How I use Eggshells to fertilize my Organic Garden.
Over the last year I have been investigating the science behind garden practices methods and products in the Testing Garden Assumptions Series.
As a part of this series I have taken a look at a number of resources often sighted as being able to be used to fertilize your garden. I focused on free and local resources because I wanted to see if I could be a little more sustainable and hopefully fertilize my garden for years to come for free.
In order to analyze the fertilizer potential of a material I look at two main areas. The organic macro nutrients such as Nitrogen Phosphorus and Potassium that are required in higher concentrations and the trace elements or micro nutrients that are equally as important however required in significantly smaller concentrations.
Plants require or gain benefit from 21 elements of these 15 are commonly tested for in our analysis. Of the 6 remaining some are not commonly tested for while others such as Carbon, Oxygen and Hydrogen are gasses that are in consistent concentrations in our atmosphere.
So far free and local resources that have shown fertilizer potential are Coffee Grounds, Tea Leaves, Comfrey, Autumn Leaves, Wood ash or Woodchips and even Human Urine. Today I thought I would take a look at another commonly recommended organic amendment Eggshells.
The main recommendation is that eggshells are made primarily of Calcium Carbonate and calcium is required by many plants and is critical for things such as healthy tomato production helping to avoid things like blossom end rot.
The assumption that eggshells have high concentrations of calcium is quite correct. Researchers in the Netherlands had eggshells from a number of sources analyzed and found that the concentration of calcium in eggshells averaged around 390 mg/g or 39% of the shell.
The calcium in eggshells is not immediately available to plants. It needs to be in its elemental form as appose to the calcium carbonate. Some sources recommend treating eggshells with vinegar or acetic acid to release the calcium. Unfortunately while egg shells will react with vinegar it does not release the elemental calcium it simply binds it and neutralizes the acid.
Testing Garden Assumptions Playlist:
Research paper from the Netherlands:
Other interesting research:
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