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Saturday, August 20, 2016

Bermudagrass Lawn Change of Color May Be Drought

Q. We have lived in the same house in Las Vegas for the last 42 years and every June my lawn has the same problem. The lawn is a mix of common and hybrid Bermudagrass. First the grass turns grayish (in patches) and then it turns brown. It slowly comes back by September. I water according to local recommendations, use Scott's Turf builder 3 to 4 times a year and use Ortho Bug-B-Gone insect granules twice a year.
A. If this were tall fescue I might be tempted to say this is a disease problem. However, since it is a mixture of Bermudagrasses I think this is an irrigation problem. This will be particularly true if these problem areas are in the same locations every year.
Turfgrass or lawns will turn a smoky or grayish green when they are not getting enough water. This is because the leaf blade either folds in half or roles depending on the grass. This creates a different color; smoky or grayish green
            Bermudagrass in our climate doesn’t develop many insect or disease problems.
            The success of lawns in our desert climate is directly tied to the quality of an irrigation system. In technical terms we say the irrigation system should provide head to head coverage; water from a sprinkler head should be thrown far enough to reach the head to its right and it’s left. If we don’t provide this kind of uniformity in the design and installation of an irrigation system it can result in brown patches that don’t receive enough water.
A close-up of the grayish green color where the lawn is not getting enough water
            The water pressure in the sprinkler system should fall within a range recommended by the sprinkler manufacturer. If the water pressure is too high or too low it will affect the distribution of water and create browning of the lawn in the same areas year after year. Otherwise, there are sprinklers now that will lower the water pressure before the water is applied to the lawn.
Another indicator of drought or lack of water in a lawn are footprints. If you walk across grass that needs water, look behind you. If your footprints remain in the grass does not spring back quickly, the grass needs water.
            You can correct this problem in the short run by increasing the number of minutes that you apply water. This delivers more water to the dry areas. Unfortunately, it also delivers more water to the wet areas resulting in overwatering of the green areas.
            It is also a good idea to punch holes in the lawn with an aerating machine in the spring, particularly in the brown areas. This helps water to move into the soil and not run off into low spots if there are any.
            Bermudagrass is notorious for building up “thatch”. Thatch is a buildup of old grass stems and debris under the surface of the lawn but on top of the soil. Years ago this thatch was burned off of the lawn with fire. We can’t do that anymore. We must do it mechanically now.
A core aerifier for lawns pulls plugs or cores out of the lawn that are about 4 inches deep. This type of verification provides better drainage and water penetration for lawns suffering from drought
            It is important to dethatch Bermudagrass each year. This is usually done in the fall when overseeding it with a cool season grass like ryegrass to maintain a green winter lawn. If the lawn is not overseeded in the fall then thatch can be a huge problem in Bermudagrass.
D thatching machines, sometimes called vertical mowers, pull debris from a lawn which allows water to better penetrate the soil and reduces runoff.
            Making changes to the irrigation system will correct some of this problem and reduce the amount of water needed to keep the lawn green. Increasing the number of minutes you apply water during the heat of the summer should solve this problem in the short run.
            But I would combine this with lawn aerification every three or four years and dethatching every year to improve the amount of water entering the soil in the dry areas.

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