How and Why to Lower or Raise Soil pH

One of the first things that most gardeners learn is that plants need good soil — or excellent hydroponic nutrients — to thrive. Rich, fertile soil with lots of organic matter provides your garden with an excellent foundation. But enjoying all the benefits that foundation offers depends on its pH. Understanding pH basics can help you achieve peak plant performance and exceptional harvests in soil gardens and hydroponics.

The pH scale ranges from 0 to 14, with a neutral midpoint at 7.0.

Basics of pH for Plants

The pH scale is the same whether you measure pH in garden soil, nutrient solutions or the foods and liquids you drink yourself. Technically, pH stands for the "power" or "potential" of hydrogen and reflects the concentration of hydrogen ions in a solution.

The pH scale runs from 0 to 14 with 7.0 as the neutral midpoint — and the pH of pure water. Substances with pH below 7.0 are called acidic. Substances with pH above 7.0 are called basic or alkaline. The lower the number of the scale, the higher the hydrogen concentration.

It's important to understand that small changes in pH represent big changes in your soil. With pH, a shift of 1.0 reflects a 10-fold change. A shift of 2.0 reflects a 100-fold change, or 10 times 10.

This means soil with a pH of 6.0 is 10 times more acidic than 7.0. But 5.0 pH indicates conditions 100 times more acidic than a pH of 7.0.

 Tomatoes grow best when soil pH is in the 6.0 to 6.8 range.

How pH Affects Plant Nutrition

Proper pH levels in garden soil or hydroponic solutions are crucial to plant nutrition. When pH moves outside optimal ranges for your plants — whether overly high or low — reactions happen between nutrients that affect their availability to your plants.

Even if your soil or nutrient solution is packed with essential macro and micronutrients, pH can prevent your plant from accessing sufficient quantities of those nutrients. And plant nutrition suffers at every stage of plant growth.

Most plants grow well in the slightly acidic to near-neutral range of 6.0 to 7.0 pH. In that range, most essential plant nutrients in soil or nutrient solutions stay readily available to plants. At lower pH ranges, when soil is acidic, some nutrients such as phosphorus become less available. But iron, copper and zinc become more available at those levels. Plants like blueberries are often called "acid-loving" plants because they thrive in low-pH soil.

How to Test Your Garden's pH

Testing soil pH is a simple process. Most garden centers and online retailers offer soil pH meters that provide approximate pH readings when you stick the probe into your soil. More sophisticated equipment is available as well. But to remove all the guesswork and ensure an accurate starting point, submit your soil to a soil lab for testing.

Your local county extension office can help with information and economical testing kits that ensure you get precision results and recommendations for the crops you grow.

If you grow hydroponically, pH is still critical to nutrient availability. Garden centers and hydroponic shops carry various products to test pH levels in hydroponic systems, from simple test strips and liquid test kits to digital pH meters with Bluetooth technology. Depending on the type of hydroponic system you use, you may want to test the pH in your reservoir or in the solution that drains from growing media.

Many garden retailers sell all-in-one meters that provide general measures of soil pH, moisture and light.

How to Raise or Lower pH for Plants

Once you identify pH levels, don't delay corrections. When pH gets outside the optimal ranges for plants, nutrient deficiencies or even toxicities can result. For overly acidic soil, your soil test results may recommend adding lime to restore pH balance to your soil. In overly alkaline soil, incorporating elemental sulfur works to lower soil pH and restore nutrient availability. Changing soil pH takes time. Always follow test recommendations for the amount of soil amendments to use.

In hydroponic gardens, you can adjust the pH of your nutrient solutions more quickly and easily. Earth Juice products eliminate the need for messy liquid adjusters, so you can opt for simple crystallized alternatives instead.

Earth Juice Crystal pH Up helps make your solution less acidic. Earth Juice Crystal pH Down makes your solution more acidic. Remember, a small change can have a big impact. Add crystals in small quantities, mix thoroughly and check your pH as you work.

Once you have your garden at optimal pH for your crops, keep it there. Soil testing for vegetable gardens and lawns should be done every two to three years. For hydroponics, test pH regularly so the nutrients you feed always stay available to your plants.

For 30 years, Earth Juice has been helping growers and gardeners optimize plant nutrition at every stage of plant growth. Let us help you take your garden to the peak of performance, productivity and pH.

Always read product labels thoroughly and follow instructions, including application or dilution rates and recommended feeding frequency for your plant phase and feeding method.