| Management of turf ryegrass |
| Maintaining a desired height |
| Cutting height and frequency |
| Lawn clippings and mulching |
| Fertiliser |
| Watering |
| How much? |
| Turf aeration |
Routine care of grass lawns and turf
Perennial ryegrass is best adapted to medium-textured, silt loam soils and clays. It survives summer drought best on heavy soils but is often killed on light sandy or gravely soils.
Regular cutting of the grass encourages tillering of the plant to create a dense, healthy sward with an even, attractive finish.
For the first cut of a new lawn, cut the grass when it reaches 5 cm, to a height of 2.5 cm, and gradually lower the cutting height in subsequent mowings until the desired height is reached.
For high-quality lawns, cut the turf to 1.5 cm as needed throughout the year. For utility lawns, cut the turf to a height of 4 cm as needed in winter, and to 2-3 cm on a weekly basis during spring and autumn.
Rule: Mow when the grass has grown by 50%, so you don’t have to cut off more than one-third of the blade.
If the lawn is less than 70 mm in height, grass clippings can be left on the lawn after cutting, rather than removing them with a catcher. The clippings decompose quickly, returning nutrients to the soil within two weeks after mowing. The amount of nitrogen returned to the soil is as much as 88 kg/ha. Since nitrogen is the most expensive component of all lawn fertilisers, it pays to leave clippings.
Clippings also enhance the habitat for beneficial microorganisms and earthworms.
Regular applications of fertiliser ensure a vigorous healthy lawn. Most of the nutrients essential for growth are plentiful within the soil, except for nitrogen (N), phosphorus (P), potassium (K) and iron (Fe). Nitrogen-deficient grass is yellow-green, and lacks vigour.
Nitrogen produces deep green leaves, rapidly growing leaves and shorter roots. Phosphorus facilitates metabolic functions plus energy storage and use. Potassium is used to create cell components, and it helps regulate respiration and transpiration. It helps the plant grow, withstand environmental stress and resist disease.
Two applications of fertiliser a year are sufficient. Apply in late spring and early autumn. Nitrogen applied in summer may stimulate lush growth and encourage diseases.
Thatch can be a problem on a lawn that is intensely fertilised and watered or on a lawn that receives infrequent cutting. Pesticide use is also implicated.
Established turf generally withstands dry periods, but growth is retarded. Under drought stress, turfgrasses dry up and the leaves roll and turn a dull purplish colour, a process called dry wilt. However, too much water may induce wet wilt, which occurs when the soils become saturated, and the movement of oxygen into the soil and carbon dioxide out of the soil ceases.
Water any turf just before it begins to wilt. This stage can be recognised because the grasses develop a dull purple cast, and the leaf blades begin to roll or fold. Further, the grass does not spring back after the lawn has been walked on.
Preferably, water early in the morning when conditions are calm and temperatures are low, so less water is lost to evaporation. Watering in late evening has the additional benefit of reducing water loss to evaporation, but because the grass usually stays wet all night, watering at this time can induce disease outbreaks.
Water to a depth of 10-15 cm. Deep watering encourages development of an extensive root system, enabling the plants to utilise nutrients and water in the soil more efficiently than shallow root systems.
General guide: Turf needs about 21 mm of water once a week during summer, with a supplementary irrigation at noon during hot days.
Aeration of the soil allows deep root growth, enhances establishment, and reduces soil compaction and excessive thatch. Methods of aeration include scarifying, slitting, hollow tining (coring) and spiking. Aerate during spring and autumn. Dry summer conditions make the turf more susceptible to drought.
- Scarifying – Scarifying removes thatch, permitting air to enter the lawn surface and enhancing thatch degradation by micro-organisms. Rake the lawn with a wire or spring-tined rake, or a powered scarifier, in two directions, one at right angles to the other. Moss should be killed prior to scarifying to prevent it spreading to other parts of the lawn during scarification.
- Slitting – A slitting machine comprises flat knife-like blades that cut slits through the thatch to a depth of 8-10 cm, allowing air into the soil.
- Hollow tining – A mechanical or hand tiner removes cores of grass, thatch and soil, making a series of holes across the lawn about 10 cm apart. The cores need to be filled with a sandy top-dressing to prevent them from closing.
- Spiking – Achieved by using a mechanical or hand spiker or roller aerator, or a garden fork. Angle the spikes back slight to raise the turf gently, to encourage deep root growth by creating fissures in the soil.