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Monday, April 18, 2016

How to Judge How Much to Water a Lawn

Q. I am responsible for maintaining a bermudagrass lawn at a church where the foot traffic is pretty high. The lawn gets 25 minutes of water three days a week, all in one watering because the lawn is very flat. But it still looks thin in spots. Can you tell me if this is the right amount of water?

A. Water is tough to measure in minutes. It is usually measured in gallons or inches of applied water. Right now, March and April, lawns need about 1/4 inch of water per day. After four days, apply 1 inch of water.
This was how we measured how evenly water was applied to turfgrass on a golf course. There are hundreds of quart plastic containers placed on this grass. You can do the same on a much smaller scale with your home lawn. But you must have several cups to be accurate.

To translate 1 inch of water to minutes put several cans out in random places, measure how much water is applied in five minutes and then in 10 minutes. Translate the lowest amount caught in cans into minutes.
Another method is to water the lawn for 15 minutes. Take a long pointy device, like a long screwdriver or piece of 3/8 inch rebar, and shove it into the lawn in five different places. Measure how deep the water has penetrated. It gets harder to push when it is dry and pushes easily when it is wet.
A long screwdriver can be substituted for that piece of rebar

Run the irrigation long enough for water to penetrate to one foot. When the water penetrates to this depth, then this is the number of minutes to run the sprinklers. These minutes aren’t changed much throughout the year.
What is changed is how OFTEN the sprinklers come on. Three times a week seems quite often for bermudagrass this time of year. It should be about every three or four days between irrigations when watering a foot deep.
Applying enough water helps fill in bare spots. But what really causes bare spots to fill in quickly is enough water PLUS a nitrogen fertilizer. Apply ammonium sulfate, 21-0-0, to the lawn every 8 weeks. Use 3 to five pounds of this fertilizer for each 1000 square feet of lawn.

Apply it with a handheld spreader over the entire lawn and water it in. Apply it more heavily in bare areas. Mow it somewhere between 1/2 and 1 inch in height. Taller grass is more wear resistant.

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