Healthy Lawns Advice

The aim of fertilising is to produce a vigorous sward of grass, or more properly, a grass that has a vigorous root system to at least 100mm in to the soil. The best strategy for turf nutrition is to supply the grass with adequate levels of all nutrients except nitrogen. Growth is then controlled by application of nitrogen in amounts just sufficient to provide an acceptable appearance.

High levels of phosphorus are unnecessary and waste money. More importantly it may cause iron deficiency and encourage the growth of weeds such as winter grass (Poa annua). Phosphorus stimulates grasses into producing seed – the last thing that is wanted in a lawn. Excessive phosphorus causes potassium imbalance and stunting of root growth. Fescues dislike quite small amounts of phosphorus and die out as the phosphorus level in the soil increases.

Potassium is an essential nutrient, valuable for turf because it toughens the leaves so that they are more wear and disease resistant. It promotes the storage of carbohydrates in the roots, and has an essential role in regulating water loss through transpiration. Extra potassium applied in autumn when the grass is going into dormancy will help it survive through winter and enhance its ability to grow quickly in spring.

Iron is the trace element most often in short supply in turf. Deficiencies are associated with high soil pH, excessive applications of phosphorus, waterlogging and excessive thatch.

Other trace elements needed by turf grasses are manganese, magnesium, and copper. Symptoms of deficiencies are reduced growth and paleness of the grass. The turf will look sparse and weak when the nutrient deficiencies are severe.

The goal of any fertilisation program is to provide the lawn with the nutrients it needs for optimum growth. The most accurate way to find out those needs is to have the soil tested. The soil is the conveyor of the nutrients to all the plants in your landscape. Soil test kits are generally available at better lawn and garden centres. Soil test services and information are generally available from private labs found in the Yellow Pages of your telephone directory. If your lawn hasn’t had a soil test in the last 3-5 years, seriously consider having one done. If a soil test is not conducted, follow these general fertilisation guidelines.

Most lawn experts agree that fertilisers with N (Nitrogen), P (Phosphorus), and K (Potassium) analysis ratio of 3-1-2 or 4-1-2 are acceptable for use on any lawn. They also agree that the fertiliser should have at least one-half of its N (Nitrogen) in a slowly soluble/slow-release form, ie. natural organic, sulfur-coated urea, resin-coated urea, ureaformaldehyde, methylene urea, or I.B.D.U. Lawns fertilised with one of these slow-release forms tend to have better colour, thickness, and reduced leaf growth. Fertiliser application rates should be as low as possible and still produce a high quality lawn.

If the amount of nitrogen (N – the first number of the analysis on the bag) is between 5 and 12, the application rate should be 4 kg per 100 sq. m. If the number is between 13 and 18, the rate of application should be 3kg per 100 sq. m. Anything over 19 should be applied at 2kg. per 100 sq. m. This is a good “rule of thumb”, but always apply the fertiliser at the recommended rate listed on the bag.

The best time to fertilise your lawn is when it’s actively growing and in need of nutrients. This means beginning the program about six weeks after spring green-up and stopping about one months before the first frost in early winter.

When the cool weather returns in autumn, the lawn should again be fertilised. A late autumn application has been shown to increase lawn quality the following spring. Fertiliser application dates and frequency are based primarily on which form of nitrogen the fertiliser contains. Those that have at least one-half of its nitrogen in slow-release form should be adequate for 6 to 8 weeks. If the lawn still has good colour and is growing well at the end of this period, then delay the next application a little longer.

For most of us, it’s the cheapest and most beneficial thing you can do to our lawn. However, watering is the most misunderstood factor in a lawn maintenance routine. The goal of irrigating your lawn is very simple: to replace the moisture that is being lost due to evaporation. Any more or any less will cause the lawn to suffer in times of stress. Generally, given our weather patterns, it is not necessary to irrigate the lawn on a regular basis until October or November.

How much?

The technique of determining how much to water your lawn is simple: Place a small rain gauge or jam tin on the lawn when your sprinkler is running and see how many minutes it takes to fill the gauge to a level of 25mm. Then, over a period of days, see how long it takes for the 25mm of water to evaporate out of the gauge. This will tell you when and how much to water. You may be surprised!

When?

The time of day makes a difference. One basic rule: water your lawn when the least amount of water will be lost to evaporation. Watering early in the morning before the heat of the day will make sure your water goes down to the roots instead of going up in vapour. Avoid watering during the middle of the day when the heat is highest.

How often?

Be sure to follow the “25 millimetre” guide described above. Frequent, but shallow, watering causes the grass to send roots up to the surface looking for water, where they will suffer more during hot spells. Water longer in each spot. Also be sure to water more along paths and kerbs. These areas dry out faster due to more heat build up.

Train your lawn to become more drought-tolerant. Forget about watering the lawn once a week (or every three or four days on sandy soil) regardless of whether the water is needed. Wait till the top few centimetres of soil is completely dry. This is easy to check with a garden trowel. At this stage, hold back on the water, check the blades of grass each day and wait until about one-third have started to wilt. Early next morning, give the area a good soaking. Repeat this checking performance but each time wait an extra day before watering.

Within a few weeks, the lawn will have developed a deeper, more extensive root system that is capable of absorbing moisture from well below the previous root zone.

By the end of summer, you should have extended the time between watering summer-active grasses, such as couch, buffalo and kikuyu, from once a week to every 10 to 14 days and possibly longer. Even some of the traditional but waterholic lawns, containing fescue, Kentucky bluegrass and ryegrass, can be trained to get by for three or four extra days between watering

A word to sprinkler owners

Become familiar with how your system operates! It is very important to “calibrate” your system so that your lawn is being watered correctly for each zone. Do not set the sprinkler system so that all zones are running the same length of time. This will surely be incorrect and will waste water and promote plant diseases. We also recommend not watering your lawn every day on an automatic system.

A lawn can mean different things to different people. It may be a showpiece for your property, a foil for flowering shrubs and annuals, a piece of grass on which to sit, an area for children’s play,or just something to keep down the dust. Whatever your lawn means to you, you will need to spend time maintaining it. Even, if like most gardeners, you are content if your lawn grows reasonably well and is not too overrun with weeds.

If you want to go further and achieve the perfection of a velvety smooth, immaculate lawn, you will need to put in a great deal of time and effort.

Most weed problems arise from too close mowing or scalping the lawn. Weed infestation will also occur where grass is struggling under shade from trees or the variety of turf does not suit the climate.

Never remove more than one-third of the green leaf blade at any one cutting. Short tops tend to have sparse root systems with diminished food reserves. Hard mowing removes part of the ability of grass to make sugars and will severely drain food reserves. If there are no food reserves the grass will be weakened.

It is better to water heavily and less often. Heavy, infrequent watering encourages deep rooting of grasses that are better able to withstand drought. Grass that is watered heavily every week or ten days will be much stronger and healthier than grass that is given a daily sprinkle. Lawns are sometimes killed with kindness by over enthusiastic watering. In an attempt to have the perfect emerald green lawn some people keep on watering and watering. You may get away with it on pure sand but otherwise the soil becomes waterlogged and the roots rot. To improve conditions you need to get the right balance of air and water in the soil by using a coring machine.

The warm-season grasses are much more efficient at using the water to make growth. Couch grass is more than twice as efficient at using water than perennial ryegrass, and nearly twice as efficient as tall fescue (Handreck and Black p294). The amount of water needed to maintain an acceptable turf of warm season grasses is about half that needed for tall fescues and other cool season grasses.

Overwatering and overfertilising with nitrogen-rich fertiliser coupled with infrequent mowing makes the lawn spongy. Thatch is a layer of dead grass that accumulates below the green tops and can prevent irrigation water from reaching the root zone either by becoming water repellent or by forming a dense mat. Thatch is definitely not beneficial to turf because

• scalping is easy when the mower sinks into the spongy layer.
• thatch can harbour pests and diseases that damage turf grasses.
• thatch reduces the tolerance of turf grasses to heat stress and cold damage.
• thatch prevents water from reaching the roots.

Sensible turf management can reduce the buildup of thatch by:

• keeping water supply as low as possible for the appearance needed.
• keeping nitrogen applications as low as possible for acceptable growth and appearance.
• mowing more frequently at the optimum height for the turf grass species.
• removing clippings that add to thatch.

Buffalo, kikuyu, bent grass and couch hybrids such as Santa Ana are especially prone to thatching. Some may need to be dethatched each year using a scarifier or vertical mower. Scarifying is best carried out when the grass is capable of rapid recovery in late spring to mid-summer – October to January.