Liming soils

By Wayne Flanary | University of Missouri Extension
Submitted to Corner Post

Liming acid soils can increase yields, for example, research from changing the pH from 4.5 to 6.0 increased soybean yields by fifteen percent. The benefit of liming comes from increasing the soil pH to the crop’s favorable range for growth.

There are many other benefits to liming such as availability of nutrients, increased efficiency of fertilizers applied to soil, favorable microbial activity, and better soil structure and tilth.

Nature and farming causes soil acidity. Organic matter breakdown, dissolved nutrients, removal of calcium and magnesium and replaced with hydrogen, and the addition of nitrogen fertilizers creates soil acidity.

When a soil is limed, limestone reacts with the soil, and acidity is removed. Hydrogen ions are exchanged with the calcium from the soluble limestone. The hydrogen is then in the soil solution and reacts with the carbonate and forms carbonic acid. Carbonic acid is not stable in soils and further breaks down to carbon dioxide gas and water.

Many think calcium is key to reduce acidity. However, without the carbonate, the soil would still contain the acidy hydrogen ion and pH would not change. For example, gypsum does not reduce soil acidity.

Also, other products are sold as pH adjusters. Many of these are liquid products containing chelated calcium. These products have essentially no effect on soil pH.