Lighter soils with low cation exchange capacity may not hold adequate magnesium where it is needed. Soils derived from parent materials void of magnesium also may be deficient. In these situations, a readily available, water soluble source of magnesium may be needed. One of the 16 essential elements for plant growth and development, sulfur is used by all plant tissue for protein synthesis and is a component of some of the amino acids that are the building blocks of proteins. Soil tests for sulfur are not always reliable.
Sulfur exists in several oxidation states in the soil.
Sulfur recommendations often are based on crop removal data. Some state crop specialists suggest an application of 20 pounds per acre annually as a standard practice. The typical application rates for K-Mag in most crops is 200 to 600 pounds per acre. However, exceptions to this range may occur depending on special circumstances. Nutrients of K-Mag will be in the form available to the crop in a matter of days when the soil moisture and temperature are suitable for plant growth.