The number of vegetable gardeners rose tremendously last summer, but poor soil conditions resulted in disappointments for many. Soil that is too sandy, too clayey, too dry, too wet or too infertile can be corrected to a considerable degree: By proper management, soil can be improved year after year.

The best thing to do is to work organic matter, lime and fertilizer into the soil. First have it tested to find out how much lime and fertilizer to apply -- your county extension agent can suggest how to take the soil samples and where to send them.

Organic matter helps unite the fine particles of clay soil into larger ones and increases the size of channels through the soil. Lime also helps to draw many of the smallest-sized particles together into larger ones. The space between these larger particles is enough to permit more rapid air and water movement.

In sandy soils, the soil particles are much larger, the pore spaces are large, too much of the water runs right through, and they dry rapidly. Nutrients leach away in the soil water.

Organic matter increases the water-holding capacity of sandy soils. After organic matter becomes partially decomposed, it is called humus. Humus binds the particles of sandy soils together, reducing the size of pore spaces, and helps prevent nutrients from leaching out.

Good organic matter includes compost, peat moss, barnyard manure, sawdust and similar materials. Peat is very effective because it lasts longer in the soil. Compost is good, and you can make it yourself with leaves that fall in autumn.

Spread a three-inch layer of whatever organic matter you choose and some lime and fertilizer over the ground. Rototill or spade it into the top six to nine inches. The soil test will tell how much to use.

Be sure the organic matter is mixed thoroughly with the soil. Research has shown that a mat of organic matter can block the movement of air and water between the surface and subsoil.

In many gardens it may be helpful to improve the subsoil. This can be done by double spading.

The better the root system of a plant, the better it can withstand drought. Layers of compacted soil 10 inches below the surface may check root growth.

Research has shown that it is the inability of plant roots to penetrate tightly packed soil that restricts their growth, rather than a deficiency of air or moisture. Scientists thought it was the other way around until tests showed that root growth was hindered only when layers of soil offered too much resistance to root penetration.

The purpose of double spading is to work organic matter into the subsoil, but it must be done without mixing very much of the subsoil with the surface soil, otherwise the texture of the surface soil will be adversely affected.

Digging deeply merely to loosen the soil does not accomplish anything, because after a couple of rains the soil settles back to the former condition.

Each layer should be spaded separately and not mixed with the other.

Start spading at one end of the garden by removing a three-foot strip of surface soil to a depth of nine inches. Pile it to one side. Then spade the subsoil nine to 12 inches deep and mix in organic matter, lime and fertilizer.

Next remove another three-foot strip of surface soil and place it on top of the subsoil that has just been worked. Mix organic matter, lime and fertilizer into it.

Then the newly uncovered subsoil is spaded as before, and so on across the entire plot.

The surface soil removed from the first strip is carried over to cover the spaded subsoil in the last strip.

If the substratum below the subsoil is badly compacted, it may be desirable to do three layers of spading.

If the top layer has only three or four inches of topsoil, the first layer should be only that deep, to avoid mixing good soil with subsoil.