Even the agronomists favor Tonge's backyard loam

I'd like to tell you something about my backyard sand. Over the years it has turned into soil -- good garden loam, capable of producing good garden-fresh vegetables.

Just by looking at it -- the crumbly nature of the soil, the presence of countless earthworms, and, of course, the general well-being of the growing vegetables -- testifies adequately to the effectiveness of a soil-building program involving no additives beyond home-made compost and shredded leaves.

But this year I have additional proof: I had the University of Massachusetts Cooperative Extension Service do a soil test and the results were more than satisfactory.

In filling out the questionnaire, I had stated that my "yield goal" for the garden was "high." To get that high yield, the extension service suggested I need add only 25 pounds of a general-purpose 5-10-10 fertilizer over the roughly 1,000 square feet of garden area. That's half the normally recommend application for standard garden soil.

The soil needed no lime, either for calcium content or to lower the acidity. In fact, the soil tested out at 6.8 on the pH (acid-alkaline) scale, or about perfect for vegetables.

All the major nutritients (nitrogen, phosphorus, and potassium) are available in adequate or better quantities. For instance, the detailed analysis shows more than enough slow-release nitrogen (nitrogen that is released as bacterial action transforms it into readily assimilated nitrates). Ammonium ion, as it is called, tests out at 48 parts per million in my garden. According to the extension service, 24 ppm is considered high.

Phosphorus, too, is higher than usual. Only the potassium is somewhat less than high, but still adequate -- 147 ppm on a scale that runs from a low of 50 to a high of 200.

Trace elements also are available in adequate quantities. Even more important in city and suburban communities is the almost total absence of toxic heavy metals in the soil. The lead content (1.7 ppm) could be increased tenfold and still be below acceptable levels.

Let there be no illusions, however. My garden's soil still drains to readily to be perfect (in times of dry weather I have to water more frequently than those with more substantial soils). But the transformation from the sort of material that is a drainage engineer's delight to good crop- producing loam is, nevertheless, remarkable. It has proved, as nothing else has, the effectiveness of the organic approach.

Leaves, which I gather from the neighborhood streets each fall, and compost, which I make on a continuing basis from kitchen waste, weeds, and spent vegetation from the garden, are basic to this soil-building, vegetable-feeding program. Occasionally in the past I have been able to get hold of some chicken and rabbit manures, but not on any regular basis. I certainly would use them were they available and not too expensive.

Originally, I spread leaves over the garden and tilled them into the soil early in the spring. That still is a great way to get organic matter into the soil. I know of many gardeners who till about a 12-inch layer of leaves into the soil once a year and that's all they do. They have great soil and well-stocked larders.

Now my approach has changed somewhat. An almost- permanent mulch of shredded leaves, occasionally augmented by shredded newspapers, is the key to soft, friable soil at all times. I no longer till and do very little digging in the garden. It simply isn't necessary. Another plus for muclhing: weeds are few and far between.

Each fall I cover the entire garden with between four and six inches of shredded leaves. In the spring this is raked back a week before planting to let the sun get in and warm the soil. A trowelful of finished compost is placed in the planting hole of individual plants, such as cabbage or lettuce. Tomatoes or hills or cukes or squash get a spadeful if it is available.

Compost is spread evenly over the soil and raked in before sowing closely spaced vegetables. If my supply of compost is limited, I reduce the quantity given to each plant but make up the difference by including a light dusting of organic fertilizer. My preference is for a brand that includes micro-organisms as well as the basic nutrients.

Once the plants are up and growing strongly, the mulch goes back on, covering the soil completely to the stems of the plants. As the mulch decomposes under the determined onslaught of earthworms and other soil organisms, it continues to feed the vegetables and improve soil texture. The moment there is any sign of bare soil, more mulch is added.

In a way it's a never-ending process. But then, the results make it all worth while.