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Combating salt

April 22, 2002|By Keith S. Mayberry, Imperial County-University of California Cooperative Extension adviser

A reader in Imperial wrote "I got alkali in my yard. I tried to poison it with manure but it won't die. What can I use to kill it?"

Can you imagine someone trying to poison a Rolaid tablet? Alkali is not alive and is often defined as any of various soluble mineral salts found in natural water and arid soils.

Salt comes dissolved in Colorado River water. When we water the yard we also are applying salt. An average 30-foot-by-30-foot yard could receive as much as 250 pounds of salt per year. If the salt is allowed to accumulate, the lawn will eventually start to show brown patches, then the grass will die in ever-larger spots. Sometimes there will be a white or a wet-looking brown crust depending upon the kind of salt that is dominant.

The water is used by plants and is evaporated from the soil surface. The salt starts to build if there is insufficient leaching.

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So what is the solution to salt?

You need to irrigate enough to wash the salt out of the root zone. This process involves adding enough water for the lawn, plus roughly 15 percent more. Typically you need to water once every 10 days in the winter and up to two to three times per week in the summer. The irrigation frequency depends upon many factors, especially the kind of watering system you have. Is it flood irrigation? Built-in sprinklers? Hose and sprinkler? Each type delivers a different amount of water.

To leach you need to apply what is known as "deep irrigations." For me, this is running a sprinkler in one location for an hour or more. If the soil starts to have excess runoff, then move the sprinkler. I use the timer on the kitchen stove to remind me to make changes.

Some homeowners run their time-clocked sprinkler systems for 15-20 minutes a day. This is not recommended. Why? Too little water is applied at any given time for good leaching. It is better to run the sprinklers for an hour every other day and have some leaching.

Sometimes lawns have steep slopes. Running the built-in sprinklers for more than 20 minutes results in runoff onto the sidewalk and street. If that is the case, run the sprinklers for 20 minutes, change the sprinkler set to another location and later move it back to the site for an additional application of water in the same day! This practice will allow for some leaching of salt.

Bermuda grass has more salt tolerance than does St. Augustine grass. If you have a salty soil then go with common Bermuda grass.

If there are large areas to be leached — as with a new non-landscaped home or annual vegetable garden — there are a few techniques that will help:

Apply a 2- to 3-inch layer of organic mulch or steer manure, then spade or rototill the soil as deep as you can. With a new home it may pay to have the soil ripped with a tractor-mounted chisel.

If you are building a home, NEVER let the contractor compact your whole yard. You'll find it nearly impossible to grow healthy trees and shrubs after the soil has been so mistreated. Use one of the following methods to wash out the salt.

>> Method 1 — ponding:

Build a 6-inch dike around the area and fill the basin with water. When the water disappears, refill it. Five or six fills should be enough. When finished, scoop up the soil forming the dike and discard it.

>> Method 2 — ridging.

Make 6-inch beds that are 6 inches apart, similar to the corrugation on an old washboard. Run the water down the valleys and the water will move to the tops of the hills, carrying the salt to the peaks. Skim off soil in the salty peaks and throw it away. Mix the rest of the soil and repeat this process. This method works well in areas that have dense clay soils such as those found in Calexico, Imperial and southwestern El Centro.

>> Method 3 — misting.

After the soil has been worked up well by spading or rototilling, lay a long misting-type soaker hose across the area. The misting hose is a type of hose that look like someone just went wild punching needle holes into it. Stake the hose down solid with hoops made from old wire coat hangers.

Let the water spray upward (not downward). Water applied slowly is efficient in removing salt without causing crusting or sealing the soil surface.

Don't become too impatient with salinity management. It is not unusual to take a year or more to correct a bad situation.

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