© 2007 Donald G. McGahan (aka soilman) All Rights Reserved
Calcium is a macronutrient essential for all plants. The ability of a soil to supply calcium to plants is intimately tied to soil acidity (and for agricultural soils, to liming).
Calcium as a Plant Nutrient
- Ca Demand by plants high
- second only to N and K
- Calcium is the most plentiful cation on the exchange complex of nearly all soils
- very acidic are the exception as they have a high aluminum saturation
- Deficiencies of calcium are quite rare for most plants, except in very acid soils.
- Calcium is immobile in the plant and when calcium deficiency does occur, it is usually associated with growing points (meristems) such as buds, fruits and root tips.
- Certain plants show Ca deficiency, even when the soil pH is adequately maintained by liming.
- Such deficiencies are often related to the transport of Ca in the plant.
Calcium in the soil is found mainly in three pool.
- calcium-containing minerals (such as calcite or plagioclase)
- calcium complexed with soil organic matter
- calcium on the clay and organic colloids.
The cycling of calcium among these and other soil pools, and the gains and losses of calcium by such mechanisms as plant uptake, liming and leaching comprise the calcium cycle.
Significant losses of calcium and magnesium occur from the soil by:
- Crop removal
- Soil erosion.
The total loss from all three causes in humid-region agricultural soils, expressed in the form of carbonates, approaches 1 Mg/ha per year.