Do Arkansas Lawns Require A Lot of Water?

By Doug Karcher, Ph.D., Professor, University of Arkansas

There are a few things that turf enthusiasts can count on each spring, like fescue lawns looking brilliant in the landscape, large patch and spring dead spot showing up in wet or cold environments as our warmseason grasses green up, the need to tune up our mower engines and sharpen blades, and unfortunately, the publication of anti-turf articles in the popular press. Like clockwork this month, it was when I was changing the spark plug and sharpening my mower blades to keep up with my fastgrowing fescue lawn that I noted lower than normal spring dead spot occurrence on the north-facing, low-lying bermudagrass areas across the street, and then received a text message from a friend outside of the turf industry with, “Your thoughts?” and a link to a CNN article. The article was titled, “Designing an end to a toxic American obsession: The Lawn” (published April 17, 2020). This article contended that lawns are a big waste of space and water that should be converted to food production and wild-flower areas. Each spring when reading these types of articles, I find it very frustrating that several unsubstantiated claims are made (citations or references rarely included), and as the same outrageous claims are repeated from year to year, no effort is made at offering a counterpoint from turf industry professionals. I first noticed this trend in May of 2014 when the New York Times published, “The Toxic Brew in our Yards”. And, as of this writing, the New York Times has very recently recycled much of that story as, “America’s Killer Lawns”, which was published on May 18, 2020.

The two most common inflammatory implications from these articles are 1) that homeowners apply 10 times more pesticides per acre to their lawns compared to farmers and 2) that lawns require more irrigation than any other agricultural crop. The pesticide use claim seems to have originated from a U.S. Fish and Wildlife publication on protecting frogs, with no data or references included for substantiation. I’ve called the U.S. Fish and Wildlife Service to get info on the basis of the claim but have only been

able to leave messages and my calls have yet to be returned. I am not aware of any such claim being published in the peer-reviewed, fact-based literature. The water requirement claim is likely a misinterpretation of a journal paper published by Milesi et al. (2005) that assumed if 100% of the total area in the United States covered in turf (which they estimated to be about 40 million acres) was irrigated with an inch of water per week throughout the season whenever minimum temperatures were above 40 degrees (late March to early November in Arkansas), only then would turfgrass be the single largest irrigated crop in the country. Unfortunately, that paper was interpreted as, “Residential lawns cover 2% of US land and require more irrigation than any agricultural crop grown in the country” in the latest CNN article. And this is why I have palm imprints on my forehead a few times each spring.

Our industry often gets an undeserved “black-eye” with regard to water usage, which has led some municipalities and even the EPA to encourage the removal of turf areas in lawns and replacement with other landscape plants in the name of water conservation. Obviously, that is not good for our industry and from a water-requirement standpoint, it simply does not make sense in a humid climate. We receive 40 to 60 inches of rain annually in Arkansas, which can easily sustain our turfgrass species with no additional irrigation because contrary to popular opinion, turfgrass species are by nature drought tolerant.

The turfgrass species we utilize in our lawns evolved naturally over many millennia in geographic regions around the globe where water was limiting, either due to limited rainfall, sandy soils, or shallow soils with low water-holding capacity. Essentially, grasses evolved where water-loving trees could not. If you don’t believe this and need more convincing, then head west on I-40 into Oklahoma and observe how the natural landscape changes from trees to grasses as average annual rainfall drops from 40 to 30 to 20 inches. Because of evolution under droughty conditions, turfgrass species do not respond well to excess water.

Lawns that are irrigated too frequently will remain wet near the surface, resulting in a shallow root system that will be less drought tolerant later in the summer. In contrast, as non-irrigated soils dry in the spring, turfgrass roots extend deeper into the soil to access the available moisture there, which results in a much better developed root system and better summer drought tolerance. A lawn with deeper roots will not only be more drought tolerant but will also have better recuperative potential in case of injury due to insects, disease, or traffic.

With the arrival of warmer weather (hopefully!) this month, it’s likely that many Arkansas homeowners, commercial properties, and municipalities will fire up their irrigation systems to water the lawns. Although it may be getting hotter, it probably isn’t quite time to be irrigating home lawn turf. As of this writing (late May) most lawns in Northwest Arkansas will not need supplemental irrigation for at least a couple of weeks as our soils have plenty of moisture to maintain turf growth throughout the rest of this spring. In addition, there is no drought stress anywhere in the state according to the Untied States Drought Monitor (Fig. 1; https://droughtmonitor.unl.edu/) and rains are forecasted for the next several days. In fact, I never advise homeowners to begin watering their lawns based on a calendar date, rather I advise them to hold off irrigating until some visible wilting is present on the turf. Historically, this has typically occurred in late June on my lawn in Fayetteville; however, we’ve had so much timely rainfall in Arkansas the past two seasons that my irrigation requirements have decreased significantly, and I’ve irrigated my lawn only a couple of times since 2017. And 2020 is shaping up to be another wet year.

Fig. 1. United States Drought Monitor conditions as of May 18, 2020. With the consistent spring rains this year, none of Arkansas is undereven mild drought at the time of this writing.

If you’re like many of my neighbors you may ask, “what’s the harm in irrigating lawn turf now?” After all, if you’ve invested in a nice irrigation system then you probably enjoy watching it run. Well, here are a few drawbacks of over-irrigating your turfgrass systems:

1.) Less Healthy Turf.

See the section above on turfgrass evolution and drought tolerance. In addition, turfgrass systems that are kept wet tend to have more disease and weed pressure, are more likely to develop excess thatch, and are more prone to soil compaction.

2.) Expensive Water Bills.

Although I consider Fayetteville city water a bargain at less than a cent per gallon, irrigation costs do add up when considering how much water it takes to effectively irrigate a home lawn. When irrigation is necessary, we generally recommend applying 1 inch of water per week in two to three applications. It takes 27,000 gallons of water to apply an inch of water to an acre, so a medium sized, quarteracre lawn would require 6,750 gallons weekly to irrigate, ultimately adding around $150 to the monthly water bill.

3.) Public Perception.

I’m particularly sensitive to this final negative consequence of over-watering lawns. Home lawns are often the target of public criticism as being “water wasters” when, in reality, turfgrass species are among the most drought tolerant plants used in the landscape. Nevertheless, we repeatedly see CNN and New York Times articles such as those mentioned above. Unfortunately, the myth that lawns require constant watering is perpetuated by too many irrigation systems that are either running too early in the growing season, run too frequently, or run during or shortly following rainfall events (Fig. 2).

Fig. 2 A. Water is sometimes wasted on lawns, but this is caused by operator error, not heavy water consumption by turfgrass species. Here, irrigation run times are too long on this sloped campus lawn causing water to run to down the street.

Fig. 2 A. An automatic irrigation controller is watering this commercial property during a rain shower.

Let’s discuss the best way to utilize those automatic irrigation systems. My best advice is to turn the main dial to “OFF” (Fig. 3) so that your irrigation programs do not continue to run unnecessarily. Then, set up a program that will apply enough water to wet the soil to a 3 to 4 inch depth (this typically takes 0.5 to 0.75 inches of water for Arkansas native soils, which will require run times of 30 to 60 minutes per zone for most residential systems). Then, set the program start times daily for the early morning hours to ensure that the program will run every morning when the main dial is switched “on”. This may seem counter-intuitive at first but remember that the main dial should be set to “off”. Finally, wait until you see some visible drought symptoms in your lawn (remember, a little drought stress will ensure a deep root system) and then turn your program “ON” or “RUN” so that it runs the next morning… and then don’t forget to return the dial to the “OFF” position when the program has finished.

Fig. 3. My favorite setting on the automatic irrigation controller is “OFF”. Unfortunately, this setting is under-utilized by many homeowners.

The above strategy takes advantage of your automatic irrigation system’s capabilities while eliminating the possibility of over-watering and all the related negative consequences discussed previously. One exception to delaying lawn irrigation for now is if you are establishing turf from seed, sprigs, or sod (Fig. 4), which all lack an extensive root system and cannot access moisture deeper in soil.

Fig. 4. This bermudagrass sod was laid near campus in May 2014 and was not irrigated. Although there was some moisture in the underlying soil, it was unavailable to the new sod, which lacked a root system. Unlike mature turf, new planted sod, sprigs, or seed may require spring irrigation in the absence of daily rains.

For those of you that want to take some extra steps in conserving water while maintaining your lawn, here are some additional considerations:

• Use improved irrigation controller technology. Many newer irrigation controllers can utilize rainfall or soil moisture sensors, or even weather data to adjust programs so that water is only applied when needed. Recent research completed by Dan Sandor while earning his Ph.D. in our turfgrass science program indicated that soil moisture sensors used only 1/3 the amount of water compared to “set-itand-forget-it” weekly irrigation program. Even more impressive, Dr. Sandor (now an Assistant Professor at Virginia Tech) showed that such water savings were consistent over three consecutive years with no reduction in lawn quality, and that a complete return on investment of such technology was achievable in a single growing season. With soil moisture sensors, we can fully utilize the set-it-and-forget-it appeal of automatic irrigation systems without wasting water.

• Use a drought tolerant cultivar. Recent research has identified turfgrass varieties that exhibit superior drought tolerance characteristics. Cultivars of tall fescue, bermudagrass, and Kentucky bluegrass have been experimentally proven to retain their green color longer during extended drought conditions. More information is available at www.tgwca.org.

• Grow deep roots. In addition to allowing the soil surface to dry, deep turfgrass roots can be produced with good mowing and fertility practices as well as core-aerifying areas where the soil has become compacted. The University of Arkansas Extension has several great publications packed with tips for maintaining healthy lawns with a deep root system. These may be found at: https://www.uaex.edu/ yard-garden/lawns/default.aspx.

To conclude, I’m a bit fed up of reading about toxic lawns the waste water in the popular press, so let’s make sure we’re all doing our part to irrigate only when necessary and not flame the fires of this myth. •

REFERENCES

Lewis, D. 2014. The Toxic Brew in Our Yards. The New York Times. Accessed 26 May 2020 https:// www.nytimes.com/2014/05/11/ opinion/sunday/the-toxic-brew-inour-yards.html

Milesi, C., S.W. Running, C.D. Elvidge, J.B. Dietz, B.J. Tuttle, and R.R. Nemani. 2005. Mapping and Modeling the Biogeochemical Cycling of Turf Grasses in the United States. Environmental Management Vol. 36, No. 3, pp. 426–438

Ponsford, M. 2020. Designing an end to a toxic American obsession: The Lawn. CNN Style. Accessed 26 May 2020 https://www.cnn.com/style/ article/lawns-american-yard-us

Renkl, M. 2020. America’s Killer Lawns. Accessed 26 May 2020 https://www.nytimes.com/2020/05/ 18/opinion/lawn-pesticides-insectextinction.html

Sandor, D. 2018. Water Conservation Practices for Irrigation of Turfgrass Lawns. Theses and Dissertations Retrieved from https://scholarworks. uark.edu/etd/3064

U.S. Fish and Wildlife Service. 2000. Homeowner’s Guide to Protecting Frogs. Accessed 26 May 2020 https://www.fws.gov/dpps/ visualmedia/printingandpublishing/ publications/2003_Homeowners GuidetoProtectingFrogs.pdf