Fixing a failed yard

An acquaintance (I'll call him Fred) recently told me about his relatively new lawn. Fred was pretty upset with its condition. For more than two years, he had fertilized, limed, seeded, mowed, aerated and watered faithfully. Yet, in spite of all his efforts, the lawn looked patchy, was continually invaded by weeds and never really "greened up" like it should.

Fred had managed lawns in other locations that thrived under his care. They were lawns of which he could be proud. But this lawn was giving him fits. What could he do? I asked Fred to push a long screwdriver down into the soil, as far as he could, in an area where the lawn looked green and lush, and then do the same thing where the lawn was patchy and off color. Then report back to me.

Within a day Fred called me and said that where the lawn was good and green, the screwdriver was easily pushed into the soil. Where the lawn was patchy and off color, he couldn't push hard enough for the screwdriver to penetrate the soil.

Fred's "new lawn" had been established over subsoil. During the house-building process, the topsoil had either been removed or pushed to the side. The subsoil that was left consisted primarily of clay.

Clay is a concentration of fine soil particles that stack together like bricks stacked in a wall of a house. In addition, these fine particles are bonded together by electric charges on their surfaces. The electronic charges (bonds) act as a mortar between individual clay particles and hold the particles together, just as a mortar holds the bricks together in a brick wall.

With this picture in mind, you can see why Fred was having so much trouble growing a nice-looking lawn on the subsoil that was left after construction. So what is Fred to do? I told Fred to aerate his lawn with a core aerifier. This machine pulls up plugs of soil and deposits them on the surface of the lawn. If you play golf, you have probably seen this done at one time or another on a golf green.

After aerification, Fred then needed to apply palletized gypsum over his entire lawn. I suggested he use a rate of 40 to 80 pounds of gypsum per 1,000 square feet. In addition, I told him to perform this same practice every spring and fall for two or three years.

What is gypsum, and what does it do? Gypsum is CaSO4, more commonly known as sheet rock. Purchase it in the pelletized form and spread it over your lawn as you would a fertilizer. Gypsum has the ability to break some of the electric charges (bonds) between individual clay particles in the soil. The net result is that clay becomes more arable.

To picture the change in the soil, think again of a brick wall standing along a building. Each brick in mortared into place, and there is no air space between bricks. Nothing can penetrate the brick wall.

Now picture the building after being razed. There is a pile of rubble. You see clusters of bricks, two or three bricks still mortared tightly together. But between clusters, you find a lot of air space.

So it is with clay in a lawn after treatment with gypsum. You find clusters of clay particles bonded together, but you also find a lot of air space between clusters. Now roots can penetrate through the air spaces between clusters of clay particles. Your soil now has spaces within which rain can penetrate and be stored for use in times of drought. Your clay soil will break up between your fingers, instead of forming a clay mud ball. The gypsum has altered the physical properties of the clay soil.

Treating your lawn with gypsum will not change the soil pH. Therefore the nutrients that you add when fertilizing will be just as available to grass plants as they were before adding gypsum.

Although I have talked about applying gypsum to your lawn, the same reasoning and application rates apply to your vegetable garden, landscape bed or flower garden. By changing the physical properties of the soil in these gardens with gypsum, you can watch your plants flourish and thrive instead of just survive.

Send your gardening and landscape questions to Paul Schnare at P.O. Box 699; Cape Girardeau, Mo. 63702-0699 or by e-mail to news@semissourian.com.