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Turf
 
                   
 
Preparing the soil
Drainage
Soil pH
Levelling the site
Firming and raking
Watering
Fertiliser
Establishing the lawn
Turfing
Sowing seed
Vegetative propagation
Acknowledge-ments
 
 
 
 
Laying down a new lawn

Preparing the soil

Eradicating weeds

Killing the existing turf is necessary to eliminate unfavourable lawn grasses and perennial weeds, particularly weeds that have rhizomes or deep tap roots, as they regenerate rapidly from small pieces of root. Examples are dandelion (Taraxacum officinale), nut grass (Cyperus rotundus), docks (Rumex spp.), soursob (Oxalis pes-caprae) and other Oxalis spp.

Initially, apply a broad-spectrum non-residue herbicide such as glyphosate or essential oils in ‘Organic Interceptor’ to eliminate grass weeds and some broad leaf annual weeds. Weeds that survived the first herbicide application should then be eliminated using a selective herbicide (see section on weed control).

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Drainage

Drainage is usually only required on heavy clay soils, and can be improved by incorporating two parts sand to one part of soil. A drainage system of pipes laid in a trench, which is backfilled with gravel, is a more effective alternative. For most loam soils that receive 600-1000 mm rainfall, one drain every 5-8 m is recommended. Heavier clay soils or sites in areas with rainfall above 1000 mm will require drains that are laid at closer intervals.

Soil pH

Grasses grow satisfactorily at pH levels of 5.5-7.0. In this pH range, nutrients that the turf grasses need are soluble, rather than being bound up in the soil. Soil pH can be tested for using a kit available from garden centres. For acidic soils (pH less than 5), dig or rotavate lime (calcium carbonate) into the soil, the recommended rate depending on the starting pH and soil type (Table 1).

Table 1: The amount of lime (g/m²) required for different soils.

Starting pH Sandy Loam Clay
4.5 190 285 400
5.0 155 235 330
5.5 130 190 260


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Levelling the site

After levelling the site by eye, more accurate levelling can be achieved by running builder’s string on pegs that have been inserted into the ground.

Firming and raking

Tread the soil evenly about three times all over to firm it. Rake the surface to provide a fine tilth. Remove stones greater than 1 cm diameter if the soil is being prepared for sowing, or 2.5 cm diameter for turfing. Allow 3-4 weeks for weed seeds to germinate, and treat the area with glyphosate to kill them.

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Watering

New turf requires watering at frequent intervals to keep the seed or turf moist during this initial two-week growth period until the root systems have developed. Treat the lawn as an established turf after one month.

Fertiliser

A few days before establishing the lawn, apply a compound granular fertiliser containing nitrogen (N), phosphate (P) and potassium (K) to the prepared soil surface at a rate of 150-200 g/m². Rake the fertiliser into the surface.

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Establishing the lawn

Turfing

Turf can be applied any time of the year except during hot dry periods. Lay turf on to moistened soil surface to encourage root development of the turfgrass. Starting at the edge of the site, lay the first row of turf in a straight line. Standing on planks placed on the first row, rake over the soil on which the next row is to be laid. Lay the second row so that the turves form an alternate bond, like bricks in a wall. Cut the edges to shape with a sharp flat or half-moon spade; to the inside of a hose for a curved edge, and against a plank for a straight edge. Roll the newly laid turf with a light roller (50 kg), and brush a top-dressing of sand and soil mix into the joins between the turf pieces to encourage the roots to spreads into the gaps. Water the turf thoroughly.

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Sowing seed

Calculate the amount of seed required by multiplying the size of the area (m²) by the recommended sowing rate (g seed/m²). Shake the seed bag to mix the seeds.

If sowing by hand, divide the area into equal sized sections, e.g. 1 m x 1 m, to ensure an even distribution of seed cover. Measure the correct amount of seed (Table 2) for each section, and scatter half the amount in one direction and the remainder at right angles. Repeat for each section.

If sowing by machine seed spreader, divide the amount required for the lawn by half, and sow one half in one direction and the remainder at right angles to the direction of the first application.

Table 2: Seed sowing rates (g/m²).

Turfgrass species g/m²
Fescues & bents 23-30
Perennial ryegrass & other grasses 35-40
Bents (Agrostis spp.) 8-10
Carpet grass (Axonopus spp.) 8-12
Couch grass (Cynodon dactylon) 5-8
Centipede grass (Eremochloa ophiuroides) 1.5-2.5
Red fescue (Festuca rubra rubra) 15-25
Perennial ryegrass (Lolium perenne) 20-40
Kentucky bluegrass (Poa pratensis) 10-15

After sowing, lightly rake over the surface, and water with a sprinkler. A biodegradable paper can be used to cover the newly sown seed to prevent erosion on sloping lawns. Germination will occur in one to two weeks after sowing.

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Vegetative propagation

Lawns grown from most warm-season grasses, or the cool-season creeping bentgrass (Agrostis palustris), which produce stolons and rhizomes, may be established by vegetative means in late spring and early summer. Lawns can be established by a number of methods.

Stolons or runners can be spread evenly over the prepared seed bed, top-dress with sandy soil, roll, then water. Alternatively, stolons or runners can be sprigged by planting them in holes or furrows 25-50 mm deep, 80-150 mm apart, firmed in and watered. Plugs of turf can also be planted at intervals of 25-45 cm.

 

Acknowledgements

Thanks to Bill Walmsley, New Zealand Sports Turf Institute, for his article which was abridged for the section ‘Perennial Ryegrass for Lawns and Turf’, and Sam Wakelin for the drawings in Figure 1, Figure 2 and 3. Thanks also to Robert Lamberts for the photographs of weeds.

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