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ISSUE 15  August 13, 1998



    We asked (some even prayed!) for drier weather, and now we have it. Earlier in the season we were wishing we had sophisticated drainage systems rather than garden hoses or automatic irrigation systems. Well, when the neighborhood kids can bounce their basketballs as easily on the lawn as they can on a concrete drive, it is time to consider watering - for the lawn and the trees and shrubs. The questions is, how much?

    Turfgrass species used in our region are usually fairly drought tolerant. They can go 2 to 3 weeks without supplemental irrigation before getting into dire straights. Their reaction to this water shortage is dormancy. At that point, the homeowner needs to make a decision as to whether or not to water to regreen the lawn, or simply provide enough water to keep it in dormancy and alive. Making the first commitment should be a permanent one - greening the grass up, then letting it lapse back into dormancy will exhaust the turfgrass plants of their carbohydrate reserves, weakening the turf, and making it more vulnerable to weed invasion, diseases, and insect damage. It should also be noted that the turfgrass will be more vulnerable to damage from physical activity as well.

    To keep the turfgrass green, or to pull it irrevocably out of summer dormancy, about 1 inches of water needs to be applied weekly during the non-rainy period. On a 10,000 square foot lawn, this amounts to about 9,600 gallons of water each week, or 41,280 gallons per month. Keep in mind this is just for the landscape - not washing the car, clothes, dishes, or teens bathing!

    To put a cost to this, figure about $3.30 for each 1,000 gallons after the initial 2,000 gallons used in a month. This makes the cost for 39,000 gallons of water to be $128.70, plus the base charges for the water meter.

    To keep the lawn alive and dormant, but not green, requires about 1/4 to 1/3 inches of water/week. This greatly reduces the demand for water to a mere 160 to 213 gallons/1000 square feet of turfgrass, or just 6,880 gallons in a dry month like August. Likewise, the dollar cost is diminished to just an additional $13.20! Is green worth that much? You decide.

    Personally, I am watering my front lawn for two purposes. To keep the Touchdown bluegrass looking fairly green, and to keep my beautiful birch healthy and vigorous. If that tree should become drought stressed, it is then a more vulnerable target for opportunistic insects like the bronze birch borer, and I have then lost a major property asset! Turfgrass is much easier to replace than a beautiful mature tree.

Ron Smith
NDSU Extension Horticulturist and Turfgrass Specialist

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