By Phil Sharples
Understanding the basic principles of turf management are important. Listed below are six basic practices that help promote, establish and sustain sports turf.
What is aeration?
Aeration is the process of cultivating the soil beneath the grassed surface without disrupting the turf's surface characteristics. Most soils will need aeration if they receive wear from traffic, be it human or mechanical.
Traffic on a turf surface compresses the soil beneath. This compression or compaction of the soil particles reduces the pore spaces between them. Compaction reduces the amounts of available oxygen that is held within the pore structure that is so vital for root growth, water movement and general plant health.
Any decrease in the size and number of soil pores will lead to many detrimental effects on the grass surface above. Drainage rates will be reduced and the rate at which water enters (infiltrates) the soil will also decrease, meaning a wet, soggy, un-usable surface for long periods after rain or through the winter period. Heavy compaction actually prevents the grass plant rooting as the pore spaces in the soil are too small to allow any roots to penetrate.
Compaction leads to many problems including:
Increased amounts lateral surface rooting leading to increased amounts of thatch
Poor summer colour is exhibited by the grass leaves
Poor drought resistance of the plant
Poor wear tolerance of the plant
Ineffective use of water and fertilisers
Can lead to an increase in moss
If carried out correctly aeration will increase the levels of oxygen in the soil so vital to healthy root growth.
Aeration increases the soils ability to absorb water, preventing flooding and making the best use of any water applied.
Aeration will help breakdown the thatch layer while also ensuring that any fertiliser applied can gain access to the soil.
Aeration allows the incorporation of top-dressing to key into the soil surface but, perhaps the most beneficial effect of aeration is that when carried out correctly the operation is environmentally friendly, has no detrimental effect on your lawn and the benefits the entire lawn surface.
When is this done?
Aeration can essentially be carried out at any time of the year. Aeration should not be carried out when the soil is in a wet, saturated condition. Aeration of a wet soil leads to smearing when the tines are pushed in and pulled out. Smearing seals the soil preventing any air and/or water movement. Essentially this will cancel out all the benefits aeration brings.
All plants require lots and lots of water. The grasses on any sports turf surface are no different. The grass plant needs water as it forms over 80% of its entire make-up; only 15% of the grass plant is actually dry matter.
Water is an essential component of photosynthesis and without it the grass cannot make food for growth and development. It is used to transport nutrients around the plant. The water inside the plant cells actually makes it stand upright (acts like our skeleton) and without this water the plant will wilt and eventually die. Over 90% of the water taken up by the plant is lost back to the atmosphere. Most water taken up is only used to cool the plant before being released back into the atmosphere.
It is therefore essential to keep up the soils reserves in order to maintain a dense, uniform and aesthetically pleasing lawn. If the plant is to produce a deep and extensive root system the soil must have water in it as this acts as a stimulus for root growth. With correct watering practices the grass plant will develop a deep and extensive root system that eventually leads to it being very drought resistant, allowing the plant to recover rapidly from wear and maintain good colour throughout the year.
How is the water lost?
Water in the soil is lost in two ways: Firstly, after water has entered the plant through the root system it travels upward to the plant leaves and is eventually lost to the atmosphere through thousands of tiny opening on the leaves called stomata. This action of water loss is termed transpiration. Secondly, water is lost from any exposed soil surface between the grass plants. This is termed evaporation. Together (Evapotranspiration) these processes account for the majority of the water lost from the soil.
A deficiency of water in the soil leads to a situation where water loss from the plant through transpiration exceeds what can be taken up by the roots; this causes stress to the grass plant. If this stress persists for more than a few days wilting may occur, the grass will dry out and brown patches may develop on the lawn.
How should I apply water?
The obvious thing to say here is "water when the soil is in a dry state". Though, it is advised to water turf heavily and infrequently. Generally the lighter the soil (the more sandy) the more water will need to be applied. The heavier the soil (Clayey) the less water will need to be applied.
Heavy application of water once every one - two weeks (depending upon weather) during the growing season with perhaps further lighter applications every 3 - 5 days in-between will encourage your grasses to maintain good top-growth, density and colour. Keep a check on the weather as you do not want to be over-watering the turf surface, not only does this waste water but it can also encourage the plant to produce shallow roots (the roots do not have to work to access water as it is always available on the surface!)
The benefits of correct irrigation:
You will help the turf surface become drought resistant.
The grasses will retain better colour throughout the year.
The turf area will recover from wear at a much faster rate.
The turfgrasses will become more resistant to attack from pests and diseases.
A healthy, thick turf discourages the growth of many problem weeds.
Vertical mowing (Scarification)
What is vertical mowing?
The pedestrian machine used for this operation is around the size of a standard lawn mower. Scarification can be carried out any time of the year as long as the grass is growing strongly enough to recover.
The main purpose of scarification is to remove an organic material that occurs naturally just below the turf grass leaves, but above the soil layer. Scarification removes thatch and moss, allows the soil to exchange gases and helps promote a thick, lush grass surface.
What is thatch?
Thatch is an organic layer consisting of dead, dying and living stems, roots and leaves, in fact, all parts of the grass plant. A thick thatch layer will have a number of detrimental effects on any lawn. The surface will feel spongy and can stay wet for longer. It prevents the infiltration of water and therefore affects the drainage properties of the lawn.
Thatch also acts as a harbour for pests and diseases to develop and feed in. It promotes the ideal conditions for weed invasion, mosses and undesirable grass species. Thatch can also trap within it any nutrients applied to a lawn resulting in a very shallow root system. Shallow rooted grasses offers poor drought resistance, colour and density and the plants ability to recover from wear will be drastically reduced.
Scarification should be carried out for a number of reasons
Reduces the amount of moss in the turf surface
Increases the density of some grasses
Removes undesirable thatch layers
Allows water and nutrients and oxygen access to the soil layers resulting in a healthier more drought resistant turf surface
Improves water drainage rates
Creates the correct conditions needed for the germination of newly sown seed
Reduces water run-off from the turf surface
Prevents the formation of algae
What is top dressing ?
Top dressing is a process of applying additional soil/sand materials to improve the soil profile particularly at the playing surface interface of the grass plant and rootzone profile. The benefits of top dressing are many:-
Restores surface levels
Improves moisture holding capacity
Dilutes organic matter/thatch
Improves surface drainage
Sand dressings improve porosity of the rootzone by increasing the amount of air filled pore spaces.
Protects the crown of the grass plant
How should it be applied?
It is important to apply the top dressing when both the material and the grass surface are dry, as this will ensure a rapid incorporation of the material around the base of the plant and into the rootzone profile. Care should be taken on the amount of dressing used. If you apply to much dressing you are likely to smother the grass plant, which may slow plant growth or, in the worst cases, kill the plant.
The top dressing should be correctly incorporated into the existing rootzone otherwise rootbreaks and layering can occur, having a resultant detrimental effect on the playing quality of the turf. To prevent the formation of rootbreaks and layering when top dressing it is important to carry out some additional cultural practices to help integrate the new material into the soil profile. This is achieved when you carry out scarifying and aeration works prior to application of top dressings.
The amount of material required will be dependant on the type of playing surface you are top dressing. Fine turf facilities such as golf, bowls and croquet will require light frequent dressings. Most Greenkeepers tend to top dress little and often, usually on a monthly basis applying in the region of 0.5 tonnes of material to a 500m2 area during the growing season.
However, the amount of top dressing for football pitches will differ. Ideally between 60-100 tones of material should be spread over the whole pitch (6000m2).
Once the top dressing has been applied it is important to brush/drag mat the material into the playing surface.
What is a fertiliser?
A fertiliser provides one or more essential plant nutrients to aid growth and health and can be applied to the turf surface or rootzone. The main fertiliser nutrients applied to turf are Nitrogen, Phosphorus and Potassium, NPK followed by Iron and occasionally Magnesium.
Why apply fertilisers?
The benefits of using fertilisers are many:-
Increases sward density
Aids the plant's recovery rate
Improves root biomass
Improves the plant's ability to resist disease attack
Improves colour and verdure of the sward
Maintains plant health
The effects of fertilisers
There are many different formulations of fertiliser. In the main they are applied in either a granular or liquid state.
To determine which one is most appropriate you will need to assess your plant's needs.
In deciding which fertilisers to use, it is important to consider the types of grasses which are to be encouraged for the area in question as well as the existing ground conditions, e.g. soil pH, soil texture and available nutrients. You can help confirm the nutrient status of your soil by carrying out a soil nutrient test. This requires you to send a number of soil samples to a soil Lab. There are many commercial laboratories that will test your soil and give you a report recommending your needs.
Once you receive this information you will be better placed to identify a fertiliser product to suit your needs. In the main most groundsmen usually apply an application of spring, summer and autumn fertilisers to maintain optimum grass growth.
What is over seeding?
Over seeding is the process of applying new seed to an already existing stand of grass. It can be carried out on small worn areas or across the whole lawned surface. Over sowing is an ideal way to produce a thick healthy lawn that looks good the whole year through.
Over sowing is also carried out to replace the annual grass species found in many sports surfaces that simply die off each year. All grasses naturally produce and lay seed when they flower each year (through production of a seed head), but, if a sports turf surface is mown, then the grass is prevented from producing this due to the low height of cut forced upon it by the mower.
Why over seed?
Over seeding is carried out for the following reasons:
A thick and dense sward is required
To allow the sowing of desirable grass seed such as species that are drought resistant, especially wear resistant, shade tolerant or simply retain a better winter colour
Where the present standard of turf grass species is so poor that routine maintenance cannot improve it
When should I over seed?
Over sowing of new grass seed should be carried out from Spring until Autumn time. Any seed sown during the warmer summer months will need to be thoroughly watered throughout any prolonged hot, dry periods. The best time to over sow is the Autumn as at this time of year the soil is warm and the amount of natural rainfall is increased. Sowing in the Autumn will also allow the plant to develop an extensive root system through the winter period.
Over seeding is best carried out after scarification, as this maintenance procedure allows the seed to integrate into the sward and aid the germination process.
Allows suitable grass species to adapt to your turf surface
Increases the density and improves the lawn's texture
Ensures that the lawn stays healthy throughout the year and maintains good colour
With increased density a turf surface will actually suppress the growth of weeds
Sowing drought resistant grasses can decrease the amount of water that needs to be applied to the turf surface