Nutrient availability and pH coupling
Soil pH (acidity or alkalinity) controls whether nutrients are chemically available for plant roots to absorb. At pH 6.5, most macronutrients and micronutrients are available. Acidic soils (below 6) bind phosphorus and molybdenum unavailable. Alkaline soils (above 7.5) lock up iron, manganese, and zinc.
Different plants have evolved to thrive in different pH ranges. Blueberries and rhododendrons (ericaceous plants) require acidic soil (4.5-5.5) where aluminum availability supports their growth. Vegetables and most field crops prefer neutral (6-7) for balanced nutrient availability.
Lime and sulfur amendments for correction
Adding lime (calcium carbonate) raises soil pH over months to years by neutralizing acidity. Sulfur lowers pH by oxidizing to sulfuric acid. Both changes are slow; pH adjustment requires planning ahead.
Lavender and other Mediterranean plants thrive at pH 7-8 (alkaline soils). These plants have adapted to calcareous soils where limestone bedrock keeps pH high. Trying to grow blueberries in pH 7 soil requires major amendment (sulfur) or container gardening with acidic potting mix.
Soil testing and field-specific management
Soil testing reveals existing pH and nutrient status. A field may be suitable for wheat (pH 6-7) but unsuitable for potatoes without lime (which worsens scab disease). Test results guide lime rates and timing.
Some perennial crops (orchards, berry fields) are costly to re-establish; choosing pH-compatible species at planting avoids years of failed establishment or expensive amendment. Annual crops allow more flexibility: switch to pH-tolerant crops rather than amending low-value land.