Why pH Matters

A Basic Explanation of pH in Soil

Knowing your soil pH is important if you expect to have healthy plants and a good vegetable harvest.  The pH of the soil is an indicator of the availability of nutrients in the soil that your plants need to grow.  For example the availability of phosphorus (P), the P in NPK, is affected by soil pH both too high and too low.  When the soil pH is too high, above 7.5, phosphorus will form compounds with calcium and magnesium.  At pH values below 6.5 phosphate ions react with aluminum and iron.  When these compounds form the phosphorus is no longer available to your plants.  Generally speaking, a good pH range for your soil will be between 6.5 and 6.8, however some plants do better at different levels.  See more below.

How to Measure Soil pH

There are various ways to test your soil pH.  You can buy soil testing kits and soil pH meters.  You can find plenty of these kits and meters on Amazon.  If you want to get all DIY, you can use red cabbage, vinegar, and baking soda.  If you don’t feel comfortable going this route you can always have your soil professionally analyzed.  A quick Google search will provide you with plenty of examples of DIY home soil pH testing.

Adjusting Soil pH

If your soil has a pH above 7.5 it is considered alkaline and you will want to adjust the level downward.  Adding organic matter is the best way to lower you soil pH.  If your soil is acidic, a level below 6.5, lime or ground limestone is often used to rase your soil pH.  If your test results show that your soil is really acidic and needs adjusting by over 1 point it may be best to bring in soil and use raised beds.  Raised beds avoid the problems associated with poor soil quality.  Also, depending in what you intend to grow, each bed can target a specific pH range that is best suited to that particular crop.  For example blueberries prefer a soil pH of 4.8 to 5.5 whereas onions do better between 6.0 and 7.0. 

A List of Common Plants and Recommended pH Levels

Alpine strawberry (5.0-7.5)

Artichoke (6.5-7.5)

Arugula (6.5-7.5)

Asparagus (6.0-8.0)

Basil (5.5-6.5)

Bean, lima (6.0-7.0)

Bean, pole (6.0-7.5)

Beet (6.0-7.5)

Blackberry (5.0-6.0)

Blueberry (4.5-5.0)

Broccoli (6.0-7.0)

Brussels sprouts (6.0-7.5)

Cabbage (6.0-7.5)

Cantaloupe (6.0-7.5)

Carrot (5.5-7.0)

Cauliflower (5.5-7.5)

Celery (6.0-7.0)

Chervil (6.0-6.7)

Chinese cabbage (6.0-7.5)

Chive (6.0-7.0)

Cilantro (6.0-6.7)

Collard (6.5-7.5)

Corn (5.5-7.5)

Cranberry (4.0-5.5)

Cucumber (5.5-7.0)

Dill (5.5-6.5)

Eggplant (5.5-6.5)

Endive/Escarole (5.8-7.0)

Fennel (6.0-6.7)

Garlic (5.5-7.5)

Horseradish (6.0-7.0)

Jerusalem Artichoke/Sunchoke (6.7-7.0)

Kale (6.0-7.5)

Kohlrabi (6.0-7.5)

Lettuce (6.0-7.0)

Melon (5.5-6.5)

Mustard (6.0-7.5)

Okra (6.0-7.5)

Onion (6.0-7.0)

Oregano (6.0-7.0)

Pak choi (6.5-7.0)

Parsley (5.0-7.0)

Parsnip (5.5-7.5)

Pea (6.0-7.5)

Peanut (5.0-6.5)

Pepper (5.5-7.0)

Potato (4.5-6.0)

Pumpkin (6.0-6.5)

Radicchio (6.0-6.7)

Radish (6.0-7.0)

Raspberry (5.5-6.5)

Rhubarb (5.5-7.0)

Rutabaga (5.5-7.0)

Sage (6.0-6.7)

Sorrel (5.5-6.0)

Spinach (6.0-7.5)

Squash, summer (6.0-7.0)

Squash, winter (5.5-7.0)

Sunflower (6.0-7.5)

Sweet potato (5.5-6.0)

Swiss chard (6.0-7.5)

Tarragon (6.0-7.5)

Tomatillo (6.7-7.3)

Tomato (5.5-7.5)

Turnip (5.5-7.0)

Watermelon (6.0-7.0)

Further Reading

http://www.rodalesorganiclife.com/garden/understanding-ph

http://www.extension.umn.edu/agriculture/nutrient-management/phosphorus/the-nature-of-phosphorus/

https://en.wikipedia.org/wiki/Soil_pH