Irrigation water management should promote a rich development of the root system ...
Irrigation water management is essential to support natural grass growth during dry periods and hot summer days. Proper management is sufficient to provide the necessary moisture and save the most precious resource.
There are two rules for watering the lawn regularly: a) water at long intervals during the early morning hours using the system only if the lawn begins to show signs of water shortage (it starts to become less resilient) and b) ensure that the moisture content of the soil is kept at a low level, above the grass wilting point and avoid saturating the soil with water during hot periods that exceed 25°C for cool season grasses and 35°C for warm season grasses. Irrigation management aims to strengthen the cell membrane and improve the ability to hold water within the cells compared to any other technique that is often difficult to practice such as 'syringing' (source Test in Japan). It is advisable to carry out a complete soil analysis and check the maximum amount of water the soil can hold which is called field water capacity as well as the wilting point the amount of water that is still contained in the soil but not available for grass growth, to better understand how to manage the irrigation schedule according to changes in evapotranspiration.
Having a modern ad hoc system allows you to automate the management with an easy-to-use control unit.
We hereby indicate some strategies to reduce water consumption and keep the existing lawn healthy.
Rainbird sprinkler installed at San Siro in 2012
Only water when the lawn needs it. Water conservation is not the only reason to limit the amount of water you give your lawn. Over-watering is bad for the health of your lawn and can contribute to the development of fungus and disease. Some types of grass require more water than others, and environmental factors such as temperature, humidity and wind can greatly influence how often you water your lawn. Fortunately, the most accurate way to determine whether your lawn needs water is also the easiest: just look at the grass:
- Water deeply to encourage deep root growth. Frequent shallow watering encourages weed germination, and also stimulates grass roots to grow above ground, exposing the plant more susceptible to drought and certain diseases. Watering only when your lawn really needs it encourages the roots to grow deeper, but only if you provide enough water to penetrate the root zone with each watering.
- The most accurate way to determine the depth of the root zone is to dig a small hole and measure how far down the roots go.
- Alternatively, you can follow these general guidelines: If you have a Poa Pratensis lawn, each irrigation should moisten the soil to a depth of 15-20 centimetres, whereas for most other grasses, the water should penetrate 20-30 centimetres. You can determine how long to leave the irrigation system running by using one of the following methods:
- Start the sprinklers for 15 minutes. After 18-24 hours, check the depth of the soaked water by digging a small hole in the irrigated area or using a probe (the probe will easily push through the wet soil). You can also push a shovel into the ground and use it as leverage to move the soil enough so that you can observe several centimetres below the surface. Once you have checked how deep the water has penetrated in 15 minutes of watering, you can calculate how long you need to leave your watering on.
For example, if the soil is moist at 10 centimetres below the surface and your goal is to moisten the soil to a depth of 20 centimetres, you will need to leave the sprinklers on for 30 minutes (2 x 15 minutes) each time you water.
- Estimate the amount of water you need according to the type of soil. In general, 2.5 cm of water will penetrate sandy soils at 25 cm, medium soils at 15 to 20 cm, and clay soils 7 to 10 cm. Using these estimates is not as precise as digging, but it is very close, especially if you have a good knowledge of soil composition. To figure out how long you need to keep your sprinkler or irrigation system going, calibrate your sprinklers.
- Water early in the morning. When using sprinklers, some of the water evaporates before it touches the ground. On a hot, windy day, the amount of water that never reaches your grass can be substantial. To reduce evaporation losses, water from 4 a.m. to 9 a.m. when the temperature is still cool and the wind is usually calm.
- Avoid watering the lawn with hot water. On hot days, the water inside the hose can become very hot from the sun's energy - hot enough to scald! It is better to skip watering that day, and water early the next morning. Run the hot water through the hose after the sun has gone down, to empty the hot water.
In this way the plant grows deeper, the lawn becomes more resistant to environmental stress and foot traffic.
Monitoring water management well during the warmer months is crucial as it is the essential element for turf metabolism.
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