Alkaline Soil Explained: How to Identify and Fix Alkaline Soil

Alkaline soil is a type of soil with high amounts of calcium, sodium, and magnesium. All soil falls on the pH scale, which monitors the concentration of hydrogen ions and ranges from zero to fourteen. Soil with a pH level below seven is acidic soil, while soil pH levels above seven indicate alkaline soil. Alkaline soil forms from calcium carbonate-rich rocks weathering and breaking down over time. Hard water with a high mineral content can also contribute to higher pH levels.

Although some plants like clematis vines and apricot trees can tolerate higher pH levels, most garden plants require neutral or slightly acidic soil. Alkaline soil is less soluble than acidic soil, making it more difficult for plant roots to soak up necessary nutrients.

High pH levels typically hinder plant growth, especially with plants that do best in acidic soil like blueberries, rhododendrons, and azaleas. Soil alkalinity indicates a higher calcium carbonate content that produces chalky, highly porous soil. Plants rooted in alkaline soils often grow curled, yellow leaves and purple stems.

Learn how to fix the alkaline soil in your garden over time with a few different methods.

1. 1. Test your soil. Before you attempt to lower pH levels in your soil, pick up a soil test kit at your local garden center. Soil test kits range from simple pH strips to more expensive pH meters. For the most accurate analysis, send a sample of your soil to your local cooperative extension office for specialists to test.
   
2. 2. Add organic matter. The most organic way to lower your soil’s pH level is to add soil amendments. Use organic materials like mulch, pine needles, sphagnum peat moss, compost, and coffee grounds.
3. 3. Consider using acidifying fertilizers. If your soil’s pH levels are extremely high, add an acidifying fertilizer that contains elemental sulfur like aluminum sulfate or ammonium sulfate. Use acidifying fertilizer sparingly. Clay soil requires slightly more fertilizer, while sandy soil requires less. Always wear gloves, goggles, and long sleeves when working with acidifying fertilizers. Avoid direct contact with your skin. For the best results, consult a fertilizer service that can test your soil and use the correct amount of fertilizer necessary to lower your pH levels.
4. 4. Be patient. Wait several weeks before testing your soil again. It takes time for organic materials and fertilizers to soak into the soil and change the pH level. Adjust your soil slowly and avoid applying too much matter or fertilizer at once. Without careful monitoring, you can overcorrect your soil and end up with overly acidic soil.

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