Acids and bases—commonly referred to as alkalis—play a pivotal role in plant physiology. Their influence ranges from subtle adjustments that promote healthy growth to dramatic changes that can damage or even kill foliage.
In the 1980s, before the Environmental Protection Agency (EPA) introduced stricter emission limits, acid rain—primarily formed from sulfur dioxide (SO₂) and nitrogen oxides (NOₓ) released by coal and natural‑gas combustion—devastated forests. Elevated trees in the United States and elsewhere suffered leaf loss, weakening the canopy from the top down.
A balanced pH—ideally between 6.0 and 7.0—provides a stable environment for nutrient uptake. Studies show that soils with too low a pH (acidic) can scorch leaves and produce weak stems, while soils that are too high (alkaline) often yield uneven foliage, deformed fruit, and premature death.
Regional soils already contain varying levels of acidity or alkalinity, which determines what crops can thrive locally. Gardeners can tailor growth media by adjusting the pH to match the needs of specific plants.
Commercial fertilizers are rated by their nitrogen, phosphorous, and potassium content—for example, a 15‑16‑17 blend. According to research from the University of Massachusetts Amherst, 215 lb of calcitic limestone is required to neutralize the acidic impact of one ton of this fertilizer. A 15‑0‑15 formula, on the other hand, can raise the soil pH by up to 420 lb of limestone.
While most species thrive near neutral pH, some, like evergreens, azaleas, blueberries, and rhododendrons, prefer acidic soils. Conversely, many annual crops favor slightly basic conditions.
