government purchased the first 8.5ha in November 1948 to develop a research farm, with further purchases made in 1953 (43.5 ha) and 1958 (14.4 ha).

The station now has a total area of 66.4 ha. Over half the land is uncleared and provides valuable habitat for a range of native wildlife species.

Location and geology

Redlands Research Station is situated at Cleveland, near the shores of Moreton Bay about 30 kilometres from Brisbane, Queensland. Being close to Moreton Bay, elevation is low and ranges from 15 m above sea level on the flats of Hilliards Creek to 37 meters above sea level on the higher areas.

Climate

The climate at Redlands Research Station is generally temperate with a widely dispersed but summer dominant rainfall pattern. Of the annual average rainfall of 1322 mm, two-thirds usually falls between November to April.

Temperatures are mild, with maximum temperatures rarely exceeding 32^oC and minimums rarely dropping below 5^oC. Terrestrial minimum temperatures of -2 or -3^oC are recorded once or twice a year.

Soil types

The soils of Redlands Research Station can be broken into three major groups:

• east of Hilliards Creek, soils are typical krasnozems – coloured brown to dark brown, of clay loam to light-medium clay texture and moderately deep with adequate internal drainage
• west of Hilliards Creek, soils are variable yellow podzolics with a shallow ‘A’ horizon varying in colour from grey to brown, overlying a mottled clay ‘B’ horizon. These soils erode easily and have poor internal drainage
• along the creek flats of Hilliards Creek is an area of silty soloths. These soils are shallow with poor internal drainage.

Irrigation

Trials conducted on the station are assured of access to water. Water is drawn from Hilliards Creek, fed by greywater from Redland City Council. The station also has access to a greywater pipeline owned by the council. Overhead, pop-up and trickle irrigation systems are in use.

Facilities

• Industry services building, home to a number of industry groups and the main administration building
• Science services building, which houses research staff
• Queensland crop development facility, comprising propagation facilities and five glasshouses, three of which are designed for PC2 level plant quarantine
• Research and development nursery complex, with state-of-the-art tunnel house and extensive shade houses
• Large shade houses
• Plastic tunnels for sheltered growth environments
• Fruit fly-proof growing areas
• Machinery sheds
• Engineering workshops
• Turf research laboratory
• World-class tissue culture laboratory and growth rooms
• Greens testing facility
• A living turfgrass library of over 130 demonstration plots of warm season turfgrasses

Further information

• DEEDI Customer Service Centre

With water restrictions the norm in South East Queensland, there are concerns that grassed areas will be replaced by dust.

Aside from the impact on aesthetics, cleanliness and the health of people with respiratory problems and allergies, a poor lawn can drop the overall value of your property by 5 to 10%. Unless you are completely prohibited under the by-laws of your local council from watering lawn and there is no natural rainfall, the following simple measures will enable you to sustain your lawn.

Before planting

The development of a strong, healthy root system is encouraged when grass sod or seed has been established on a thick layer of friable topsoil. The deeper this layer, the greater the opportunity for turfgrass to establish deep, drought-tolerant root systems. In areas were the topsoil is shallow, this may require a combination of rotary hoeing and topdressing with a sandy loam prior to planting.

Water penetration

During times of drought, it is essential to aerate. If your lawn has not been aerated within the last 12 months, make this a priority. Many grassed surfaces have become compacted through trafficking and past deluges of rainfall, forming a surface hard pan. These surfaces prevent applied water from entering and becoming successfully stored within the soil.

Compaction layers can be broken up using a soil aerator. You can get a contractor to do this work, or hire equipment and do it yourself. The aeration equipment will spike the lawn, opening up a channel for water and oxygen.

As the surface of a soil dries out, it is not uncommon, particularly with sandy soils, to encounter the problem of water repellency. To test for this, fill an eye dropper and dispense a single droplet onto a dry exposed soil area. If this droplet does not soak into the ground within about five seconds you may have a problem. The longer it takes for the droplet to soak in, the more severe the problem. In some cases, droplets are still intact after 10 minutes.

Repellency is caused by the upper-most soil layer and the granules in it becoming coated with organic compounds from decomposing organic material. Sand is more prone to water repellency than clays. When water is applied, the soil dispenses it sideways, causing localised dry spots, a problem which is more pronounced in times of water scarcity. Soil rewetting agents can partially solve this problem. Products and professional advice regarding the range of soil rewetting agents on the market may be obtained from your local nursery.

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Microclimates

When considering how available water might be usefully applied to lawns, critically examine the micro-environments that exist in your yard. Shaded areas and areas receiving run-off from any incident rainfall near the roof-line or paths and driveways will not require as much water as high-sunlight exposed areas. Water use can be reduced in these areas.

Performance expectations

During drought you cannot expect to have a lush, green, European-style lawn. The objective for lawns under drought conditions should be to maintain sufficient living top growth and root systems to hold soil in place. Under these conditions you need to accept that some varieties of grass will shut down and become straw-coloured or start to purple. When the rain does arrive, however, it is then a quick path to re-greening and improved vigour.

It can be tempting to re-design gardens to replace turf with gravel or paving. The consequence of this however is reduced flexibility in how this open space may be used, the additional build-up of reflected summer heat, and absence of all the attributes associated with having a living lawn.

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Turf species and varieties

Under Queensland conditions, both green and blue couch have demonstrated drought tolerance over a sustained period. There are a number of varieties of green couch (Cynodon dactylon) and blue couch (Digitaria didactyla) on the market. Of the green couches, the older varieties, Wintergreen and Greenlees Park, are still widely used, despite the introduction of a number of more specialised new releases. Blue couch is widely naturalised over much of Queensland and is sold as common Queensland blue, Aussiblue and Tropika.

Under dry conditions, the couches wilt and then tend to become straw-like. Their root systems are robust and generally survive to produce a rapid greening response as soon as water becomes available.

Sales of newer species like the buffalo grasses (Stenotaphrum secundatum), zoysia grass (such as Zoysia japonica) and seashore paspalum (Paspalum vaginatum) are increasing. Independent research is underway at the Queensland Primary Industries and Fisheries to study the drought tolerance of the buffalo grasses.

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Watering

Your times of access to water and when and how it is applied is subject to local council by-laws. Check with your local council for details. Within these constraints: less frequent but thorough watering will encourage greater root depth.

Infiltration is improved if the lawn is wetted, the water allowed to soak in for a short period and then the surface is watered again. This will allow the moisture to penetrate deeper into the soil, encouraging deeper roots, which are able to access more available soil moisture. Frequent light watering encourages shallow roots, and the plant will quickly require more water.

Water at night as the evaporation levels are far lower than during daylight hours. Use a sprinkler rose with a cut-off mechanism on the end of your hose when hand watering to obtain an even distribution of water that falls gently onto the grass. If bucket-watering, use a watering can.

As overall lawn growth is reduced during times of restricted watering, fertiliser use should also be temporarily minimised.

Mowing

Each pass of the mower blade over a lawn produces a level of stress on the turf. Under moist conditions this is of little consequence as the grass is growing rapidly and is capable of a quick recovery. In droughted lawns new leaf blades do not readily regenerate. Reduce the frequency of mowing and increase the mowing height to retain more individual leaf blades as the lawn starts to thin out. Do not remove more than the top third of leaf growth at a single mowing.

It is also important to keep the mower cutting blade sharp. This will help to avoid feathering or tearing of the leaf blades and the subsequent die-back.

The best type of mower to use during a dry period is a mulching mower. This will return the clippings onto exposed soil surfaces and assist in the retention of any available moisture. Mulching will be most effective when some leaf blades are being recycled into the lawn, rather than just seed heads.

Usage

During times of stress, where possible try to minimise traffic on the grassed area. Trampled leaves and stems do not readily recover in times of restricted growth.

Herbicides

Avoid applying herbicides for weed control on droughted lawns. Although the herbicides may be registered for use on your lawn type, they may cause additional subtle stresses on your grass and exacerbate existing problems with lawn vigour during dry times.

Tips for managing turf in dry times

• prepare the soil surface to encourage the formation of deep grass roots
• aerate
• treat water repellent soils
• water thoroughly and at night to reduce evaporation.
• split your watering times to reduce runoff.
• water according to the needs of different areas.
• accept a lower standard of lawn surface.
• use a mulching mower.
• reduce mowing frequency and increase the mowing height.
• minimise traffic.
• do not apply herbicides.