What does soil pH mean?
Soil pH is an indication of the acidity or alkalinity of soil and is measured in pH units. The pH scale goes from 0 to 14 with pH 7 as the neutral point. As the amount of hydrogen ions in the soil increases, the soil pH decreases, thus becoming more acidic. From pH 7 to 0, the soil is increasingly more acidic, and from pH 7 to 14, the soil is increasingly more alkaline or basic.
Nutrient availability in relation to soil pH
Nutrients needed in the largest amount by plants are referred to as macro-nutrients and include nitrogen (N), phosphorus (P), and potassium (K), calcium (Ca), Magnesium (Mg) and Sulfur (S). Nutrient availability is controlled by soil pH.
Most nutrient deficiencies can be avoided between a pH range of 5.5 to 6.5, provided that soil minerals and organic matter contain the essential nutrients to begin with.
If soil is too acidic or too alkaline, the nutrients present in the soil become less easily available to plants. At the same time, these extremes make other toxic elements in the soil more available. Soil that is routinely saturated with water, as ours is in South Coastal British Columbia throughout the winter, has a tendency to become acidic. Wet, acidic soil, also throws the soil life out of balance, and encourages some anaerobic bacteria, while discouraging other soil creatures. If your soil is nutrient deficient then we also sell a soil amender/top dressing which is naturally high in nitrogen and a pH of 6.8
Examples of plant pH preferences
pH 5.0 – 5.5 Parsley, Potato, Heather, Conifers, Pine, Sweet Potato, Maize, Millet, Oars, Tye, Radish, Ferns, Iris, Orchids, Rhododendron, Camellia, Daphne and Boronia.
pH 5.5 – 6.0 Bean, Brussels Sprouts, Carrot, Choko, Endive, Kohl Rabi, Peanuts, Rhubarb, Soybean, Crimson Clover, Aster, Begonia, Canna, Daffodil, Jonquil, Larkspur, Petunia, Primrose, Violet and most bulbs.
pH 6.0 – 6.5 Broccoli, Cabbage, Cannabis, Cauliflower, Cucumber, Egg Plant, Pea, Sweet Corn, Pumpkin, Squash, Tomato, Turnip, Red Clover, Sweet Clover, White Clover, Candytuft, Gladiolus, Iceland Poppy, Pansy, Rose, Snapdragon, Viola, Wallflower, Zinnea and Strawberry.
pH 6.5 – 7.0 Asparagus, Beet, Celery, Lettuce, Melons, Onion, Parsnip, Spinach, Lucerne, Carnation, Chrysanthemum, Dahlia, Stock, Sweet Pea and Tulip.
pH 7.1 – 8.0 Lilac, brassica