Essential Elements for Plant Growth


Biological functions:

Calcium is present in the cytoplasm at levels that would indicate that it is a micronutrient, ~0.1 µM, in order to prevent interference with the high levels of P. Nonetheless, small fluctuations in Ca levels in the cytoplasm are part of signalling mechanisms for environmental stress. Ca pumps are directed out of the cytoplasm, either to vacuoles, where it may be precipitated as calcium oxalate, or across the plasmalemma. The function of the majority of plant Ca is structural, in the cell walls of shoots and roots.

Soil Ca:

(No "organic-Ca", although some Ca may satisfy the charge of the acidic groups of soil organic matter.)

Ca Inputs to soil:

Ca Outputs from soil:

Soil Tests for Ca:

The most common soil test for plant-available Ca2+ is 1 M ammonium acetate (pH 7), which is capable of displacing exchangeable Ca2+ into the extracting solution, where it can be measured by either AAS, ICP, or even titrated with EDTA using a colorimetric endpoint. This method is not appropriate for calcareous soils (containing free CaCO3) or gypsiferous soils (containing CaSO4.2H2O) because Ca2+ will also dissolve from these soil minerals into the extracting solution. Calcium can also be measured in water extracts of soil, particularly for calculation of SAR (sodium adsorption ratio) and PAR (potassium adsorption ratio).

Calcium Fertilizers

Next Page or List of Elementsperiodic table

This page was last modified by Phillip Barak, Univ. of Wisconsin, on 5 Jan 1999. All rights reserved.