Spring renovation on natural turf facilities
By Laurence Gale
This month's feature article is on the spring renovation of natural turf playing surfaces. With the onset of the new grass growing season, it is imperative that Greenkeepers and Groundmen implement a renovation programme to prepare and refurbish their playing surfaces. Spring renovation involves a series of operations and inputs that are initiated in sequence and complement one another. The success of spring renovation is dependant on a number of factors:-
- The type of facility - golf, bowls, football, rugby, tennis etc.
- The playing standards of the facility - school, Local Authority, club, County or International standards).
- The current state of the sward and soil profile will determine and prioritise the extent and nature of the renovation works required.
- Groundsman / Greenkeeper's knowledge and experience.
- Resources available - machinery, staff.
- Water resources.
- Availability of materials and products.
- Availability of specialist services - contractors, consultants.
- Planning and time - the window of opportunity.
- Costs / Budgets.
All of the above factors will play a part in determining the level and quality of spring renovation.
The following activities are generally implemented during spring renovation and usually carried out in the following order:-
- Mowing the sward, preparing surfaces for renovation.
- Moss treatment.
- Scarification, removal of unwanted debris.
- Aeration, decompaction of soil, improving air and gas exchange in soil.
- Top dressing, restores levels and improves surface drainage.
- Overseeding, restores grass populations.
- Fertilising, provides nutrients for grass growth.
- Brushing to incorporate dressings and to help the grass stand back up.
- Watering / Irrigation.
Weed control may be dealt with prior to or after spring renovation. Any accumulated moss growth should be dealt with by applying an approved moss killing chemical, wait for it to die, then remove by scarification.
To maximise the affect of spring renovation it is essential to evaluate the existing condition of the turf. This can be done by carrying out a series of soil tests to measure soil pH, organic matter content, particle size distribution (PSD), bulk density and soil penetration resistance. Coupled with a visual assessment of how much grass cover and weeds are in the sward, this will help determine the level and extent the spring renovation should take.
A turfgrass sward may decline through a number of reasons - lack of cultural practices, drought, weeds, diseases, shade, poor soil, neglect, abuse and over use. All natural sports turf pitches and facilities will encounter wear from play and the effects of compaction. Even on well constructed pitches and greens the re-arrangement of soil particles and accumulation of organic matter can all influence the physical performance of the surface layer in terms of it's drainage and playing qualities. Spring renovation helps restore turf health and quality, rejuvenating the soil and sward after winter, thus preparing the surface for the new growing season.
The grass is usually mowed prior to starting any renovation works. The objectives of mowing is to clean and prepare the grass surface. Grass growth in spring can be uneven and varied. Mowing the grass to a uniform height will help prepare an even surface for scarification and topdressing operations.
Cuttings should be boxed off, and the height of cut will depend on the type of surface you are preparing. For fine turf, golf greens and bowling greens the cut may be down to 5-6mm, for tennis and cricket outfields 8-12mm, and for football 25-30mm.
Cylinder or rotary mowers can be used as long as they are able to collect the cuttings.
During growth the grass plant produces a lot of dead material above and below ground level.
Above ground (Thatch layer): dead and decaying leaf and root material develops and accumulates to form a thatch layer of matted material. This layer of thatch can create a microclimate that is detrimental to turf, preventing water infiltration and providing ideal conditions for fungal and disease establishment.
Below ground (Mat layer): root growth involves increased biomass of the root system and, like the grass shoots above the ground, some of this new matter dies back leaving a dead mass of root material which can often prevent and restrict new root growth and affect gaseous exchange in the soil. It is important to remove this debris.
Scarifying is the term used to remove this unwanted vegetation. There are many different ways and methods of scarifying lawns and turf surfaces. The process usually involves a raking / cutting action to clean out the thatch debris, and can be done manually using spring tine rakes or mechanically using specially designed rotorakes, verticutters and knife action machines.
The choice of method and type of machinery used will be dependant on:-
Size of the area to be scarified.
Location and aspect of site.
Type of surface - fine turf or outfield turf.
Depth of operation.
The amount of debris to be removed.
Retention of organic matter.
It is important to validate what you are trying to achieve and what will be the consequences if you over do it. Trying to remove too much debris is likely to scar and damage the playing surface, resulting in surface disfigurement that may affect ball role and play.
There are many different types of machines designed and available for scarifying turf, all offering different cutting depths, with different power and speed variations, with and without collection boxes. Machines can come in many shapes and sizes, some are pedestrian, some tractor/ prime mover mounted.
The depth of penetration for effective scarifying must be through the mat layer and into the soil. For an effective, vigorous scarifying, the blade should be at least 3 mm wide. Scarifying in two directions, at an angle of less than 90 degrees, gives the most vigorous working. Scarifying at right angles has the tendency to cause severe damage, with the small squares of turf being ripped from the surface. To restore the playing surface after vigorous scarifying will require an application of top dressing materials to restore levels and provide a seed bed for grass seed.
In general, the level and quality of scarification is dependant on the type of machinery available. Not all groundstaff have their own machines and, if they do, may have a particular type that can only achieve a certain level of working depth and performance. Hiring can be beset with problems. The machines may not be available when you want them, so it is important to check availability and book early when hiring. Hired machines can often be unreliable, often breaking down or having worn blades. The advantages of purchasing your own machine enables you do buy exactly what you need to do the job you want.
The choice of machine is critical. It is no good spending money on a machine that does not or cannot remove the quantity of debris desired or achieve the depth of penetration required. It is best to seek advice and ask for demonstrations of different manufacturers' machines. This will enable you to find one that meets both your facility needs and budget.
Below are a few example of the types of scarification equipment available:
|Verticutting units for de-thatching||Ride on mowers with verticutting units for de- thatching.|
|Fine turf scarifier, removes and controls thatch on all fine turf areas.||Heavy duty powered scarifier, de-thatcher and linear aerator.|
|All surface scarifier for vigorous renovation.||Combined de-thatcher and linear aerator with collection for larger areas.|
Aeration is an important part of the renovation programme. Not only does aeration remedy any compaction problems by restoring and improving air movement in the soil profile, it also provides channels and openings for the top dressing materials to integrate, particularly if hollow coring or hollow tines have been used. The benefits of aeration are:
- Improves soil surface drainage (water infiltration).
- Helps to increase soil temperatures.
- Increases soil pore space.
- Allows gaseous exchanges in the soil (oxygen, carbon dioxide) that improves root depth (growth and development).
- Aids integration of top dressings into soil profile.
- Aids the breakdown of thatch /organic matter.
- An aid to promoting better surface levels that will increase ball roll /speed.
- Aids surface firmness / dryness thus increasing ball bounce and surface grip.
- Using solid tines (hand forks, pedestrian and tractor mounted).
- using hollow / coring tines that remove soil cores from the soil.
- Using flat / star tines.
- Disc / blade implements (linear aerators).
- Compressed air and water systems.
The table below depicts some of the aeration machinery used on different types of surfaces. There are many more makes and types of equipment available, including hand held tines, forks, pedestrian aerators and large tractor mounted aerators.
Bowling greens / Croquet / Golf greens
Coring machine Sarrel rollers
Golf greens / Tees
Solid tine Compact Vertidrain Verticore machine
Football / Rugby / Golf fairways /Horse racing and polo fields
Vertidrain Linear Aerator
The application of a good quality top dressing, in combination with a suitable aeration programmes, will go a long way to counter the ravages of play. In addition, on sites where the original soil is not necessarily suited for sporting activity, the use of appropriate topdressing materials can contribute significantly to the production of an acceptable playing surface by making progressive changes in the composition of the surface layer. Sand companies and top dressing suppliers are offering a wide range of materials for use on sports areas.
Benefits of top dressing:-
- Restores surface levels.
- Stimulates new root and shoot growth.
- To cover seed (soil seed contact to initiate germination).
- Increases water holding capacity of the soil.
- Improves soil structure.
- Increases nutrient retention.
- Improves surface drainage.
- Increases air filled porosity (air pores in the soil).
- Increases ball bounce/ ball roll.
Choice of top dressing materials will be determined by a number of factors:-
- Existing soil type.
- Type of facility construction - USGA specified greens, specialist sand constructed sports fields.
- Different sand types - to improve surface drainage.
- Organic Materials - composts.
It is important to evaluate the existing soil/sand composition of your facility. This can be achieved by sending soil/sand samples away for testing. Using the wrong dressing material, or creating a layering effect, can cause severe drainage and rootbreak problems. To help choose the correct top dressing material, it is often best to seek advice from top dressing suppliers or qualified consultants or agronomists.
There is a wide range of materials available for top dressing, ranging from straight sands, clays, loams and local soils materials through to purpose mixed rootzones combining clays, loams and sands. These mixes can be tailored to suit the customers needs, and can range from 80/20, 70/30 and 60/40 sand/soil percentage mixes.
The success of top dressing will also be influenced by the amount applied and how well it has been worked into the turf surface. Applying too much dressing will have a detrimental affect, smothering out the turf and increasing the likelihood of disease, slow grass growth and, in some cases, will kill the turf.
The amount of top dressing required will depend on the depth of material used x the surface area of the site. Most Greenkeepers in the spring may only be applying about 1-2mm of dressing per green (average size 500m2), about 0.75-1.5 tonnes of top dressing per green, whereas in the autumn renovation programme more than 2 tonnes per green may be applied.
Similar amounts of dressings may be applied to tees and approaches. When adding up the total amount of dressing required for a 18 hole golf course you suddenly see yourself having to cater for well over 80 tonnes of material - a long winded job if done by hand! On average, for top dressing football pitches, about 60-100 tonnes of material per pitch are required.
There is a range of machinery that can transport and spread top dressings accurately:
|Spinner for light regular top dressings.||Precision brush top spreader.|
|Brush and spinner top dresser.||Pedestrian spreader.|
To re-establish grass cover on the playing surface, it is necessary to overseed the area with new grass seed. It is important to choose appropriate seed mixtures for the given sports surface. There are many varieties of grass seed available, bred to perform for particular sports and soil types.
It is not cost effective to use cheap or old grass seed stock, as germination and establishment is likely to be poor. Buy your seed from a reputable company which specialises in developing and marketing quality grass seed mixtures. These seed varieties may be more expensive but they do guarantee quality and performance.
Overseeding rates will depend on a number of factors:
- Type of seed.
- Condition of existing turf (how bare).
- Type of seed spreader/drill machine used.
- The number of passes (sowing the seed in different directions).
Most seed suppliers will recommend sowing rates but, as a rule of thumb, it will generally be about 35grams of seed per sq/m. Temperatures above 12°C, a moist, well-aerated seedbed, close seed/soil contact are primary requirements for rapid grass seed development. Machinery designed to sow grass seed include disc, direct drilling, oscillating and broadcasting mechanisms. The best results are achieved when the seed has direct contact with the soil, and preferably below the soil surface. Seed that is left lying on the surface and not in direct contact with soil is prone to drying out and being eaten by birds. Ensure moisture is available for germination.
|The Proseeder performs four tasks during seeding, making holes, injecting seed, covering with top dressing and brushing materials into the surface.||15 disc Overseeder for seeding large areas, capable of overseeding six football pitches in a day.|
Selection of grass seed is important. There are many varieties of seed now commercially available, offering many different performance characteristics and growing habits. New varieties have been introduced for specific requirements, sport related dwarf rye grasses for cricket and tennis, bents and fescue grasses for fine turf golf and bowling greens, and shade tolerant grasses for stadia use.
It is vitally important to buy your seed from an approved seed company that can verify the quality and performance of its seed mixtures, with relevant certification and documentation. This prevents you buying seed and finding out it has been contaminated with weed seed or inappropriate grass varieties which, in turn, affects the quality and performance of your sward.;
Prior to applying any fertilisers it is essential to obtain the nutrient and pH status of the soil. This can be achieved by sending soil samples to a soil laboratory which will carry out a nutrient analysis of the sample. Once obtained you will be able to choose a product that offers you the correct N P K fertiliser ratio for your soil.
Many of the leading fertiliser manufacturers offer a balanced spring or re-seeding fertilisers for turf renovation. The benefits of applying N P K fertilisers are:
- Stimulates seed growth.
- Increases tillering and shoot growth.
- Increases root growth.
- Balances grass growth.
- Increases grass plants vigour and resistance to disease.
- Improves grass colour.
These fertilisers can be supplied in granular or liquid form. Granular products tend to be more widely used because they are easier to handle and distribute. Over dosing or applying granular fertilisers without enough soil moisture being present may result in the grass becoming scorched, resulting in scarring or death of the grass plant. Fertiliser application is only effective if you ensure uniform coverage. Granular fertilisers can be applied with either a drop (gravity) spreader or a rotary (centrifugal) spreader.
|Tractor mounted spreader||Pedestrian rotary spreaders|
Brushing / Dragmatting / Luting:
Once all top dressings, grass seed and fertiliser materials have been incorporated into/onto the surface, it is important to work the material into the profile by brushing, dragmatting or luting. These operations ensure the materials are worked in evenly, and prevent any excess material remaining on the top. This operation is best done when the surface is dry, enabling the material to distribute itself easily.
|Dragbrush||Tractor drawn brush|
Irrigation / watering:
To renovate successfully, adequate water must be available from seeding through to completion of germination. Try not to allow newly overseeded areas to dry out once watering has commenced. Initially, maintain a constantly moist seedbed with frequent waterings of short duration. As newly germinated seedlings begin growth, decrease the frequency, and increase the duration of watering to encourage deeper rooting.
Spring renovation is often a time consuming and expensive exercise. Successful renovation requires detailed planning and programming, to ensure the right materials and equipment are available and working throughout the renovation process. Generally, most renovation programmes have to be completed in a short period, between 1 and 4 weeks, usually during the month of April.
However, when successfully implemented, the results of the spring renovation should promote and produce a healthy turf sward capable of withstanding the onslaught of the playing season ahead.