Congratulations! You’ve just bought the house of your dreams in Iowa City or Cedar Rapids, IA! It’s a great feeling – this is the kind of home you’ve worked for and you just know that you’re going to be happy there. You’re a bit of a lawn nut too, and you’ve stumbled into a property that has an in-ground irrigation system. No more brown or yellow lawn in July and August when things get too dry. You can have a nice, lush, green lawn the whole season, and the title of “Turf King” is in your sights.
Oh, if only it was that easy! Water is essential for all plant growth, we all know this. But did you know that too MUCH water is actually worse for plants than too little? The tendency for homeowners is to water too much. If you water every night, then it won’t go dry! That may be true, but we’ll cover the danger behind that thinking in a bit. Or, the company that installed the system put together a schedule that doesn’t take into account the environment at your property; “factory settings”, if you will. Having an irrigation system can be a major convenience and a beneficial item in the quest for the best lawn on the block. However, they do require constant monitoring and maintenance to make sure they’re doing the job correctly.
Turf irrigation is a broad topic that could fill several hours and many pages of reading material. Turf professionals all across the world spend considerable time on the “simple” act of watering the turf. We’ll try to keep things relatively simple (after all, we’re not hosting Wimbledon or the Super Bowl on our lawns) and touch on the key points that will help you get a grasp of how to make your irrigation system work for you!
So, What is the Right Amount of Water?
In general terms, one inch of water per week is recommended for growing healthy turf. It’s a decent benchmark, but that number should change through the course of the season. When temperatures are cool, daylight hours are short, and if we go through a stretch of cloudy skies, your lawn will need very little water. At the peak of summer heat, one inch of water probably isn’t enough! The best way to determine how much water is enough is to examine the turf itself. Grass has an amazing way of telling us what it needs! This isn’t a difficult thing to do, taking a few minutes to walk across the lawn will give you an idea of what it needs for water.
What do I look for??
Luckily, turfgrass gives us ample warning when it starts to dry out. The first thing we look for is a change of color. The green color fades a bit and starts to take on a grayish cast. As it progresses, it starts to take on a purple cast as well. At this stage, the leaf of the plant breaks and bends easily. Walking on it will leave very noticeable footprints (as shown below). You may notice that the grass has stopped growing in those spots as well. This is the IDEAL time to water. A deep, thorough irrigation the night/morning after seeing turf at this stage will be extremely beneficial, and the best technique for the health of the turf.
If the turf doesn’t receive any water at the above time and goes a few more days without water, the purple cast becomes brown patches. If you pull at the turf in these spots, it will stay in place (meaning that it isn’t some sort of insect chewing at roots). The soil has very little moisture at this point, and a very deep irrigation is needed to bring things back. Watering a few nights per week may be necessary to give the turf enough water so green growth is again visible. Unfortunately, it may take a few weeks for everything to green up if the lawn is allowed to dry out to what is seen below. Once the leaf tissue is dried out, it takes time for the turf to regenerate enough new growth that the damaged turf is mowed off.
Anything past the conditions shown above means the lawn has likely gone into full dormancy. Dormancy means the plant has shut down and is waiting for conditions to be right again in order to revive regular growth. This could take several weeks or more.
Now that we’ve covered what to look for, we’ll discuss what it means to water properly (yes, there is a right and wrong way to water plants). The rule of thumb for turf is “deep and infrequent”. We want to water the lawn thoroughly, with the goal of putting about ½” water on the turf. When do we want to water? We talked about that earlier, we want to water the turf when it gets to the grey/purple stage we showed earlier. That is when the plant and the soil will be most receptive to moisture.
When we talk about amounts of water, it can be confusing because irrigation controllers aren’t adjusted based on amounts, they’re adjusted based on time. How much water is a ten-minute cycle? Is thirty minutes enough? There’s an easy way to find out! You can place a few containers (empty soup cans, Tupperware containers, etc.) in the lawn a few feet apart. They have to be in a spot that is irrigated by one “zone” of irrigation heads, and they have to be the same container to give us consistent readings. A zone is a group of several heads that run at the same time, and water a specific area of the lawn. If you turn that particular zone on for 15 minutes, we can figure out how much water that area is getting in one hour by measuring the average amount of water in those containers and multiplying by 4. For example, if there is 0.2” of water in the container after 15 minutes, then you can expect 0.8” for an hour of operation. It’s expected to have some inconsistencies, but we’re hoping to get a ballpark figure to help guide our watering decisions. The more containers we can use, the better. In that case, running two zones at the same time might be necessary.
Depending on the weather conditions, we may be able to water once a week, or if things got away from us a bit, we might have to water two nights in a row. During a stretch where we’re getting ample rain, we could go several weeks without running an irrigation system. The key to all of this is being able to recognize when the plant needs water, and only watering when needed.
So Why Should We Let It Get So Dry?
When plants are healthy, they grow. Not only are the leaves and “showy” parts thriving, but the roots are growing too. The thicker and deeper the roots, the more efficient the plant is at taking in water and nutrients. Drying the plant out actually encourages roots to grow deeper in search of more water. We starve the plant of water until it shows signs of drought stress, then we give it a thorough drink to quench its thirst. In general, a ½” of water should moisten the soil approximately 6” deep. Maintaining this cycle of deep watering on dry turf will encourage a thicker root system to the point that irrigation becomes even less frequent.
If we water too frequently in small amounts, the roots never have a chance to go searching for water. Shallow root growth is going to lead to many issues and a plant that isn’t healthy. Over-watered turf will take on a bit of a yellow cast and will thin out over time. If the roots shrink, so will the plant. This watering patterns leads to excessive moisture in the thatch layer, which can lead to turf disease. In extreme cases of overwatering, the soil becomes soft and prone to mower damage. Weed infestation becomes possible due to the soil being wet and the plant thinning out. If we enter a period of very hot weather and the soil surface is wet, we run the danger of seeing scalded turf. The top layer of soil turns into an oven, and this deadly combination of heat and moisture literally cooks the roots.
Water is a precious resource, and we don’t want to see any of it wasted. I’m sure we’ve all driven down the street in the rain and noticed irrigation running at a business or home. Those are situations we absolutely want to avoid. There certainly is a responsibility that comes with having an irrigation system. Being armed with the knowledge of proper watering techniques will help your lawn, the environment, and the level of enjoyment from having it. Irrigation doesn’t have to be irritation!