OK, so now it’s on to lawn watering.
Just like with new plants, it’s important to water your lawn efficiently. This will help ensure its overall health and its ability to withstand drought (we get those occasionally here in the NC Piedmont). Efficient watering also saves water and makes us better stewards of our resources—you do know that lawn watering is always the water use people gripe about when water supplies are getting low.
Note—these quidelines are for North Carolina, USDA zones 7-8.
Things to avoid when watering: frequent, light waterings; watering during the heat of the day, evening or night; allowing excess water to run off lawn areas; and overspraying hard surfaces.
Water deeply and infrequently—to get and maintain a deeply rooted lawn you need to get that water to soak into the soil. Fescue lawn roots can go down to 12”, but that’s in ideally prepared soil. I’d aim for 6” depth in our clay to clay loam soils. In sandier soils, go for 12” deep. To get water to soak that deeply you’ll need to apply quite a bit of water.
|Available Water Capacity by Soil Texture|
|Textural Class||Available Water Capacity
(Inches/Foot of Depth)
|Fine sandy loam||1.50–2.00|
|Silty clay loam||1.80–2.00|
In the chart to the right—source here—you can see that clay soils hold about 1-2” of water in each foot of soil depth.
Note that sandy soils hold less water, water just flows right out of this type of soil. That’s wasted water, as far as your landscape is concerned.
So if you need to soak the soil 6” deep and it takes 1.5” of water to soak 1’ of soil, you’ll need to apply about 0.75” water if the soil is completely dry.
But you don’t want the soil to dry out completely. What you really want to do is add more water when the soil moisture gets nearly dry enough to cause wilting without getting that far. You need to replace the soil moisture lost to evaporation and plant transpiration (evapotranspiration or ET). But how do you know how much to replace?
One way is to monitor soil moisture levels. You can use a moisture meter. A metal soil probe can also be used to pull a plug out of the soil and check the moisture. You could even try digging a test hole.
… or you can use NCSU’s TurfFiles Turf Irrigation Management website. Here, you set up an account with information about your property, type of grass and soil. You determine how much water your sprinklers put out (it tells you how to determine this in inches per hour) and you input how much you water. The system uses local weather data to estimate how much water loss occurs in your area and tells you how much more you need to water. You can use this to help you adjust your irrigation controller if you have an automatic system. It is important to know how much each zone puts out over time so you can set the time for each one.
…or if you have an irrigation system, you can replace your controller with a new smart controller that uses weather data to schedule watering all by itself. This is a truly efficient way to run your irrigation system. Old controllers—recently state of the art—allowed you to set up lots of watering programs, but the user has to do all the adjusting. Rain sensors would keep the system from coming on after a certain amount of rain. But they didn’t recognize the levels of solar radiation or the amount of wind, both of which affect evapotranspiration. With smart controllers, you enter the amount of shade, type of plant, amount of slope, type of soil and more information for each zone. The controller takes that info, combines it with the ET information and waters accordingly.
I have clients who installed one of these controllers with their new landscape. It was summer. The clients were expecting their first child and didn’t have time to adjust or even think about their watering. In the fall, I checked their controller. The system that was watering every other day in the summer was now watering once a week, if that much. And their place looked great. All without user input. If these clients had installed a traditional controller, their system would have been wasting tons of water that was obviously not needed.
Avoid runoff—if you have clay soils, you may have soil with a low infiltration rate. In other words the water soaks in slowly. When watering, it is important not to exceed the infiltration rate of your soil or you’ll get runoff. On slopes runoff is even more pronounced. The best way to avoid runoff is to allow some water to soak in then add more water. If you are manually watering with sprinklers, you could water each area just until runoff begins, move it to a new area, then start back at the beginning. You may need to run this cycle several times. If you have an irrigation system, most controllers can be set to run multiple cycles.
Again, those smart controllers do this automatically. Soil type and the amount of slope tell the controller when it will need to soak. On flat, sandy sites, it won’t stop to soak as much as clayey, hilly sites.
Don’t water things that aren’t plants!—it seems obvious, but we’ve all seen water spraying onto a street or walkway. Even watering planting beds with sprays is inefficient. If you water with portable sprinklers, try to choose one that fits the lawn, round for curved areas, rectangular for…well, you get the idea. Automatic systems should be designed to fit the lawn areas. Poorly designed systems generally cost less to install, but are very inefficient and the cost savings will be added to your water bill. If you have such a system, consider having it redesigned. Or a redesign might be needed if you’ve changed your landscaping. Plants installed between a spray head and a lawn area may create a water shadow and part of the lawn won’t get water.
Irrigation heads can move a bit from mower traffic so try to watch them run now and then to make sure you adjust them as needed. Since most systems around here run early in the morning (as they should), you may not see that one’s gone askew.
With a little extra time you can be sure to save water while you keep your lawn healthy and looking great.