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Monday, September 19, 2011

Lawns Brown Spots Can Be Dogs and Poor Sprinkler Coverage

Dog urine damage leaves a dark green edge
around the damaged brown spot caused by the urine

Most likely there is a popup sprinkler in the center of that
green patch surrounded by bare soil. It is most likely
a two inch popup when a four inch is needed in tall fescue
Q. My lawn was sodded with tall fescue lawn grass a few years back and this past fall noticed I still have two problems. The pictures attached. The first are five to ten inch circles which are brown in the center with very dark green grass around it. The second are areas around the edge where there is a patch of dark green grass and then 10-15 inches of bare ground around it. I am really hoping you can provide an explanation and solution to resolve these.

A. The third picture, brown ten inch circles with dark green on the outside, looks like damage from a urinating dog. Urine results in a small round brown area where the grass is darker green around the dead spot. Readers can see these pictures by following my blog at http://www.xtremehorticulture.blogspot.com/

Popup sprinklers need clearance over the grass
if they are going to cover the lawn area evenly
The urine is too high in salts (urea, a salt high in nitrogen) and burns the immediate area around where it is applied. As the urea moves into the surrounding soil it becomes more dilute, reducing the burning, and then acts like a fertilizer high in nitrogen. Nitrogen fertilizers turn grass a dark green.

The other picture with 10 to 15 inches of bare ground around a green area, looks like the sprinkler head is in the center of that small green area next to the curb. If that is the case, I am guessing the popup is not “popping” high enough. Make sure it pops up all the way and is not getting blocked. Make sure your irrigation sprinklers are 4 inch and not 2 inch popups. Two inch popups do not pop up high enough to spray evenly above the top of a grass mowed at two inches in height. The grass height interferes with the water spray.

Pressure regulator
Also check your water pressure. It should be in the 40 to 50 psi range for most popups. If it is a lot higher than this, then your sprinklers are probably “fogging” and not delivering the right sized droplets to get even coverage over the lawn. Install a pressure regulator to drop the water pressure in the appropriate range recommended by the irrigation manufacturer for the sprinklers and nozzles.

Your tall fescue does not look very luxurious in general. It would improve from some good lawn management practices. Tall fescue is best if mowed no shorter than 1½ inch, and 2 inches is even better. Use a mulching mower and return the clippings to the lawn; don’t bag them and leave them for the garbage.

Roots of turfgrass grow easily into holes punched in
the lawn by an aerifier
Try aerating the lawn any time of the year and follow this with an application of a good quality lawn fertilizer. If you are returning the clippings to the lawn then fertilize Labor Day, Memorial Day and 4th of July. Be sure you also make an application around Thanksgiving to keep your lawn dark green through the winter months.

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