How To Test And Adjust Soil pH

How To Test And Adjust Soil pH

Soil pH (potential Hydrogen ions) is the measure amount of lime / calcium in soils. PH is measured on a scale of 0 to 14 with 7.0 being neutral. Soils with a reading less than 7.0 are acidic and those more than 7.0 are alkalyne.

Different plants require different degrees of pH in order for optimal growth and production. So before adjusting or correcting the soil its necessary to first know your planting ideas and plants that the soil will support. In the case of planting or repairing a lawn, you would need to know your lawn grass type as well.

Testing The Soil

Basic test kits are inexpensive and can be found at most hardware stores, home centers, nurseries, and garden centers. They're usually very simple test tube and safe solution kits that are fairly reliable in their results. These kits also sometimes come with nutrient tests as well.

For more serious full time gardeners, there are more advanced electronic pH testers available. If you work with plants or in the garden for any amount of time, these pH testers will pay for themselves in a very short time. They're generally much easier to use and less messy because there are no chemicals or solutions.

Each test kit or instrument will have it's own specific instructions. However, the measures for adjusting and correcting the soil will all be the same. So once you have your test kit and are ready to make a test, you can start from here.

Raising Soil pH To Make It More Alkaline

Because different soil types react in different ways to lime, you will have to add more lime to clay and peaty soils than you will in sandy soils to get the same results.

To increase your pH by 1.0 point to 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 loam soils
  • Add 12 ounces of hydrated lime per square yard in clay soils
  • Add 25 ounces of hydrated lime per square yard in peat soils

Correcting an acid soil should be done as a long term project rather than trying to accomplish it in one application or season. It's very easy to overcorrect the soil. It is better to test your soil each year and make your adjustments gradually.

Of course, regularly adding organics, humus, and composts to the soil will naturally, over time, buffer and adjust the soil pH in a much better long term way. Some other organic materials for raising soil alkalynity are hardwood ash, bone meal, crushed marble, and crushed oyster shells.

Lowering Soil pH To Make It More Acidic

Like I stated before, regularly adding organics to the soil will naturally create a perfect growing medium that is easier to maintain and manipulate. This is even more true for acidic types. Most any type of compost will help acidity but some more common materials are sawdust, composted leaves, wood chips, cottonseed meal, leaf mold and especially peat moss.

If you need more immediate results, sulfur may be used to lower the pH. You should be able to find it in garden centers, feed stores, or farm and agricultural supply houses under the name of farm sulfur, dusting sulfur, or rock sulfur. To reduce the soil pH by 1.0 point, mix in 1.2 oz of ground sulfur per square yard if the soil is sandy, or 3.6 oz per square yard for all other soils. The sulfur should be thoroughly mixed into the soil before planting. Again, this should also be done gradually over a few seasons.