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Water Soluble Calcium: another recipe for regenerative agriculture

Here I will share a method, inspired by Korean Natural Farming, for how to make Water Soluble Calcium (WCA). Calcium is one of the most common minerals in the world though it is usually found in a solid state such as eggshell, shellfish, pearl, snail shell, chalk, and limestone. This article provides a simple method for making water soluble calcium along with suggestions for how to use WCA as part of your natural farming practice.

Photo: Water Soluble Calcium: raw vinegar and toasted eggshells produce a water soluble calcium solution. Credit: Sarah Montaño

Calcium is extracted from calcium carbonate found in eggshells using vinegar. When calcium carbonate (CaCO𖾔) reacts with acid, it produces carbon dioxide (CO₂). The acetic acid in vinegar is a weak acid so the reaction happens slowly and an imperceptible amount of (CO₂) is produced. You may notice some bubbling, indicating that the reaction is occuring. Notice that the eggshell becomes fluffy or spongey after the (CO₂) is released and the calcium is dissolved in the vinegar solution. At this point, the reaction is complete and the eggshells may be composted or applied as mulch in the garden.

The importance of calcium in regenerative agriculture:

Calcium helps to form cellular membrane and supports smooth cell division during periods of growth. Fruits that are rich in calcium have a balanced growth cycle; they are plump and have body yet do not split or become disfigured. They tend to be more firm and can be stored for long periods of time. Foods that are rich in calcium are essential for a healthy ecosystem and regenrative agriculture because they are more resistant to pests and disease.

Calcium-rich fruits and vegetables are vital sources of nutrition for the animals and people that consume them.

We know that calcium is an essential mineral for building bones and structure within the body.

Calcium also helps humans to eliminate toxins from the body because it has the ability to bind to harmful substances. For example, oxalic acid is found in many edible plants. Oxalic acid is a mycotoxin produced by the fungus aspergillus and the common yeast candida and forms in some plants as a defense against predation. Oxalic acid has the ability to bind to minerals and metals to form oxalates. Humans are susceptible to the bioaccumulation of oxalates in the body which can cause a whole range of issues including kidney stones and heavy metal poisoning.

Calcium has the ability to bind to soluble forms of oxalic acid to make it insoluble, allowing for elimination through the organs and facilitating the prevention of the formation of oxalic crystals.

Symptoms of calcium deficiency in plants:

  • Leaves turn brown and then dry out.

  • Empty seed or bean pods

  • Fruit has cracks and splits in the skin

  • Root vegetables are hollow, dull, and rot quickly

  • Fruit and vegetables lack crunch and body

  • Grains are watery and low in starch and lack fragrance

  • Lack of luster and fragrance in fruiting body

  • Low resistance to insect and disease

  • Underdeveloped roots

How to make WCA


  • 1 -64 oz. mason jar or ceramic vessel

  • Porous paper or cloth & rubber band

  • 1 - 750ml upcycled wine bottle & cork to store WCA

  • funnel


  • Dried eggshells or oyster shell.

  • Fermented vinegar such as brown rice. We use raw vinegar made from Gingerhill sugar cane.

Environmental Conditions:

  • Fairly stable ambient temperature of about 73℉ to 77℉.

  • Shaded place with no direct sunlight.


  • Collect organic eggshells and allow them to dry out

  • Remove the membrane from the eggshells:

  • Heat a frying pan over a medium flame.

  • Gently crush the eggshells into medium/large pieces.

  • Roast the eggshells to burn away organic membrane. About 30-40 minutes.

  • Roasted eggshells become lighter in weight and brighter in color.

  • Roasted eggshells can be stored in an airtight container for future use.

  • Fill the mason jar/ceramic vessel with 10 parts vinegar. Then incrementally add the roasted eggshells. The proper ratio of vinegar to eggshells is 10:1.

  • For example you may use 5 cups vinegar to ½ cup eggshell.

  • The eggshells may move up and down, emitting bubbles, as calcium carbonate dissolves and carbon dioxide is released.

  • Cover the container with cloth or paper and secure with a rubber band.

  • Allow to sit in a shaded area, with ambient temperature of about 73℉ to 77℉ for several days.

  • The process is complete when there is no more movement of the eggshells and no more formation of bubbles. About 7 days.

  • Strain the liquid from the eggshells and funnel into 1-750ml upcycled wine bottle & cork.

  • Some eggshells may still contain calcium carbonate. When there are too many minerals for the vinegar to dissolve, the solvent reaches a point of saturation. You may remove the finished solution and add more vinegar to the eggshells.

How to use WCA in natural farming & regenerative agriculture

  • Dilute completed WCA solution. Dilution ratio of WCA to water is 1:1000.

  • WCA is very useful in the fruiting phase of the plant when the plant transitions from vegetative phase to the fruiting or reproductive phase.

  • Apply as a foliar and flower spray to fruiting crops in order to help promote the yield of solid fruits with balanced sizing.

  • Use WCA when you notice that fruit is splitting or cracking.

  • Use WCA to stimulate the growth of a crop that is slow to develop during sprouting or vegetative state.

  • Use WCA to enrich a crop that is leggy or overgrown.

  • Use WCA when leaves of a plant lack luster or are brown or pale in color.

  • Use WCA when fruit growth is slow.

  • Use WCA when flavor and sugar content is decreased.

  • Use WCA when flower buds are irregular or disfigured.

  • WCA has the potential to improve the taste and fragrance of a crop when combined with other natural farming supplements such as seawater and calcium phosphate ( WCP).

  • Combine WCA, Fish Amino Acid (FAA), WCP, and seawater. Apply to soil before planting a new bed.

Natural farming methods are an extension of the kitchen. By utilizing simple ingredients such as vinegar, sugar, eggshells, fish scraps,and rice we are able to propagate indigenous microorganisms, make our own fertilizers, and grow our own food without the use of any petrochemicals. Up-cycling spent ingredients and materials from the kitchen, like glass bottles and cooking scraps, also helps us to practice a zero-waste lifestyle. Next week I will detail a method for how to make water-soluble calcium phosphate (WCP).


  1. Cho, Ju-Young. Natural Farming: Agriculture Materials. Cho Global Natural Farming, 2010.


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