How to Measure and Adjust PH in Garden Soil

Soil pH is referred to as the acidity of the soil and is measured by the number of Hydrogen ions present in the soil.

When the soil pH is too acidic (low pH) or alkaline (high pH), nutrients present in the soil become locked-up or unavailable. Correcting the pH has the same effect as applying fertilizer as it unlocks plant nutrients already present, and it is more cost-effective as well. 

Some garden plants thrive in acidic soils while others prefer alkaline soil. The acidity or alkalinity of soil is measured by pH (potential Hydrogen ions). pH is a measure of the amount of lime (calcium) contained in your soil, and the type of soil that you have.

A picture of hands holding soil over a garden bed.

A soil with a pH lower than 7.0 is an acidic soil and one with a pH higher than 7.0 is alkaline.

Farmers used to taste their soil to determine its pH. A sweet taste or smell, it was alkaline. A sour taste meant it was acidic. Wasn’t a good idea then, and it’s not a good idea now. See: Test Garden Soil Yourself

How to Measure Soil pH

It is recommended that you use relatively inexpensive Soil pH Meters and follow the manufacturer’s instructions when testing the ph Level of your Gardens soil.

How to Adjust Soil pH

To raise or lower the pH level in the soil either Limestone or Sulfur is utilized. There are other materials that will do the job also, but the aforementioned are the most widely used.

Limestone is added to soil raise the pH level because limestone is essentially calcium and calcium reacts with water in the soil to yield hydroxyl ions .. a process known as, hydrolysis… thus the pH level in the soil is raised. Scroll down to Application of Lime

Sulfur reacts with bacteria in the soil and produces sulfuric acid, which releases hydrogen ions thus causing the soil to become more acidic….. the pH level is lowered. Scroll down to Application of Sulfur

How to Use Lime to Increase pH in Soil

To increase your pH by 1.0 point and make your soil more alkaline.

Add 4 ounces of hydrated lime per square yard in sandy soils

Add 8 ounces of hydrated lime per square yard in loamy soils

Add 12 ounces of hydrated lime per square yard in clay soils

Add 25 ounces of hydrated lime per square yard in peaty soils

The addition of ash, bone meal, or crushed oyster shells will also help to raise soil pH levels.

Using Sulfur to Lower pH in Soil

If your soil needs to be more acidic, sulfur may be used to lower the pH if it is available.

To reduce the soil pH by 1.0 point

Mix in 1.2 oz of Garden Sulfur per square yard if the soil is sandy

Mix in 3.6 oz per square yard for all other soils.

Composted leaves, wood chips, sawdust, leaf mold and peat moss, will also help to lower the soil pH.

Optimal Soil Ph for Fruits and Vegetables

Almost all vegetables prefer well-drained soil, rich in organic matter slightly acidic side. A safe pH range for Almost all vegetables is 6.0 to 6.5 pH. However – there are exceptions to all rules, and optimal results require a more precise tracking and maintenance of soil ph. It’s not half as complicated as some people would like to make it sound. The pH requirements in the scrolling menu at the top of this page give the maximum and minimum range, so long as you stay within these parameters you’ll be fine.

pH for Vegetables and Fruit

Common Vegetable & Fruits
Artichoke6.5 -7.5
Asparagus6.0 -8.0
Bush Bean6.0 -7.5
Beets6.0- 7.0
Blueberries4.5 – 5.5
Broccoli6.0 – 7.5
Brussels Sprouts6.0 – 7.5
Cabbage5.8 -6.2
Cantaloupe5.5 -7.0
Carrots5.5 – 7.5
Cauliflower6.0 – 7.0
Celeriac5.5 – 6.5
Celery5.5 -5.5
Chicory5.0- 7.5
Corn5.5 -7.0
Cranberry3.5 – 5.0
Cucumber5.5 – 7.5
Eggplant5.5 – 6.0
Endive5.5 – 6.0
Garlic5.5 – 7.5
Horse Radish6.0 -7.0
Kale6.0 – 7.5
Kohlrabi6.0 – 7.5
Leek6.0- 8.0
Lentil5.5 – 7.0
Lettuce6.0- 7.0
Mushroom6.5- 7.5
Muskmelon5.8 -6.2
Mustard6.5 – 7.5
Onion6.0 -7.0
Parsnip5.5 -7.0
Peas6.0- 7.5
Peanuts5.0 -6.5
Peppers5.5 -7.0
Potato4.5 – 6.0
Raspberries5.6 – 6.2
Rhubarb6.0 – 6.8
Shallot5.5 -7.0
Soy Bean5.5 -6.5
Spinach6.0- 7.5
Tomato6.0 -6.8
Watercress5.0 -8.0
Watermelon6.0 – 6.8
PH for fruits and vegetables

pH for Flowers and Ornamentals

Flowers & Ornamentals
Amaryllis5.5 – 6.5
Azalea6.0 -7.5
Baby’s Breath6.0- 7.0
Balsam4.5 – 5.5
Begonia6.0 – 7.5
Caladium6.0 – 7.5
Candytuft5.8 -6.2
Canna5.5 -7.0
Carnation5.5 – 7.5
Chrysanthemum6.0 – 7.0
Cockscomb 5.5 – 6.5
Coleus5.5 -5.5
Cornflower5.0- 7.5
CornCosmos5.5 -7.0
Daffodil3.5 – 5.0
Dahlia5.5 – 7.5
Day Lily5.5 – 6.0
Easter Lily5.5 – 6.0
Four-O-Clock5.5 – 7.5
Foxglove6.0 -7.0
Geranium6.0 – 7.5
Gladiolus6.0 – 7.5
Hollyhock6.0- 8.0
PH for flowers
Iris6.5 – 7.0
Larkspur6.5 – 7.0
Lupine6.5 – 7.0
Marigold6.0 – 7.5
Nasturtium6.5 – 7.0
Narcissus6.0 – 7.5
Pansy6.5 – 7.0
Perwinkle6.5 – 7.0
Petunia6.5 – 7.0
Phlox5.0 – 6.0
Poppy6.5 – 7.0
Salvia6.0 – 7.0
Shasta Daisy6.0 – 8.0
Snapdragon6.0 – 7.5
Sweet Alyssum6.5 – 7.0
Sweetpea6.5 – 7.0
Sweet William6.5 – 7.0
Tuberose6.0 – 7.0
Tulip6.0 – 7.0
Verbena6.0 – 8.0
Zinnia5.5 – 7.5
PH for flowers