Soil Requirements For A Successful Organic Garden

6. Soil Requirements For A Successful Organic Garden

6.1 Nitrogen

A balanced organic compost should contain nitrogen, phosphorus, and potash (potassium). As a rule, calcium, sulfur and magnesium, as well as trace elements like zinc, boron, manganese, molybdenum, copper, and chlorine (and many other trace minerals, known and unknown) will be available in your soil for plant nutrition, if you are constantly adding a variety of organic materials to your soil.

Nitrogen is important in the production of protein; leafy, green vegetables, especially, need adequate supplies of nitrogen. Too little nitrogen will be evidenced by pale green leaves, progressing to yellowing and dropping of older leaves, and stunting of growth. Too much nitrogen will produce an excess of greenery and little or no fruiting, and the plants may be spindly and weak, and susceptible to disease.

Nitrogen is supplied by blood meal, castor pomace, soybean meal, cottonseed meal, fish meal, or feathers, or bone meal, or straw, alfalfa hay, or manure. If you use bloodmeal or manure, use it very sparingly.

Nitrogen is also supplied to the soil by growing legumes, which capture nitrogen from the air, enriching the soil in which they grown, as well as adjoining areas. (The air is almost 80% nitrogen.) Earthworms will also help supply nitrogen to the soil. See the article “Nitrogen Fixation” in this lesson.

Planet Natural carries “Alaska Fish Emulsion,” an excellent source of nitrogen. Do not add concentrated nitrogen to plants when fruits are ripening. To encourage ripening, add either a balanced compost, or phosphorus or potash.

6.2 Alfalfa: The Best Source of Nitrogen (Plus Growth Stimulation)

In 1975, Dr. Stanley K. Ries, a horticulturist at Michigan State University, found that alfalfa treated plots produced increases far above what the nitrogen in the alfalfa could account for.

In the laboratory, they isolated the active agent—triacontanol, a fatty acid alcohol which occurs naturally in the plant’s leaves. Triacontanol is not a fertilizer, but a growth stimulating substance.

The Rodale Organic Gardening Research Center tested the use of “greenchop” alfalfa in extremely small counts. Both Ries and the Rodale Center reported (The Best Gardening Ideas for the ’80s) that the less alfalfa they applied, the better the yield—but, with no alfalfa, they got the lowest yield. The amount used which provided the best yield works out to about one cup of fresh chopped alfalfa for 100 square feet of garden. Simply spread it over the plot, work it in, and plant your vegetable seeds. Use mulch as usual.

The Rodale book says that the methods and rates of application are still in the experimental stage.

The main advantage of alfalfa is as a nitrogen-fixing legume. Fresh-cut alfalfa contains more nitrogen than any manure. Use alfalfa in the garden as a soil-enricher to be rotated through the garden, or as a patch to produce a high-nitrogen material for mulch.

6.3 Phosphorus

Phosphorus is necessary to the production of plant sugars. The symptoms of phosphorus deficiency are similar to those of nitrogen deficiency, but the leaves may be dull green with purple tints. Some phosphorus sources are rock phosphate, bone meal, granite dust, natural limestone, gypsum, and fish scraps.

6.4 Potassium (Potash)

Potassium (potash) is essential to the life processes of plants. It is helpful in hastening development and maturity. Symptoms of potassium deficiency are slow growth and leaves with mottled yellow tips and edges, and scorched-appearing edges on older leaves. Seaweed or seaweed spray provides generous amounts of potassium. Some other potash sources are wood ashes, granite dust, potash rock, citrus rinds, kelp, greensand, and bone meal.

6.5 Calcium

Enough calcium will usually be present in the soil, but bone meal will supply some additional calcium especially needed for grapes, celery, and sometimes tomatoes.

6.6 Sulfur

Like nitrogen, sulfur is a protein provider, and will usually be present in adequate amounts in the organic garden.

6.7 Magnesium

Magnesium is a vital nutrient, important in the leaves of living plants. It is necessary for the process of photo-synthesis—through which plants manufacture their own food and fuel—utilizing energy from the sun, carbon dioxide from the air, and water and nutrients from the soil. Usually there is enough magnesium present in the soil of an organic garden. However, occasionally, an acid-loving plant will indicate a deficiency, evidenced by yellowing leaves, which may be corrected by using dolomitic limestone or raw phosphate rock.

6.8 Feed the Soil Which Feeds the Plant

See the list of compost materials, with percentages of nutrients, in the supplementary section of this lesson.

Organic compost—and the various nutrients of organic origin which may be added to the soil—do not overwhelm plants with a tremendous amount of one particular element, as can happen with chemicals. The chemicals attempt to feed the plant, whereas the organic fertilizers feed the soil which nourishes the plants.

This more natural way produces the best food, and makes it unnecessary to be preoccupied with exact ratios of various elements, such as the 6-6-6 chemical fertilizers (6% nitrogen, 6% phosphorus, 6% potash). Generally speaking, these nutrients from organic sources should be added in approximately equal amounts, but be particularly careful not to use too much nitrogen from animal sources (such as manure, blood meal, or dried blood). Your soil will make the best use of the organic fertilizers for the nutrition of your plants.

Sand Mueller, instructor in horticulture at Triton College in suburban Chicago, says that seven years ago he was operating a conventional greenhouse in New Mexico. He visited greenhouses all over the Southwest, all of which used agricultural chemicals. All of them had insect problems, and all of them used powerful poisons.

Mueller had read claims by organic gardeners to the effect that their healthy plants had little or no insect problems. He says, “I believed these assertions were preposterous, as did every horticulturist I knew.”

But he eventually decided to try the compost idea, and his insect and disease problems rapidly began to disappear. After he started to compost, he learned the law of survival of the fittest in the plant kingdom.

Mueller tells how, in 1936, a British agricultural scientist, Sir Albert Howard, grew half a field of alfalfa with artificial fertilizer and half with compost. His oxen devoured the compost-grown alfalfa first. Given a choice, animals will always select the organic food.

After building up the health of the oxen with the organic feeding, Howard deliberately exposed them to the hoof and mouth disease, but none of the oxen became ill. Dr. William Albrecht, professor of soil science at the University of Missouri, corroborated Howard’s findings.

In 1976, Mueller offered his flock of chickens the choice of commercial feed or grains he had grown in composted soil. He says, “With a cacophony of cackling and scratching, my hens asserted the truth of Howard’s claim.”

Mueller says, “The horticulture establishment has only one response to compost and that is ridicule. It is the response of ignorance. I do not believe that there exists anyone in the field of agriculture who has tried organic agriculture who now advocates chemical agriculture.”