Tech Notes Issue 15
Determining Whether an Acid Injection System is Warranted is Dependent on Soil and Water Tests
Acidification is a popular treatment for low quality soil and irrigation water. The most common mistake made in obtaining and using acid injection systems is a failure up front to determine if their use is appropriate.
The following are conditions where an acidifying treatment would be recommended:
1) Sodium-affected soils with poor infiltration. How severe the sodium level? Usually, an Exchangeable Sodium Percentage (ESP) greater than 15%. Additionally, adequate free lime needs to be present in the soil.
2) Water with a high adjusted Sodium Absorption Ratio (SAR) and a residual sodium carbonate (RSC) level greater than 1.25
The justification or not of using acid injection systems can be determined by your soil and water test reports.
There are several options for applying acidifying amendments including surface applied sulfur, acidifying fertilizers, sulfur burners, and direct injection of sulfuric acid into the irrigation system. For this article sulfur burners are used as an example of an injection system. Sulfur burners are generally cheaper than direct injection of sulfuric acid. In general how these units work is that a solid form of is added and then heated to form sulfite (SO3), which is a gas that then reacts with water to form sulfurous acid (H2SO3). In acid injection systems sulfuric acid (H2SO4) is used. Sulfurous acid and sulfuric acid have similar affects on soil and water.
The effect from the sulfur burner and also the acid injection systems is to react with calcium carbonate forming gypsum to prevent sodium accumulation. Additionally, the systems can drive off carbonates and convert calcium and magnesium in the water to more soluble forms. The sulfur burners are simpler to work but are often considered to be aesthetically unpleasing due to the smoke that given off and because they are located next to the irrigation pond. Attention needs to be paid to the mixing uniformity of the acidified water in the lake or pond.
Photograph: Portable sulfur burner
located on the banks of a golf course
irrigation pond. In this case the burner
was being used to lower water pH.