Soil Acidity and pH

I have several books on flower growing, but none give the type of soils (acid or alkaline) in which all plants thrive best. Can you give me this information? No complete list has ever been worked out. Of the vast number of plants grown, comparatively few show marked preferences for decidedly acid or alkaline soils. The vast majority exhibit a wide tolerance.

What plants grow well on acid soils of fair to good fertility (pH 5.0 to 5.5)? Andromeda, trailing arbutus, azalea, beans, bent grasses, white birch, blackberry, blueberry, buckwheat, camellia, white cedar, cineraria, cowpea, corn, cranberry, cucumber, cyclamen, daffodil, dewberry, endive, ferns, fir, hemlock, huckleberry, hydrangea (blue), lily, lupine, millet, mountain laurel, scrub oak, red oak, oats, orchard grass, orchid, parsley, pea, peanut, pepper, pine, plantain, potato, pumpkin, radish, raspberry, red cedar, red top, rhododendron, rye, skimmia, soybean, spruce, strawberry, sweet potato, tobacco, turnip, hairy vetch, violet, watermelon, wintergreen, wheat, zinnia.

What plants grow better on slightly acid or neutral soils (pH 5.6 to 6.5)? Beans, blackberry, brussels sprouts, buckwheat, carrot, cabbage, crimson clover, corn, cowpea, cucumber, endive, oats, orchard grass, parsley, pea, pepper, pumpkin, radish, red top, rhubarb, rye, soybean, squash, strawberry, sweet potato, tobacco, tomato, turnip, wintergreen, wheat.

What plants do not grow well on strongly acid soils, but prefer slightly acid or slightly alkaline soils (pH 6.5 to 7.0)? Alfalfa, apple, asparagus, aster, avens, baby's breath, barley, balsam, beets, beggar weed, berseem, blue grass, bokhara, broccoli, brome grass, camomile, candytuft, carnation, cauliflower, celery, chard, cherry, chicory, chrysanthemum, alsike clover, hungarian clover, japanese clover, mammoth clover, red clover, white clover, yellow clover, collards, columbine, cosmos, cotton, currant, dahlia, delphinium, eggplant, american elm, everlasting pea, sheep's fescue, tall fescue, flax, foxglove, foxtail, gladiolus, gooseberry, grape, helianthus, hemp, horseradish, hops, hydrangea (pink), iris, kale, kohlrabi, lady's finger, larkspur, leek, lentil, lettuce, american linden, lobelia, mangel wurzels, maple, marigold, meadow grass, meadow oat, mignonette, muskmelon, nasturtium, white oak, onion, pansy, parsnip, peach, pear, peppermint, petunia, phlox, plum, poppy, orange quince, rape, salsify, sorghum, spearmint, speltz, spinach, stock, sunflower, sweet alyssum, sweet pea, sweet vernal, sweet william, timothy, vetch, walnut, watercress, willow, wisteria, witch hazel, woodbine.

What makes the soil acid? Soil acidity is common in many regions where rainfall is sufficient to leach large proportions of calcium and magnesium out of the soil. Decay of organic matter releases carbon dioxide. Combined with soil water, this forms carbonic acid.

Soils also become acid due to the use of acid-forming fertilizers, such as sulfate of ammonia and ammonium phosphates. The following list shows the relative acidifying or alkalizing power of various fertilizing, liming, or acidifying materials, rated in terms of commercial limestone (calcium carbonate) as 1.0:

Dolomitic Limestone - Alkalinizing (1.1)
Hydrated Lime (Calcite) - Alkalinizing (1.4)
Hydrated Lime (Dolomitic) - Alkalinizing (1.7)
Sodium Nitrate - Alkalinizing (0.3)
Calcium Nitrate - Alkalinizing (0.2)
Potassium Nitrate - Alkalinizing (0.2)

Ammonium Nitrate - Acidifying (0.6)
Ammonium Sulfate - Acidifying (1.1)
Monoammonium Phosphate - Acidifying (0.6)
Diammonium Phosphate - Acidifying (1.1)
Urea - Acidifying (0.8)
Sulfur - Acidifying (3.1)
Ferrous Sulfate - Acidifying (0.4)
Aluminum Sulfate - Acidifying (0.5)

Where can soil be sent to have its acidity determined? To your State Agricultural Experiment Station, college or university.

What simple means can be used to detect acid soil? Soil test kits for testing pH are available at most garden shops. They test both alkalinity or acidity. Testing for nutrients is more complicated.

Is moss an indication of acidity? No. Moss grows on either acid or alkaline soil. Usually it means low fertility and high moisture.

Are toadstools an indication of soil acidity? No, they are not.

What will an acid soil produce? Notable among the plants that do best in an acid soil are those of the Ericaceae, which includes such plants as azalea, rhododendron, leucothoe, pieris, mountain laurel, and others.

How can an acid soil be neutralized? An acid soil can be neutralized by adding ground limestone. The amount required can be determined by a soil analysis.

What is "sour" soil? A "sour" soil is a term sometimes used to denote the condition that develops in a poorly drained soil. More often, as the term is used, it is synonymous with an acid soil. If by "sour" soil is meant an acid soil, it can be sweetened by adding agricultural ground limestone or other forms of lime.

What can I do to counteract sour soil in seed boxes? The "sour" soil condition in seed flats can be prevented or corrected by providing sufficient drainage. Separate the boards on the bottom of the flat 1/4-in., or bore a few holes in the bottom. Raise the flats on bricks or wood strips. "Sourness," in these cases, generally does not mean acidity.

How can I improve a dry, acid, heavy clay soil? Incorporate a liberal amount of peat moss, but first mix 10 to 15 lbs. of pulverized limestone with each bale of peat before the latter is worked into the soil. Apply additional limestone to the soil if needed. Always test for pH after soil settles following treatment.

I am making a vegetable garden on a piece of lawn; the soil is very acid. Will it be worth trying? Sine most vegetables will do well on a slightly acid soil, this very acid soil could be changed without undue expense to grow vegetables by adding ground limestone.

What type of fertilizer is used in planting vegetables in acid soil? If the soil is too acid to produce the vegetable crop in mind, apply lime. In addition apply a fertilizer best suited to the particular crop.

My soil is neutral. Is there any chemical I can add to the soil to make it acid? I wish to try acorns from red oaks, and other things. Finely ground sulfur or ammonium sulfate can be used to make the soil more acid. Red oaks, however, will do well on a neutral soil.

Can the soil in a garden in a limestone country be made permanently acid? No. An acid soil made under such conditions can be maintained only by periodic treatment.

What use is sulfur for soil? How do you use it? Sulfur is used to increase the acidity of the soil.

What materials should be used in maintaining an acid soil garden in a limestone country? Acid peat moss or oak leaf mold, flowers or sulfur and ammonium sulfate.

How should acidifying materials be handled in the development and maintenance of an acid soil garden in a limestone country? Make provision for perfect drainage of the area. Incorporate a liberal application of peat moss. Add dusting sulfur in the quantity, and as often, as soil tests (made at least once a year) indicate that it is necessary.

What are the best kinds of leaves for producing an acid condition in the soil? Leaf mold from oak leaves has long been considered the ideal acidifying material for plants requiring an acid soil, such as rhododendrons, azaleas, and mountain laurel. Recent experiments, however, indicate that his assumption is incorrect. Oak leaf compost increased the pH temporarily, but after 45 days the pH value was higher (less acid) than before the application. However, there is no doubt that oak leaf mold is beneficial to the growth of the acid-loving plants. In soils high in humus, acid soil plants can tolerate higher pH readings.

Will you please tell me how to prepare a soil mixture using oak leaf mold for growing blueberries? Dig a hole 3 to 4 ft. wide for each plant; incorporate 3 ins. of leaf mold in the bottom; mix the soil for filling with 1/3 its bulk of leaf mold, and pack tightly around the roots. Keep the surface over the roots mulched heavily with the oak leaf mold, or with sawdust. Use ammonium sulfate to further acidify.