Calcium is a low-key essential nutrient that carries a heavy load in plant growth. Too often, it takes a backseat as soil fertility programs are developed for many high-yield and high-quality crops. Peanut and tomato growers are probably exceptions in their emphasis on good calcium nutrition.

Functions of Calcium in Soil
In soil, calcium replaces hydrogen (H) ions from the surface of soil particles when limestone is added to reduce soil acidity. It is essential for microorganisms as they turn crop residues into organic matter, release nutrients, and improve soil aggregation and water holding capacity. Calcium helps enable nitrogen-fixing bacteria that form nodules on the roots of leguminous plants to capture atmospheric nitrogen gas and convert it into a form that plants can use.

Functions of Calcium in Plants
Calcium, along with magnesium and potassium, helps to neutralize organic acids, which form during cell metabolism in plants. Calcium also plays a role in other key plant functions:

Improves the absorption of other nutrients by roots and their translocation within the plant
Activates a number of plant growth-regulating enzyme systems
Helps convert nitrate-nitrogen into forms needed for protein formation
Is needed for cell wall formation and normal cell division
Improves disease resistance.

Calcium Deficiency
Calcium deficiencies are most likely to occur in acid, sandy soils from which calcium has been leached by rain or irrigation water. It may also occur in strongly acid peat and muck soils where total calcium is low.

Calcium deficiency is not likely for most crops when the soil is properly limed to adjust soil pH to optimum levels for crop production. As soils become more acidic, crop growth is often restricted by toxic soil concentrations of aluminum and/or manganese — not a calcium shortage. Soil testing and a good liming program are the best management practices (BMPs) to prevent these problems.

Calcium deficiency can be prevented by following several BMPs such as soil testing on a regular basis and correcting soil acidity with proper liming. Balance the plant nutrition program by keeping calcium, potassium and magnesium available in a balanced supply. An overabundance of one can lead to a shortage or uptake (antagonism) of another. Also apply calcium for specific plant functions. For example, calcium applied when peanuts begin to set pods can help improve seed development.

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