Eggshells, Bones and Vinegar – Water-Soluble Calcium and Calcium Phosphate (WCA / WCP)


In this post i’ll teach you how to make water-soluble calcium (WCA) and water-soluble calcium phosphate (WCP) then show you some of our results using it in the garden on sugar cane and groundnuts (i.e., peanuts).

I first learned about making WCA/WCP back in Hawaii and had good results using it there on tomatoes. As far as natural farming soil amendments go, WCA/WCP are simple and can be made very quickly and inexpensively with limited materials. WCA/WCP have the benefit of being water soluble, which allows the plant to quickly make use of it, as opposed to slower solid forms of Calcium and Phosphorous that can take longer to break down (e.g., crushed eggshells, limestone, etc.).

The water-soluble calcium (WCA) is sprayed on during a plants reproductive stage, when plants are flowering, and helps make fruits and veggies hard and sweet, which can help prevent blossom end rot in tomatoes, for example. The water-soluble phosphorous (WCP) is sprayed on during vegetative growth phases of plants so they can produce a lot of “structure” like strong roots, stems, leaves etc. Knowing that the soils here in Gambia can use all the help they can get, and that we have easy access to eggshells and animal bones, we thought we’d give this a shot. I’ll explain it ‘Gambian style” below (i.e. w/o brown rice vinegar, grill or oven etc.) but if you’d like to see a more detailed write up you can check out the Hawaiian Natural Farming crew’s article at:

Click to access SA-10.pdf

Ok, let’s check out how we made and used WCA/WCP.

Water-soluble Calcium (WCA) is first. Eggshells are all calcium but its locked up in the shell and unavailable to the plant. We’ll figure out a way to pull the calcium off the shell and get it to the plants. First step, get a fire going and gather your eggshells. Rinse the eggshells clean so there’s no more membrane or slime in there that could contaminate things. We got our eggshells from a nice man named Mr. Jallow, he cooks breakfast here in Farafenni.


Put the crushed eggshells on the fire. Note: this fires a little big, normally you would want to roast them a little slower, as you’re trying to avoid blackening them in favor of browning them a little.


Stir the eggshells frequently so the heat is evenly distributed and they don’t burn at the bottom.


Try to get all the eggshells lightly roasted to a brown, not charring them into black carbon chunks. You can see them here in the mayonnaise jar, which cost about $2.75 when it had mayo in it.


Next up is our water-soluble calcium phosphate (WCP). It’s essentially the same process as WCA, but you use animal bones that have phosphorous in them. First step is to get some old animal bones. A butcher may be a good spot, leftovers from steak night, or you can often buy bones from the supermarket. In Gambia we found a lot of goat and cow bones easily so decided to use them. Here is my counterpart breaking them up into smaller pieces.


We didn’t have a grill or oven so Momodou improvised with some old corrugate roofing. He’s stabbing holes in it with his knife.


Put the chunks of bone over the fire and grill them. Mix them up as they cook and try to get them to a light brown, again trying not to burn them black.


Now we have our browned eggshells and bones cooled and collected. We’re ready for the next step.


To get the calcium and calcium phosphate off the eggs and bones we use vinegar, which starts a reaction that releases the calcium, as well as carbon dioxide. Ideally, and according to Natural Farming proper procedures, mandates, laws etc. :), you’d use brown rice vinegar (BRV). We couldn’t find that so we used the local brand vinegar we have here and still had good results. Natural farming says use whats around you so that’s what we tried. One option in the future would be to try to make our own vinegar, which would eliminate bringing another store bought item onto the farm and probably be more ‘natural,’ maybe with some better nutrients or vitamins in there that this vinegar doesn’t have.

Ok, so the mix is 1:10, by weight, eggshells to vinegar (e.g., 1oz eggshells mixed into 10oz vinegar). If you want to eyeball it and leave the scale alone you can fill a jar 2/3 full with vinegar and then add eggshells till the jar is full. The eggshells will emit carbon dioxide so get ready for bubbles, a bad smell, and the mixture to possibly bubble out over the top. Just go with it and think of all that great calcium going into the vinegar. Below is Momodou pouring the vinegar over the eggshells and bones.


Here is my other counterpart Modou with some WCA. You can see the bubbles from the CO2 being released. Modou confirmed that it smelled bad 🙂 and was weird: perfect! If someone is looking at you strangely, you know you are making it correctly and doing interesting things!


After you’ve added the vinegar – put a breathable cover over it (e.g., paper towel and rubber band) and store it in a cool dry place for 7-10 days. Write the date on the paper towel. If after 7 days there are no more bubbles its ready to use. If the bubbles are still there, add some more cooked eggshells or bones and let it sit for another day or two.


To use WCA/WCP dilute it 1:1000 (i.e. around a 1.25 tablespoon in 5 gallons of water). If you’re here in Gambia with me that equates to about a 1/3 attaya glass in a standard 20L bidong. Good luck getting someones attaya glass to put this stuff in (it does look like attaya). Use the WCP first to get the plants structure going – apply to the leaves in the evening and watch the plants grow fast. After the WCP, use WCA when the plants start to flower and fruit.

Ok, now lets see what WCA/WCP can do when applied to sugar cane and groundnut ( i’ll quit writing ‘peanut’ in parentheses now – you guys get it 🙂 ).

First we’ll look at some sugar cane beds. Big thanks go out to my Hawaii farmer friends, especially ginger john, for teaching me about sugar cane and how to grow it, cut it, process it etc. These beds were a small tribute to the island and the start of my quest to collect and share sugar cane juice with friends here. Sugar cane in Hawaiian is “Ko” which means “salt” in Mandinka. Sweet and salty.

The bed on the right in the photo below received WCA/WCP treatments. All the plants were sown at the same time and were the same size when we transferred them into these two beds. We also put a lot of good stuff in these beds, as the sign shows – some manure, compost and carbonized coos husks (i.e. biochar). This photo is a week or so after we transferred them. You can already see that the bed on the right, with the WCP applied, is a little taller. We called it ‘cane of sweet’ to try to keep its identity hidden, as a way to prevent theft. It worked for a little while :).

11 July 13

A couple weeks later.

12 July 26

A couple weeks later the trend looks the same – more vegetative growth in the WCA/WCP bed. At this point we were only applying WCP to help vegetative growth, as the flowers/reproductive stage had not come.

13 Sept 1

Taller still. Luckily most people thought this was corn and didn’t steal it. If people knew it was sugar cane they would jump the fence and steal it to chew on. This happened later on.

14 Sept 23

Final photo of the sugar cane below. It’s now bearing seed and received some WCA. You can see that the bed on the right has clearly done better – growing both taller and a little greener during the few months.

15 Oct 13

And now we can take a look at our groundnut beds. The photo below shows 2 beds: the one on the left was being given WCA/WCP at appropriate times and the one on the right wasn’t. Both beds were identical except for the WCA/WCP with respect to initial plant size, sun, water, initial bed preparation (e.g., adding compost).


You can see below that there’s a big difference between these two beds. Even the weeds we’re going wild in the WCA/WCP bed on the left. One thing we noticed was that almost immediately after adding WCA or WCP – the day after – we’d see 50-100 small weeds pop up. Almost like the WCA/WCP woke them up. We were really impressed with how well it worked, especially on this groundnut.


Thank you for reading and participating with my service in this way. Feel free to comment or ask questions below. -stephen

7 thoughts on “Eggshells, Bones and Vinegar – Water-Soluble Calcium and Calcium Phosphate (WCA / WCP)

  1. Mike

    Hey – to toast up those things I’d suggest using a perforated drum like a coffee roaster or bingo machine (or make one out of a tube, pot, or can) anything that can be rotated. If you can put that drum inside of a pot like a rotisserie, and the pot on coals, I bet you can toast them to the perfect shade of brown you want without a scorch on them. If you have the material sitting on the metal – even if you stir it constantly, they’ll scorch.

    • Good idea, yeah if we could get a rolling barrel or something going that would be nice. We’ve got a lot of big tomato past cans here that would probably work for that. Like roasting coffee beans huh? Thanks for the tip.

  2. Thanks Stephen.
    I searched all the day for eggshell/vinegar ratio and finally I have the answer: “mix is 1:10, by weight, eggshells to vinegar”.
    I will use, probably, apple vinegar.
    Have great farming.

    • Sure np. I think most of these preparations can be stored indefinitely, the ones with sugar may need some sugar added once in a while. My rule of thumb is to just keep it around for a year or less, and make a new batch if I need.

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