- One of the 13 essential elements for plant growth and is one of the 6 Major Elements, based on concentration required
- calcium is needed in much greater quantity than all the other elements combinedIG
- calcium is naturally abundantIG
- principle form of uptake: ionic form (Ca2+)
- amount required for healthy plant growth: 5,000 ppm, 0.5%, dry soil matter
- soils with too much free calcium carbonate (CaCO3) are known as calcareous, and have very high pH (8.2+)
- calcium & magnesium determine the soil’s mechanical properties
- the amount of calcium versus magnesium on the exchange points determines if the soil is open & airy or loose or tight & airless (too much Mg means tight & airless soil)
- this ratio also determines if the clay portions cling to themselves or open and separate
- If Ca is in excess, and Mg is deficient, soil is extremely loose; water flows through without sticking; getting Mg levels to target will improve this
- also, this ratio has much more effect on the soil’s air supply than does organic matter
- when calcium:magnesium ratio is correct, less compost is needed
- ideal ratio for non-calcareous soil: Ca:Mg = 68:12
- for calcareous soil: Ca:Mg = 85:5
- calcareous soils are often deficient in phosphorous
- soils over-fertilized with calcium and/or potassium are often deficient in magnesium (Mg)
- Calcium is available to plant roots in its ionic form: Ca2+
- calcium is the strongest of the cations, which means that it can knock other cations off of the exchange points in the soil (see Cationic Exchange Capacity for more info)
- Ca2+ primarily moves through soil via mass flow, but also via diffusion
- Brix test, using a refractometer, will show a fuzzy line of demarcation when calcium levels are sufficient (per Phil Nauta)
- soil factors that affect calcium uptake by plants:
- available levels in soil
- decomposition of organic matter
- plant factors that affect calcium uptake by plant:
- hybrid or variety of plant
- stage of growth
- interactions with potassium (K) and magnesium (Mg) and other elements
Deficiency Symptoms:
- thick, woody stems
- cell death at the base of the leaves
- soil conditions related to calcium deficiencies:
Roles of Calcium in Plant Functions:
- involved in the osmotic potential, balancing anions, controlling membrane permeability & electropotential
- important for maintaining cell integrity and membrane permeability
- enhances pollen germination and growth
- activates enzymes for cell growth and division
- may be important for protein synthesis and carbohydrate transfer
- it may also help to detoxify the plant from heavy metals (chelation?)
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