Watering Your Lawn.
Probably the most important cultural practices to get right with any lawn is watering. In a perfect world there would be enough rain fall to maintain a lush lawn all year round, but there isn’t and we often need to subsidise the rain fall by various amounts. The amount of water we subsidise depends on a few factors, for example, the type of grass, whether it is a warm or cool season variety, your climate, your soil profile and also you current watering practice. I’ll touch on each of these to explain.
In Australia warm season grasses make up the majority of home lawns for good reason they are suited best to the majority of our regions being a predominantly dry continent. They have a stronger and adapted leaf structure to suit heat stresses, have much deeper roots and a network of stolons and often rhizomes storing energy in or on the protected soil layer under the thick dense leafy canopy.
Because of the warm season grass characteristics, we need to water the lawn to suit its root system, with deep soaking watering at infrequent intervals, meaning not often. The quantity of water required on a weekly schedule should equate to 25-30mm of rainfall in summer, ideally we should be aiming to water this amount once a week. Realistically with various conditions up to twice a week may be necessary delivering 12-15mm with each water. The best of time of day to water is early morning, an hour or two before or after sunrise, a wet lawn for a prolonged time from watering in the evening will encourage disease, only water at night if you feel it will dry during the night. It is okay to give the lawn a needed soak occasionally after a scorching day, as it will likely dry out because of the warmer night and the water will be dispersed.
Warm season grasses can easily cope with the top layer drying out, they deal with some drought stress when well established, in fact this can do them good, and represents the best time to water. It’s actually healthy for the soil to dry out a bit too, soils can become smelly, compact easily and anaerobic if left too wet too long in warmer conditions resulting in disease also.
Cool season are beautiful grasses they can do quite well in a many areas of Australia especially some varieties of Ryegrass and Fescues as their root structure can be deeper than some others. Compared to warm season grasses they are not deep, this results in being very prone to heat stress, not being forgiving if there is a water cycle missed or water shortage, they are demanding on water resources so soil management with amendments often need to be implemented.
Because of the much shallower root systems, there is greater dependence of the top layer of the soil remaining damp, which requires a lot more water by comparison to warm season. This makes the root zone moisture content affected by evaporation and heavily influenced on the daily conditions, coupled with a thinner leaf canopy you may find your self watering on a daily basis in hot conditions with shorter lawns. In warm conditions its not uncommon to water 40-50mm of water over a weekly period, ideally every 2-3 days, but as mentioned earlier nightly during very hot spells.
Water being a limited resource, thought needs to be given to the installation of a cool season surface, as sometimes water restrictions cannot sustain this style of lawn as it can go from lush to severely damaged in a matter of days.
Climate and Soil Profile
Your climate, being your daily and nightly temperatures, also impact the watering of your lawn. Warm days and cool nights lead to increased soil evapotranspiration. Dry, windier conditions are very stressful to lawns with the increased plant evapotranspiration. These are two major contributors to moisture loss in different regions resulting in the need to water different amounts.
The type of soil you have also contributes to the water usage and the availability of moisture to your lawns root system. A silty or clay based soil will retain a lot more water than a sandier profile, however this is not to be confused with the soils ability for water infiltration or penetration. While a heavier clay base soil is capable of retaining the water doesn’t necessarily mean it’s readily available nor easy to wet. Sandier profiles generally will leach and drain water beyond the root zone. The result of these examples may give you the impression of not enough water, as water is running off a clay surface and draining through a sandy profile. Fact is, there is enough water, it’s just not available to the plant.
Soil amendments and products like soil wetters are essential to an even finish, making water uniformly available to the lawn. There are products that aid in water infiltration or penetration, products that aid in water retention then there are product with in the Hydrolink range that that can do both.
A simple test to check your soil moisture is a screw driver test. Using a long screw driver will show you your moisture in your soil. There are even cheap instruments with one, two or three probes measuring the resistance of the soil indicating the moisture a very handy tool if you find yourself guessing.
Dangers of Over Watering
Mainly applying to warm season grasses, it’s easy to be harming our lawn with love and being sucked into thinking more is better as the results are outstanding. This is not the case, our lawns actually learn a bit like ourselves, work hard when we need to and loaf and be lazy when we don’t need too. The same applies to watering your lawn, we mentioned earlier about drier soils, this is part of the reason why. We need to teach our lawns to search for water, same goes for the transition period of a freshly laid lawn through the establishment phase. If we continued to water the same way as we did establishing our lawns where there is near no rooting structure, this is exactly where the roots will stay even with established lawns bottom roots will die off in the cycle if there is plenty of water now in the upper profile.
Measuring Irrigation Delivery
It is important we understand how our irrigation performs, with the evenness of the coverage causing the wetter and the drier areas. Very few residential systems are perfect due to various reasons like yard shape, nozzle selection and water pressure, I do recommend if you are installing it yourself be confident you know what you are doing if not have it at least designed by a irrigation supplier. Often this is a free service if you support them.
The easiest way to measure delivery is to use a series of round tuna tins, place them randomly over your lawn. Definitely placing them in the suspected wettest and driest areas and then in between areas. Run the irrigation for a known period of time then measure the depth of the water in each of the tins, this will give you an understanding of how much water you are delivering per week when you use this information. Multiple tins will also help you balance your system with nozzle selection and adjustment, then will help you monitor if anything isn’t working or is becoming blocked if you do this on a semi regular basis.
So water longer and deeper, less often, manage your soil to reduce run off with either a product to aid infiltration and/or by mechanical means of coring or aeration.
It is very important to get our watering right, and be consistent with it. Shorter roots are less forgiving in times of heat stress, nutrient shortage, disease and insect pressure. Longer roots are on the hardiest and healthiest lawns.