How to Fix Acidic Soil Organically

Highly acidic soil is preferred by some types of plants, but not all. Many vegetables such as asparagus, celery and lettuce prefer a nearly-alkaline soil, as do flowers like chrysanthemums, sweet peas, dahlias and tulips. Follow these guidelines to raise the pH of your garden soil from acidic to more alkaline.

Use the soil pH testing kit to get an idea of the average level of acidity in your garden soil. You can then spot-treat areas where the acidity is stronger than this average, and use a more general pH booster elsewhere. Check the clay and sand content of your soil as well. Sandy soils tend to be more alkaline to begin with, whereas clay soils can be highly acid. Do this testing in the fall or before you plant in the spring. Soil pH can be altered slightly by what you grow, or what types of leaf mold it is exposed to in autumn.

Remove all the plant life from the soil including annuals, perennials and weeds. Till the soil thoroughly with a rototiller and check the pH again. Add the high-pH organic compost and till it so the soil and compost are fully blended.

Add the ground calcite limestone, a naturally occurring material, to the soil at the ratio of 5 pounds per 100 square feet of garden soil.

Hydrated lime is a solution of quicklime and water. The water added makes a solution of calcium hydroxide out of the calcium carbonate. Adding hydrated lime to garden soil alters its pH to an alkaline level quickly, but can also result in soil that is too alkaline.

Ensure your wood ashes come from untreated, natural wood. Add wood ashes at twice the rate of calcite limestone, as wood ash contains 50 per cent of the calcium carbonate that makes soil alkaline, compared to limestone. Wood ash would be useful and inexpensive to raise the pH of a very small garden area that is isolated from the main garden. Natural wood ashes also contain potash, a source of potassium, an important plant nutrient. Potassium helps bud, flower and fruit formation in plants.

Rendering soil more alkaline may take several growing seasons. As you adjust the soil pH toward more alkaline values, grow plants in it that prefer an alkaline soil, and plow them under for 2 seasons. These plants will also help increase the nitrogen levels in the soil, so that what you plant will engage in more vigorous photosynthesis. Your plants will be more leafy and green with slightly fewer flowers and roots. Continue to add more organic compost every season in the fall and check the pH before planting each year. Water plants well during each growing season to help dilute the acidity in the soil, and water while rototilling in the spring.