Gypsum May Solve Clay Problems

Is clay or hardpan soil a problem in your garden? Gypsum may be the answer. A three-year program of yearly applications should help improve poor soil. Gypsum is easy to apply and relatively inexpensive.

One of the biggest garden problems is clay or hardpan soil, which may be poorly drained, soggy and compacted. In a new garden, work in organic humus to break up poor soil. Bark, sawdust, manure, compost, peat moss and soil mulches and conditioners may be used. If bark or sawdust is used, it will leach nitrogen from the soil as it decomposes, so nitrogen must be added.

But in an established garden it would take too much work and time to dig, replant and recondition the soil. Here's where gypsum may be the answer. It can be applied on the surface in a vegetable garden, flower beds or lawn. It does not have to be cultivated into the soil.

Gypsum penetrates the millions of clay particles in heavy or hardpan soils and loosen the structure. This creates air and moisture spaces which loosen and break up the soil. The only problem is that it takes yearly applications for about three years.

Gypsum contains no major plant nutrients, so it is necessary to fertilize regularly. Add organic humus in new areas as you plant. Gypsum does contain calcium and sulfur, which aid plant growth.

Gypsum is easy to apply. Spread it on the lawn with a lawn fertilizer spreader at 50 pounds per thousand square feet. The granular grade is the best and easiest to apply in home gardens.

A single application each year is sufficient. It can be spread any time of year. Water it in right away in order to get it working. Gypsum is neutral and non-toxic to humans and animals and does not burn.

When preparing new soil for flowers, shrubs, vegetables or a lawn, mix 20 to 30 pounds of gypsum per 100 square feet of heavy soil and water well.

If you are applying gypsum around established plantings, use 50 pounds per thousand square feet. Under these circumstances, gypsum can be spread or broadcast over the beds. A single application should be made once a year over three years. There is no need to mix it into the soil; simply water it in.

Since gypsum is neutral and does not change the soil pH, you can use it where acid-loving plants such as rhododendrons, azaleas and camellias grow; they need a little calcium, too. Apply gypsum as directed on the label.

Your garden outlet may not stock gypsum because it does not get enough calls for it. They can special-order it for you. It is usually available in 80-pound bags and occasionally in 50-pound bags. Ask for a price quote before you buy.

Gardening by Ed Hume appears Thursday and Friday in the Scene section and Sunday in the Home/Real Estate section of The Times.