Understanding Lime Application

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When lime and fertilizers are applied to soils, the onset of many chemical reactions takes place. Some occur instantly, and others take months to occur. These chemical reactions have a major influence on how efficiently lime and fertilizers are utilized by growing plants, when they should be applied, and pronounce the economic returns from their usage. By understanding the nature of these chemical reactions, in relationship to soils, we can determine how to use lime, and fertilizer as well, to our benefit.

Surface area of soils exposed to contact with lime and fertilizer is key to making the most of soil amendments. The amount of clay present in a given soil, largely determines the surface area available. Most of a soil’s potentially reactive surface area is made up of clay particles, and clay particles per given volume, have more surface area than sand, silt or loam. The mineral forms of individual soil particles and the extent to which these particles have been coated with layers of oxides  and organic materials, also affect the total soil reaction.

All clay particles in soil have a negative net electrical charge(-). With this negative charge, clay particles will react with components of lime, and fertilizer that dissolve into soil as positively(+) charged particles, or cations, when added to the soil. Lime particles dissolve to release positively charged calcium( Ca++), or magnesium(Mg++) in the case of dolomitic limestone.

These positively charged particles, or cations, are attracted to the negatively charged particles present in soils. This process occurs when lime is applied to soil, and it reacts with soil moisture to dissolve. The rate at which lime dissolves, releasing these particles, is directly related to how fine the limestone is ground, and the chemical form of the limestone. Calcium oxide is burned lime, and calcium hydroxide is hydrated lime. These forms of limestone react much quicker in the soil, than do calcitic, or dolomitic limestones, because they are more soluble in water.

Calcium or magnesium particles are attracted to and held captive by clay particles, after lime dissolves in soil, thus neutralizing soil acidity, and raising soil pH. Due to this captivity, lime does not move downward in soils very rapidly, especially in our clay dominated soil profiles. For this reason, lime can be applied anytime in Burke County without any losses from soil leaching. It remains a good idea, however, to apply it well enough in advance to adequately react with the soil, and reduce acidity, prior to planting or establishment.