A good soil test is the surest way to determine the pH of your soil. A simple test for pH you can do yourself is with blue litmus paper, available from drug stores. Blue litmus turns pink when brought into contact with an acid (even a weak acid like vinegar) and turns back to blue if dipped in lime water.
In years past, a gardener or farmer tasted his soil. If it tasted sour, he knew that it wasn’t good for raising crops. The same thing went for a bitter taste. But if it tasted sweet, he knew that he could expect high yields. He may not have known it, but the soil that tasted sour was too acid to raise good general crops, and the soil that tasted bitter was too alkaline to produce the yields he wanted.
Pull another piece of the paper out in about five minutes. If pink, the soil needs lime, but not as much as when the color changes right away. If after 15 minutes the blue paper shows little or no change to pink, your soil probably doesn’t need lime.
Incorporating good compost helps correct an adverse soil pH to the range wherein most common plants thrive. Even where the pH of a soil is less than optimum for the plants being raised, plants will commonly thrive if there is sufficient organic matter present.
Alkaline soils are most characteristic of salt marshes, the alkali deserts of the West, and some limestone areas. In humid regions soil under cultivation tends to become increasingly acid. This is because soil water dissolves the more alkaline substances like calcium, sodium, magnesium, and potassium faster than acidic materials like carbon. Thus the alkali leach out sooner than the acids.
Their activities are much the same in soil. They attack the roots, stems, straws, and leaves of dead plants sheet composted or plowed into the soil, converting them rapidly and efficiently into a dark brown mass very much like peat (their work is the first step in the formation of peat or brown coal). They secrete digestive enzymes that decompose the three most complex and abundant organic compounds in vegetable matter: protein, starch and cellulose. This is a humidification process resulting in the formation of black coloring substances and the synthesis, or building up, of cell matter into soil organic matter. When large numbers of actinomycetes are at work, a musty, earthy odor rises like a rotting log in the woods or a damp haycock out in the field.
Deficiency of calcium and magnesium is a third possibility. The best explanation may be that in acid soils, chemical reaction can lock up major nutrients, especially phosphorus, making them unavailable to plants. Heavy use of inorganic, high-analysis fertilizers causes soil to become more acid, as does heavy use of sulfur-containing fungicides. Organic gardeners don’t have to worry about that, but the same result can stem from using organic fertilizers that have an acidifying effect.
Acidity and alkalinity are measured in pH units, the “pH” being a symbol for the relative steady release of nutrients to the growing plants is maintained. However, in very acid soils, this is slowed down greatly. The best pH range for utilizing organic matter is between 6 and 8.
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