Understanding Soil PH and Corrective Materials
When we think of improving our lawns, we often think of fertilizer.
While that is true, experienced gardeners or turf professionals know that soil pH is at the top of the list as well.
Understanding the pH scale The letters pH stand for "potential Hydrogen" and represents the measure of Hydrogen ions in the soil.
The soil pH is measured on a scale of 0 to 14.
A reading of 7.
0 in the middle represents "neutral".
A measurement of below 7 is considered to be acidic while a measurement above 7 is basic or alkaline.
An important thing to know is that each whole number on the pH scale represents a factor of 10.
That means that a soil pH of 6 is ten times more acidic than a soil pH of 7.
A soil pH of 5 is 100 times more acidic than it would be a 7.
It is not surprising that the majority of plants will grow best in a soil pH of 6.
0 to 7.
0.
There are exceptions, however.
Experienced gardeners know that it is relatively easy to alter the soil pH for plants that require different levels of acidity or alkalinity.
Active pH and Buffer pH If you have submitted a soil sample through the county extension office or directly to a testing lab, you will receive a soil analysis report.
The report will indicate the 'active pH' as well as the "buffer pH".
Active pH is the measure of hydrogen ions in the root zone.
The more hydrogen ions that are found in the soil, the more acidic the soil will be.
Where less hydrogen ions are found, the more alkaline the soil will be.
The active pH is what is measured when using an over-the-counter soil test kit.
They can be purchased in lawn and garden stores.
The buffer pH measures the soils resistance to change and can only be measured in a lab.
It indicates the amount of corrective material needed to bring the soil back to the correct pH.
For example, a low pH soil, that is heavy in organic matter or clay, would require more lime to bring it back to neutral than would be needed for sandy soil.
Since all soils are different, different amounts would be needed.
Note: It is a common belief that you can indiscriminately apply limestone to your lawn because it "improves the soil".
Limestone only improves the soil if an improvement is needed.
The purpose of limestone is to alter the soil pH and it is possible to apply too much or to over-correct.
Problems Associated with Incorrect pH Incorrect soil pH can cause many problems.
One of the more important problems is the blocking of essential nutrients.
In alkaline soils, iron (Fe) becomes bound up in a form the roots cannot take up into the roots.
An Iron deficiency is called iron chlorosis characterized by a yellowing of the plant.
Other nutrients can be hindered as well.
In low pH soils, magnesium (Mg) will be bound up.
Magnesium is essential for chlorophyll production and is what gives the grass its green color It is also necessary for carbohydrate production.
When lacking, the grass will be a pale green in color.
Products Used to Change Soil pH To make acidic soils more alkaline, we use lime.
Lime has the ability to neutralize hydrogen in the soil.
Below is a description of the different lime products often used on lawns.
When broadcasted over the surface, smaller limestone particles will work into the soil faster than larger particles.
Powdered limestone is messiest to work with, but will alter pH the fastest.
Materials for lowering soil pH When the soil is too alkaline, it may be necessary to lower the pH.
There are basically two different materials that are used: Sulfur and Aluminum Sulfate
While that is true, experienced gardeners or turf professionals know that soil pH is at the top of the list as well.
Understanding the pH scale The letters pH stand for "potential Hydrogen" and represents the measure of Hydrogen ions in the soil.
The soil pH is measured on a scale of 0 to 14.
A reading of 7.
0 in the middle represents "neutral".
A measurement of below 7 is considered to be acidic while a measurement above 7 is basic or alkaline.
An important thing to know is that each whole number on the pH scale represents a factor of 10.
That means that a soil pH of 6 is ten times more acidic than a soil pH of 7.
A soil pH of 5 is 100 times more acidic than it would be a 7.
It is not surprising that the majority of plants will grow best in a soil pH of 6.
0 to 7.
0.
There are exceptions, however.
Experienced gardeners know that it is relatively easy to alter the soil pH for plants that require different levels of acidity or alkalinity.
Active pH and Buffer pH If you have submitted a soil sample through the county extension office or directly to a testing lab, you will receive a soil analysis report.
The report will indicate the 'active pH' as well as the "buffer pH".
Active pH is the measure of hydrogen ions in the root zone.
The more hydrogen ions that are found in the soil, the more acidic the soil will be.
Where less hydrogen ions are found, the more alkaline the soil will be.
The active pH is what is measured when using an over-the-counter soil test kit.
They can be purchased in lawn and garden stores.
The buffer pH measures the soils resistance to change and can only be measured in a lab.
It indicates the amount of corrective material needed to bring the soil back to the correct pH.
For example, a low pH soil, that is heavy in organic matter or clay, would require more lime to bring it back to neutral than would be needed for sandy soil.
Since all soils are different, different amounts would be needed.
Note: It is a common belief that you can indiscriminately apply limestone to your lawn because it "improves the soil".
Limestone only improves the soil if an improvement is needed.
The purpose of limestone is to alter the soil pH and it is possible to apply too much or to over-correct.
Problems Associated with Incorrect pH Incorrect soil pH can cause many problems.
One of the more important problems is the blocking of essential nutrients.
In alkaline soils, iron (Fe) becomes bound up in a form the roots cannot take up into the roots.
An Iron deficiency is called iron chlorosis characterized by a yellowing of the plant.
Other nutrients can be hindered as well.
In low pH soils, magnesium (Mg) will be bound up.
Magnesium is essential for chlorophyll production and is what gives the grass its green color It is also necessary for carbohydrate production.
When lacking, the grass will be a pale green in color.
Products Used to Change Soil pH To make acidic soils more alkaline, we use lime.
Lime has the ability to neutralize hydrogen in the soil.
Below is a description of the different lime products often used on lawns.
- Agricultural limestone-- This is the product most often used.
It can be purchased and at farm and garden stores or farm feed stores, etc.
Agricultural limestone has less potential for burning than other lime products.
It comes in small pellet or ground (almost powder) form.
- Dolomitic Limestone-- Dolomitic limestone contains magnesium.
This is a great product for acidic soil that is low in Magnesium.
Here you knock out two birds with one stone.
Neutralize hydrogen and restore Mg levels are well. - Hydrated limestone- Hydrated lime is what is used in mortar or cement products.
It is sometimes used on lawns because it works slightly faster, but has a much greater burn potential.
Hydrated lime should not be used on Centipedegrass or other grasses sensitive to lime.
When lime is necessary, it should only be used in small amounts in the cooler parts of the year.
- Wood ashes-- Wood ashes are only 40 percent as effective as limestone, but may be a good choice when only a slight correction is needed.
However, be careful about using your garden as a place to dump ashes throughout the winter.
Some gardens recorded soil pH as high as 11.
It can take years to restore the pH back to neutral.
- Gypsum-- Gypsum is a calcium sulfate product is often used as a lime material, but it is the least effective.
While gypsum has the ability to raise the soil pH (neutralize soil Hydrogen), the sulfate in gypsum forms sulfuric acid and acidifies the soil.
The affect is that the calcium and the sulfate cancels out the affects of the other.
Gypsum has a purpose, but liming is not one of them.
When broadcasted over the surface, smaller limestone particles will work into the soil faster than larger particles.
Powdered limestone is messiest to work with, but will alter pH the fastest.
Materials for lowering soil pH When the soil is too alkaline, it may be necessary to lower the pH.
There are basically two different materials that are used: Sulfur and Aluminum Sulfate
- Sulfur- Sulfur is an age old product.
The drawback is that it can takes months to affect the pH.
It requires the activity of soil microbes to break it down first. - Aluminum Sulfate- This is the product most professionals use because it works immediately.
