In Creating Healthy Soil – Part One, we discussed the five elements of good soil – minerals, organic matter, soil life, air and water. I concluded that the solution for healthy soil is to properly balance the five elements.
In Creating Healthy Soil – Part Two we covered different types of soil texture and the things you can do to improve them.
In this article I will discuss acidic and alkaline content in soil and how to amend it.
The pH level of your soil indicates whether it is acidic or alkaline. There is a test that can be performed to determine this. It involves measuring the ratio of hydrogen (positive) ions to hydroxyl (negative) ions in the water in your soil. When there are equal amounts of hydrogen and hydroxyl present, the pH is said to be neutral (pH7). When there are more hydrogen ions, the soil is acidic (pH 1 to pH 6.5). When there are more hydroxyl ions, then pH is alkaline (pH 6.8 to pH 14).
For plants to flourish in your soil the pH level should be 6.5 to 6.8. Most essential plant nutrients are soluble in that range. If the pH level is higher or lower than that range, then the nutrients chemically bound to the soil particles and they are not available to the plants. As a result, plant health suffers because the roots can’t absorb the nutrition they desire.
So it is up to you to get the pH level in your soil within the 6.5 to 6.8 range. You shouldn’t try to change pH level overnight. Instead, improve it gradually over one or two growing seasons and then make sure to maintain it every year. Adding liberal amounts of organic matter will help because they moderate pH imbalances.
If the pH level of your soil is less than 6.5, then it may be too acidic for most garden plants. Soils in the eastern half of the United States are generally acidic.
The best way to make your soil less acidic is to add limestone or wood ash. Dolomitic limestone also adds manganese to the soil and should be applied in the fall because it takes months to alter pH. Wood ash works faster than limestone and includes potassium and other trace elements. However, if you add too much the pH may be too drastically altered, which will result in nutrient imbalances. It is suggested that no more than 2 pounds per 100 square feet of wood ash be applied in the winter and then every two to three years.
To raise pH level of your soil by about one point:
· Add 3 to 4 pounds of limestone per 100 square feet in sandy soil.
· Add 7 to 8 pounds per 100 square feet in loam or good garden soil.
· Add 8 to 10 pounds per 100 square feet in heavy clay soil.
If your soil has a higher pH level than 6.8, then there is too much alkaline. In that case, you will want to acidify the soil. Soils in the western United States, particularly in arid locations, are commonly alkaline. Experts suggest you add ground sulfur or naturally acidic organic materials like conifer needles, sawdust, peat moss or oak leaves to increase the acid in the soil.
To lower soil pH by about one point:
· Add 1 pound of ground sulphur per 100 square feet in sandy soil.
· Add 1.5 to 2 pounds of ground sulphur per 100 square feet to loam or good garden soil.
· Add 2 pounds of ground sulphur per 100 square feet in heavy clay soil.
A professional soil test will not only indicate pH levels, but also levels of nutrients including phosphorus, potassium, magnesium, calcium, and sometimes nitrogen. Moreover, some labs can test for micronutrients including boron, zinc, and manganese.
Local Cooperative Extension Service offices, usually associated with state universities, offer professional soil testing. If not available in your location, you can send soil samples to independent labs for testing.
Soil samples should be taken from each garden area in the spring and fall. Many labs will provide specific organic amendments recommendations upon request.