Acidic Material for Growing Blueberries

Growing Conditions

• Because blueberry shrubs require such an acidic soil to grow well, gardeners find it difficult or labor-intensive to raise blueberries successfully in regions with soil that is not already naturally acidic. Although it is easy to modify neutral soils -- those with a pH around 7.0 -- with soil amendments, it is an ongoing maintenance task. Changing naturally alkaline soils to become more acidic is an expensive proposition and is usually not successful or pragmatic in the long term.

Acidic Soil Amendments

• The best way to lower soil pH to grow blueberries is to amend the soil with acid-forming organic matter. Although any organic matter benefits a soil by making it more fertile and improving its texture and moisture-retention qualities, only those materials that decompose to create acidic soil should be used in blueberry garden beds. Oak leaf mold, rotted conifer needles, pulverized conifer bark, peat, pine sawdust or coffee grounds consistently lower soil pH when used as a mulch or a soil amendment.

Synthetic Fertilizers

• Manufactured fertilizers, comprising salt compounds, may be added to soil to create an ideal pH range for blueberry plants. Blueberries do not grow well in soils that provide nitrogen in the form of nitrate; most garden fertilizers contain the compound ammonium nitrate, which is not ideal for blueberries. Blueberry shrubs prosper when nitrogen is available in the form of ammonium without nitrates, such as that supplied by the fertilizer ammonium sulfate. Sulfur-coated urea and aluminum sulfate also work well. The sulfur ions in these fertilizers help to make soil more acidic.

Tips

• Adding organic matter to soil or laying acid-forming organic matter atop the soil can reliably lower the pH of soils that are already acidic or neutral. Even with the addition of organic matter or the application of ammonium sulfate, alkaline soils may not effectively change into the desired pH range of 4.5 to 5.5. Always conduct a soil test on soils that are being modified in pH. Over-application of synthetic soil conditioners can create salt build-up that may harm blueberry plant roots. In regions with alkaline soil, it may be more feasible to haul in acidic soil and grow blueberries in raised beds rather than investing time and resources to try to amend native soil to become more suitable for acid-loving plants.