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Adjusting pH in Your Garden

Written by Stephanie on July 10th, 2017

If you have ever sent soil from your garden to a soil lab for analysis, you will find pH somewhere in the results they send back.  “pH” refers to potential hydrogen, or the hydrogen ion concentration of soil.   Most garden soils have a pH of between 5.5 and 8.  When you look at your results, remember that the larger the number is, the more alkaline the soil is.  Conversely, the smaller the number is, the more acidic it is.  Seven is considered neutral. Most plants grow best when the soil pH is between 6-7.5.

Depending on what crop you are growing, you may need to make your garden more acidic or more alkaline.  Changing the pH of the soil is a slow, gradual process.  It generally takes several seasons to move the pH to where you need it to be.  The limestone or sulfur needs to be tilled in to a depth of four to six inches so the roots of the plant can reach it.

The easiest way to treat your soil is to first till your garden down to a depth of six inches.  Spread the material over the tilled dirt with a drop spreader (one of those push fertilizer machines that spews out fertilizer as you push it across the yard.) at the rate recommended by the soil lab.  Then till the material into the tilled soil until it is evenly distributed four to six inches under the surface of the dirt.  .  Whatever material you choose to spread, use gloves when handling it or you may have problems with skin irritation.

What type of limestone do you need to add to your soil?  That depends on what nutrients the soil needs.  You add dolomitic limestone if your soil is low in magnesium.  Dolomitic limestone contains both calcium and magnesium.  They are important nutrients that your garden plants will need to grow.  The dolomitic limestone makes it easier for plants to absorb all the nutrients they need to grow well.

Pulverized limestone is common and cheap.  You can use it when your garden has enough magnesium and calcium in it. Spread it over the garden using the method mentioned above.

Pelleted pulverized limestone is more expensive than regular limestone.  However, it is cleaner, less dusty, and easier to work with than the other two types of limestone.  It is more effective, too.

Sulfur only comes in a fine dust or as a part of another compound, such as magnesium sulfate or ammonium sulfate.  When using powder, be sure and use a face mask to keep from breathing it.  Be sure to follow all the instructions on the package as far as safety precautions to take.

All of these products need to be watered in after they are applied to make them more effective in neutralizing the acid or alkaline components.

The pH of the soil is important because it determines how much of a vital nutrient a plant can absorb.  In highly acidic soils, aluminum and manganese become very available and may poison the plant.  Calcium, phosphorus and magnesium become much harder for the plant to absorb.

If the pH is more than 6.5, phosphorus and almost all of the micronutrients become unavailable to the plants, no matter how much of them are in the soil.


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