A VEGETABLE garden needs special conservation measures because the soil must be laid bare and cultivated each year. Particularly, it needs the application of organic matter. Soils can be made much more productive by mixing organic matter and fertilizer with them. Compost is one of the best organic materials to use.

Composting is the process by which wstes from plants and other organic materials are reconverted into a fresh organic matter necessary for the continuation of life. It is nature's way of recycling.

Compost is inexpensive, you can make it yourself. Every fall tons of tree leaves go to waste. The leaves were burned until it became illegal to do so. These leaves can be used to make compost.

As the leaves drop, rake them up and put them in an enclosure that is surrounded by women wire or some material that will hold them in place. Lawn clippings, vegetable and fruit refuse and other waste materials are also suitable. A rectangular area of 80 square feet (8-by-10-feet) may be about right.

Put a layer of loose leaves two feet deep on the ground. Sprinkle 10 pounds of 5-10-10 fertilizer over the leaves. On top of the leaves put a two-inch layer of soil (this is desirable but not a must).

Add another layer of loose leaves, two feet deep, then tramp thoroughly. Add 10 pounds of 5-10-10 as before. Wet thoroughly. Add another two-inch layer of soil (it isn't a must).

Then add the last layer of leaves, two feet deep. Sprinkle with 10 pounds of 5-10-10 and drench with water. Add two inches of soil if it is available.

In lagte winter or early spring turn the compost pile two or three times to speed decomposition.

Put the compost pile on top of the ground rather then in a pit or trench. Water drainage might be poor in the pit of trench, which would slow down decay and possibly create a bad smell.

Decay is brought about by soil microbes. Their food is nitrogen. That is why the fertilizer is applied. It also provides phosphorus and potash.

Air should be able to penetrate the entire compost heap to allow the microbes to finish the compost in a minimum of time. The compost heaps should be built no more than six-feet high so air can penetrate to the bottom of the pile. Excessive moisture reduces aeration by filling air spaces in the heap and by increasing compaction. Only partial decomposition takes place when aeration is insufficient. Turning the heap over will take care of poor aeration.

Dead leaves are sometimes hard to wet. It can be done best by applying the water in a fine spray. If necessary, water should be applied on two or three successive days at the start of the composting period.

Rainfall may increse moisture in the heap. If the moisture becomes excessive and the heap begins to smell, loosen the pile by turning it.

The temperature inside the heap may rise to 140 to 170 degrees F. for two or three weeks. It greatly shortens the time required for decay of the plant material and also kills desease-causing organisms, insects and weed seeds except in the outer parts and the bottom of the heap.

Q. Can you tell me how to grow leeks? I tasted some and they were delicious.

A. Leeks are a valuable addition to the winter garden since they can be left in the ground and harvested fresh during the winter and early spring in areas where temperatures do not go much below zero. The edible part of the leek is the stem, which is blanched by covering it with soil to keep it white and tender. They are particularly good in soups and stews. Plant the seed indoors in March. In April plant the young plants outdoors three or four inches deep and four to six inches apart. To prevent rot, fill the hole around them gradually. Eventually plants should be hilled to provide additionally blanching. You can start harvesting them in midsummer. Plants continue to increase in size until late fall.

Q. Our Big Boy tomatoes are ripening and some of them have splits on the bottom end. What causes it?

A. The fleshy part of the tomato grows and splits the skin when it does not expand. The fruit will not keep very long but otherwise is all right.

Q. Is it necessary to sucker sweet corn?

A. Researchers have found that generally nothing is gained by suckering sweet corn, assuming that it is not planted too close together.

Q. How can I tell when a watermelon is ripe?

A. A good sign of ripeness is the change from white to yellowish color on the underside of the melon. If you are not sure whether it is ready to pick, cut a plug out of it. Be careful not to bruise the skin of the melon when you harvest and take it out of the field.

Q. My neighbor picks his tomatoes when they turn pink and takes them indoors to ripen. He says he gets better results that way. Do you recommend it?

A. To get the best flavor and color, tomatores should be harvested after they are fully vine-ripened. That is one of the main reasons for growing them, to get the fresh flavor you cannot find in those sold in most markets.