August 30, 2007
Some Arkansans were fortunate to receive rains this past weekend to help green up their turfgrass. However, some Arkansans are battling the effects of drought. The maps below show our current drought conditions as well as the forecast for drought throughout the remainder of the fall.
Below are some facts about drought supported by research but also some statements that are supported by experience and anecdotal evidence where appropriate.
•Though turfgrasses perform best with enough regular irrigation during the summer to keep them green and growing, they are very capable of surviving without rain or irrigation.
•Turfgrasses perform much better under slightly dry conditions than under wet or saturated conditions.
•Turfgrass dormancy (brown turf) is a survival mechanisms allowing survival up to up to 5-8 weeks without irrigation/precipitation without significant thinning upon recovery from dormancy. This would be under ideal conditions of no regular traffic, good soil, moderate temperatures, no shade, minimum thatch, etc. However, survival is affected by species, age, shade, maintenance (low mowing and/or scalping, too much nitrogen fertilizer in spring, not enough in fall), traffic, heat, etc., etc.; so optimum survival may not occur on your particular area.
The relative ability of various grasses to withstand drought is often the subject of debate among turfgrass experts. Bermudagrasses survive dry soil conditions better than most turfgrasses. Research shows that ‘Midlawn’ bermudagrass requires less irrigation than ‘Meyer’ zoysiagrass in the transition zone. Both bermudagrass and zoysiagrass need less irrigation than tall fescue. Turfgrasses become semi-dormant under drought conditions and then regenerate from crowns, stolons, or rhizomes when moisture becomes available. Bermudagrass and zoysiagrass are considered to be fairly drought tolerant but need 1.0 to 1.5 inches of water per week to maintain growth during dry periods. Centipede and St. Augustine are not very drought tolerant and require careful water management during dry periods. Tall fescue requires frequent watering (1.5 to 2.0 inches per week) during the hottest part of the summer to keep it growing.
First signs of drought
The first sign of drought stress is that your green lawn (Fig. A) will start to turn a purplish/brown color (Figs. B & C). This is called wilting. The leaf blades will appear much thinner when wilted because the leaf blade has culred or folded up to conserve moisture (Fig. B). After a few days of drought stress your lawn will start to turn brown (Fib. D). If drought continues, portions or all of the turf may turn a brown color and enter into drought (summer) dormancy.
Deciding to water or not
•Many turf areas should be allowed to go dormant, especially where supplies or infrastructure is limiting.
•Turfgrasses that are trafficked during drought conditions (golf courses, athletic fields, etc) MUST be irrigated regularly to maintain performance and prevent widespread turf damage.
•Turf areas established this spring or late last fall should be irrigated because they have not developed extensive root systems.
Advice if you choose to water
•Since all turfgrasses perform best on the dry side, water thoroughly to wet the soil to the depth of the deepest root (maybe 2-4“ into the soil) and then don't water again until you see the turf turning a bluish-gray in the heat of the afternoon (the first sign of drought stress).
•Try to expand the number of days between irrigation cycles, you'll likely be surprised on how long the turf can go without signs of drought stress.
•Consider purchasing a rain sensor for your automatic irrigation system to prevent watering during or after rain events. Also use the irrigation budgeting features of your irrigation system.
•Check your irrigation system for improperly aimed sprinklers, non-turning sprinklers, evenness of distribution, etc. This is true for automatic as well as hose-end sprinklers. This will improve the efficiency of irrigation and cut down on water use.
•Aerify regularly in spring or fall (when soil is moist) with hollow tines to improve water penetration into the soil.
•Water between 5:00 and 8:00 am to improve efficiency because of less evaporation and wind distortion. Irrigating early in the morning does not favor disease. The second best time is between 7:00 and 10:00 pm, but this favors diseases.
Advice if you choose not to water
•Stay off the turf! Limit traffic (including mowing) to minimize crushing of the turfgrass leaves and crowns. •Water once every 4 weeks with ¼ to ½ inch of water to keep turf plant crowns hydrated. This amount of water should not green up the turf, but it will increase its long-term survival.
•Avoid the temptation to apply herbicides even though weedy species may become more obvious in a dormant (brown) lawn. Herbicides are ineffective on drought-stressed weeds and can be damaging on drought-stressed turf.
•Professionals might consider applying 0.75 lbs N/1000 ft 2 with a 60-75% slow release N source. This should help to speed recovery when rains resume.
•Turf should recover in 1-2 weeks after significant rainfall returns.
•Aggressive fertilization may be needed after the rains return and turf recovers.
•Overseeding tall fescue lawns may also be necessary this fall after the turf recovers.
Aaron Patton, Arkansas Turfgrass Extension Specialist
Zac Reicher, Indiana Turfgrass Extension Specialist