3 Sustainable Ways to Make Your Soil Less Acidic

Small changes in pH levels can affect how well plants are able to reproduce and take up nutrients. These changes can also alter how exposed they are to soluble pollutants such as aluminum. Some plants can tolerate a wide range of soil pH, while others thrive in a more narrow range—sometimes more acidic, sometimes more alkaline.

This article gives you three sustainable ways to lower the acidity of your soil so that your plants can grow more comfortably in it. Plus, we disclose one common, unsustainable method to avoid, and a few tips on preventative measures to keep your soil well-balanced.

The Science of Soil Acidity

Some soils are more acidic than others. Soil formed from granite and sandstone tends to be more acidic than soils formed from limestone. This is because limestone mostly consists of calcium carbonate, the same compound found in antacids.

Water in soil leaches out alkaline elements such as sodium, calcium, and magnesium. Because of this, soils in rainy regions and sandy soils (which drain easily) are likely to be more acidic than clay soils (which retain water) or soil in dry regions. Healthy loam soil is likely to be neutral.

Heavily farmed soils can also become acidic, as nitrogen and sulfur fertilizers increase the acidity of soils while crops take up alkaline nutrients and leave acidic soil behind.

When to Lower Soil Acidity

There are a number of ways to determine your soil's pH level to know if you need to lower the acidity.

You can use the old-fashioned method of smelling your soil. There are also ample DIY methods to test your soil's pH, and you can also find low-cost pH tests at local garden centers or send your soil to your state's cooperative extension service.

Whether or not you need to lower the acidity, or raise the pH, of your soil depends on the kinds of plants you want to grow. If you want hydrangeas to produce blue flowers or want to grow healthy blueberries, you'll want acidic soil with a relatively low pH of 4.0 to 5.0. Potatoes, apples, azaleas, and junipers also do better in acidic soils.

On the other hand, most lawn grasses prefer slightly “sweet” (alkaline) soil, while most garden plants, especially vegetables, prefer relatively neutral soil between the pH levels of 6 and 7.5.

Signs You Need to Alkalize Your Soil

Examining your plants can help you determine whether or not your soil needs to be less acidic.

• Your plants are stunted or dead (never a good sign!). Aluminum is more soluble in acidic soil, and too much aluminum can kill plants or stunt their growth.
  
• Weeds and mosses tolerate acidic soil better than other plants, not because they necessarily prefer acidic soil, but because they can thrive in lower levels of soil fertility, often caused by low pH levels.
  
• Acidic soil can make it more difficult for your plants to absorb essential nutrients like potassium, magnesium, calcium, and molybdenum, a clear sign of which is chlorosis, or a lack of chlorophyll. Normally green leaves will appear yellow or splotchy, have scorched tips, or become cupped.
  
• Acidic soil makes phosphorus uptake more difficult as well. Phosphorus is necessary for photosynthesis and for seed and fruit production. New leaves may be stunted, or seeds and fruit may be underdeveloped.

What to Avoid

When alkalizing your soil, skip the lime.

Applying lime is by far the most frequently recommended way to make soil less acidic, but it's also the method with the largest carbon footprint. Garden lime is made from limestone, which is quarried then heated in kilns to produce calcium carbonate. Both mining and heating have high energy requirements, burning diesel fuel during mining and transportation, and burning coal or natural gas to produce 2000-degree temperatures in kilns.

3 Sustainable Methods

Here are more sustainable alternatives for making your soil less acidic.

Compost Mix

A compost mix contains essential nutrients that are often lacking in acidic soil. The air pockets in compost allow water to slowly trickle through the soil, retaining essential nutrients. Compost also supports microorganisms like healthy soil bacteria, which can help raise the alkaline level of the soil.

Wood Ash

In the fall, clean out your fireplace and apply the wood ash to your soil. Wood ash is rich in much-needed potassium. Be sure to lightly fork the ash into the soil so that it doesn't blow away.

Mushroom Compost

Mushroom compost isn't made from mushrooms. It's made for mushrooms, which prefer alkaline soil. Mushroom compost contains a high degree of chalk (calcium carbonate), which makes the compost alkaline in nature while also providing organic matter to enrich your soil. Just don't overdo it: mushroom compost is rich in soluble salts, which can harm or kill germinating seeds.