Magnesium and Calcium: keystone elements for plant health

Soil testing

Soil testing

Australian soils are notoriously deficient in calcium and magnesium. A simple soil test carried out by a soil testing lab will confirm if your soils are indeed inadequately balanced. I personally think it is worth the expense (somewhere between $50-$200 per test) if you’re serious about gardening ornamentals or edible plants, or growing healthy pasture.

You need to know what your soils are made of. Deficiencies in soils lead to stressed plant that will attract pests and diseases. These in turn will cause you lots of grief.

Calcium and magnesium are amongst the most needed nutrients for plants to uptake other nutrients. It has to do with their cation exchange capacities (their positive electrical charge) which, in short, binds to other nutrients.

Role of calcium in plants

  • Participates in metabolic processes of other nutrients uptake.
  • Promotes proper plant cell elongation.
  • Strengthen cell wall structure – calcium is an essential part of plant cell wall. It forms calcium pectate compounds which give stability to cell walls and bind cells together.
  • Participates in enzymatic and hormonal processes.
  • Helps in protecting the plant against heat stress – calcium improves stomata function and participates in induction of heat shock proteins.
  • Helps in protecting the plant against diseases – numerous fungi and bacteria secret enzymes which impair plant cell wall. Stronger Cell walls, induced by calcium, can avoid the invasion.
  • Affects fruit quality.
  • Has a role in the regulation of the stomata.

Role of magnesium in plants

Magnesium is an indispensable mineral for plant growth, for it plays a major role in the production of chlorophyll, on which photosynthesis depends. Without a ready source of magnesium the plant cannot grow.

  • Chlorophyll formation
    • Light-absorbing green pigment
    • Capture’s the energy of sunlight and turns it into chemical energy
    • Allows synthesis of organic compounds that are useful for plant growth and functioning (carbohydrates, lipids, proteins)
  • Synthesis of amino acids and cell proteins
  • Uptake and migration of phosphorus in plants
  • Vitamin A and C concentrations
  • Resistance to unfavourable factors (drought, cryptogamic disease)

So, it is good practice to sprinkle a handful of dolomite lime per square meter of soil prior to planting a new crop. Dolomite lime brings calcium as well as magnesium. Garden lime (cheaper) only brings calcium. Both types of lime help raise the pH. Soil pH are, in general, best around 6.5-7. Our veggie patch soils at the farm started at pH 4 (rather acidic) and now four years of soil improvement later, we’re at 6.5.

Another practice that I would recommend is to dilute Epsom salt (Magnesium sulphate) in a spray bottle (1/4 teaspoon for two cups of water) and apply as a foliar spray in the late afternoon, when the sun is no longer shining on plants, once a fortnight. This will give your plants an extra magnesium boost that helps with chlorophyll production. Strong chlorophyll metabolism lead to strong plants that pump a lot of energy and can grow big, healthy and resilient.

Finally, I also spray once a fortnight seaweed solution. I mix that solution with Epsom salts and spray once – that saves time. Plants get a real kick out of that and soils too.

Last but not least, organic matter. Add generous amounts of it, regularly, to feed the soil biota (aka soil life such as bacteria, fungi, arthropods, etc.).

Happy soils – happy plants – healthy gardener.

Come and talk to us gardeners at the Dooralong Produce Swap, 3rd Sunday of the Month, Dooralong Oval, 3pm!

Or sign up to our permaculture course to learn EVERYTHING YOU NEED TO KNOW about soils! How to analyze them, restore them, feed them, nurture them…

2017 Part-Time PDC (web)

2017 Part-Time PDC

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