Various cultural practices should be adopted and planning undertaken when irrigating your turfgrass. This will help to improve the quality and health of your turfgrass and more importantly to save you money and the environment, by not wasting water.
Quick facts on lawn watering:
The quality of most lawns is only affected when they start to show symptoms of wilting or drought stress. During the latter periods, the grass blades turn bluish-purple, or grey and the leaves begin to wilt. Leaves fold or roll along their length. Footprints also remain in the lawn for several hours. Leaves with plenty of water quickly return to their rigid upright shape, while leaves lacking water will remain trampled for a period of time. If high temperatures and dry conditions continue without rain or irrigation, the above-ground tissues of the plant material will brown and die. Variation may be seen because of micro climates or variation in soil type or depth. Recovery will be largely dependent on the turf species you have and if the turf grows be either stolons and/or underground rhizomes.
The best time to water a lawn is between the hours of 4:00 AM and 8:00 AM. During this time, the water pressure is highest, disruption of the water pattern from wind is low, and water lost to the atmosphere by evaporation is negligible. Watering early in the morning also has the advantage of reducing the chance of turf diseases that require extended periods of leaf moisture to provide optimum conditions for onset. Avoid irrigation at midday and during windy conditions.
You only need to water the lawn when it shows symptoms of stress. This could be after a week during hot weather, or after 2 to 3 weeks during cool weather. Critical factors are the effective rooting depth of the lawn and the moisture holding capacity of the soil. The objective is to apply enough water with each irrigation to soak the soil to a desirable depth of approximately 150 mm to 200 mm.
Water should also not be applied at a rate that is higher than the soils infiltration rate i.e. capacity to drain. Sand normally absorbs water quickly. An exception to this rule are dry hydrophobic sands, which are coated in a layer of organic matter that repels moisture causing water to run horizontally across the soil surface. Products are available at to treat this condition.
Clays are thirty times slower than sands in accepting applied moisture. If water is applied too quickly to these soils it is wasted, becoming runoff. Such soils respond best to light sprinkling over a longer period of time.
Unlike warm-season turf species, cool-season species are often shallow rooted and do not extract deeper soil moisture. They also use different biochemical pathways that are less water efficient. The following table provides some general guidelines on the likely minimum weekly water use in mm for barely acceptable growth by cool- and warm-season turfgrass species in Australia’s capital cities. The figures (in millimetres) are based on average daily evaporation data acquired from the Australian Bureau of Meteorology (BOM) multiplied by a crop factor figure obtained from Handreck and Black (2010) for warm- and cool-season turf and will vary around the mean. It is important to use daily evaporation, not annual data as variation (between the 10th and 90th percentile) is significant.
Continue to monitor the lawn and be on the lookout for areas that are soft and produce squashy footprints when walked on. If rainfall occurs, delay your next scheduled watering and continue to look for the early symptoms of stress or decreasing soil moisture content within your soil rootzone.
Some other useful tips include:
Properly designed and operated automatic irrigation systems with pop-up sprinklers can supply water uniformly over an entire area without wasted runoff. However, the most common type of watering occurs with hose-end sprinklers. Some studies have shown that the average homeowner applies 2.5 times the amount of water that is required for turf growth when using hose-end sprinklers. There are several types of systems available. Select one that best fits your size and shape of lawn and then operate it efficiently. All hose-end sprinklers can be attached to an inexpensive timer that can be used to shut off unattended sprinklers and avoid over-irrigation.
Some sprinkler types and their applications
Before deciding what sprinkler type is for you, undertake a pressure test before purchasing or installing an irrigation system. This is a particular issue when running of mains or when water pressure is ordinary.
Officially, greywater is domestic waste water from baths, showers, basins, laundries and kitchens, but not water from toilets. Greywater generated from the kitchen, swimming pools and spa pools should not be reused for irrigation.
Depending on your state and council water regulations, greywater can be reused to water turfed areas by connecting a flexible hose to a washing machine outlet; or via a council approved greywater diversion device or treatment system installed by a licensed plumber.
Greywater can’t be stored on-site for more than 24 hours unless it has undergone treatment in an approved system. Always check with your local council before purchasing and installing diversion devices or treatment systems to make sure your location is entitled and to ensure you have the correct permits in place.
Some of the components found in greywater (water, salts, nutrients) have no adverse effects on turfgrass or plants; and in many cases, they can even prove beneficial for their growth. An example of this is nitrogen, a key nutrient for plant growth which is commonly supplied in greywater.
There are some cases, however where greywater contains chemicals in high concentrations that may be inhibiting to turfgrass development depending on the concentration in the detergent, what exists in your soil and your soil type. An example of this is sodium. The chemical composition of the laundry detergent may not be clearly evident on the product label. However, you can obtain such information from the Lanfax Laboratories (www.lanfaxlabs.com.au) which has undertaken several independent studies which were undertaken in collaboration with Consumer Choice.
Greywater contains salts from laundries which can be substantial, particularly in the wash water which is different to the rinse water. Application of poor quality greywater without dilution may cause damage to some turfgrass species and to the soil itself, particularly high clay soils, which may result in soil structural degradation. Regularly changing the location where the greywater is applied will reduce the risk of adversely affecting the turf and or soil. Rainwater can also help to flush accumulated salt from within the soil and gypsum can also help to remove excess sodium from soils. If damage is observed to the turf or soil, use of the greywater should be stopped immediately and specialist advice sought.
Newly turfed or seeded lawns require special attention and irrigation. Follow these tips below to help your investment flourish after you have already done all the hard work.
Newly turfed lawns require watering once or twice a day. Begin irrigation immediately after laying a section of turfgrass, even before completing the entire project. Plan your planting to work in conjunction with the operation of your irrigation system and make sure that the irrigation water is not flowing across the surface area where your access is or where you are turfing.
Turf should be well watered so that the sod strip is wet as well as the top 25 mm of soil underlay. The first irrigation will take about 25 mm of water to achieve complete wetting of the turfgrass and this may vary depending on the soil type from where the turf you purchased was supplied. After watering, lift corners of the turf up at intermittent locations to determine if it has been adequately irrigated.
Continue watering one to two times a day with light irrigations to prevent wilting and to ensure a moist soil just below the turf layer. This should be undertaken for at least one week.
As sod becomes established and roots penetrate through the soil surface, gradually reduce the frequency of watering but wet the soil deeper. After the turfgrass has been mowed two or three times, deep, infrequent watering should be practiced. During hot, windy weather, establishing sod may require several light mistings per day to prevent wilt and potentially lethal temperatures. In this case, light misting, just to wet the leaf surface and not to supply water to the soil, cools the grass as water is evaporated from the leaves.
Do not over-irrigate (saturate) the soil because that will inhibit the roots from growing into the soil as a result of anaerobic activity (wet and rotten egg smell of the soil). If the turfgrass cannot be watered on a daily basis, thoroughly water the sod and soil to a depth of 150 mm. This will delay the rooting time of sod but will reduce the chance of rapid drying and severe loss of any turfgrass.
A newly seeded lawn should be watered daily and may need as many as 3 to 4 light waterings in a single day. Keep the seedbed moist, but not saturated to a depth of 25 mm to 50 mm until germination occurs. Expected germination times should be written on the package; if not, research such details.
Seedlings of a new lawn must not be stressed to the point of wilt. Continue with light applications of water — 3 mm to 6 mm — 1 to 4 times a day. Watering with a light mist is best for establishing new lawns. As seedlings reach 30 mm to 50 mm in height, gradually reduce the frequency of watering and water more deeply. After the new lawn has been mowed two or three times, deep, infrequent waterings are recommended
Content included on this page has been modified; original content was published in Lawns and Lawn Care, a homeowner’s guide (no date); Gardening with grey water and on the web by the former Dept of Primary Industries and Fisheries. Permission for use has been granted by the now Dept of Agriculture and Fisheries.
Handreck, K. and Block, N. 2010. Growing media for ornamental turf and plants, University of New South Wales Press Ltd, Sydney, NSW.