One thing most hunters see in their report when they get there soil surveys back is that their soil pH is low. This publication’s Dirt on Dirt takes a look at what exactly a soil pH is and why it can be detrimental to your habitat management goals.
The soil pH is a measure of how acidic your soil is. The pH of your soil will affect the growth of plants on your property and the microorganisms in the soil that help the plants grow. As most know, a low pH value means the soil is acidic and a high pH means the soil is basic. Both of which can be a bad thing for your soil. The pH of a soil a soil affects the availability of nutrients that plants need to grow. The graph below shows the important nutrients involved in plant growth and how soil pH affects their availability in the soil. The most effective pH for a soil is right in the middle between 6 and 7. Figure 1 shows the common classes of soil pH. The pH also affects the activity of microorganisms that help make nutrients available for the plants to use. A bad pH can also make some pesticides ineffective.
So how does a soil become acidic?
It can be grouped into four main categories. The first one is the direct addition of acidic H+. Most of this occurs naturally because of the growth of plant roots or when ammonium fertilizers are added to the soil. The second practice is the creation of carbon dioxide. This occurs when microorganisms break down dead plant material or when rain passes through the soil. The third practice is the removal of basic cations from the soil through leaching. The final practice is the addition and decomposition of organic materials, again a process that happens naturally. As one can see most of the processes that create an acidic soil happen natural, which is why it is important to continuously monitor your soil pH.
How to fix an acidic or basic soil?
The best thing to do to fix an acidic soil is apply lime. Lime is very effective in neutralizing an acidic soil. The reaction works better when the soil temperature is warm and when there is a lot of moisture in the soil. Your local soil testing laboratories will be able to tell you how much lime should be added to your soil based on the clay content and organic matter present. Fixing a basic soil, however, is a lot harder. Some soils can be fixed with an application of acidic organic materials or by using a source of sulfur, but that can get very expensive. Adding gypsum and then allowing it to be leached through the soil with irrigation water is also a common practice, but can cause some concern about downstream runoff. It is better for a land owner in this situation to find plants that are more capable of growing in a high pH soil.
In the next publication we will take a closer look at high pH (salty soils) and what plants to grow in those soils.
Figure 1
Extremely Acidic
Very Strongly Acidic
Strongly Acidic
Moderately Acidic
Slightly Acidic
Neutral
Slightly Alkaline
Moderately Alkaline
Strongly Alkaline
Graph
Figure 1
Extremely Acidic
Very Strongly Acidic 4.5-5.0
Strongly Acidic
Moderately Acidic 5.6-6.0
Slightly Acidic
Neutral
Slightly Alkaline
Moderately Alkaline 7.9-8.4
Strongly Alkaline
Graph