A year ago I started a study to see if eggshells decompose in soil; Eggshells – Decomposition Study. It is now one year later and time to have a look at the buried eggshells.
Decomposition After One Year
I dug up one of the baskets holding the eggshell and slowly removed the soil from around the egg. I then put the eggshell in water to rinse out the soil inside the egg, as shown in the picture above. In the process two pieces broke off the egg.
I scraped the inside of the egg to see if the inner membrane was still there, but it was gone. It had completely decomposed. This is not surprising since this membrane contains a lot of protein which easily decomposes.
The remaining shell was intact and showed no visual signs of decomposition.
One of the commenters in the post Eggshells – Decomposition Study, suggested I look at some research on eggshells found at archeological digs.
I found a report entitled “An Analysis of the Avian Fauna and Eggshell Assemblage From a 19th Century Enslaved African American Subfloor Pit, Poplar Forest, Virginia“. This is quite an interesting read from a historical perspective. The study looked at a property in Virginia that was at one time owned by Thomas Jefferson. It was a tobacco plantation that contained a small community of slaves from 1840 to 1860. Excavation of the site found thousands of eggshell fragments from both chickens and ducks, which had been raised by the community.
The key point for us is the fact that over the last 165 years, the eggshells in the soil did not decompose very much. In fact the researchers could still distinguish chicken eggshells from duck eggshells.
Do you still think eggshells decompose in the garden in a year or two?
As reported in my last post, they do decompose if they are crushed to a very fine powder in something like a mortar and pestle.
To learn more about eggshells, have a look at these posts:
- Thesis for Kathryn Elizabeth Lamzik; http://trace.tennessee.edu/utk_gradthes/1635/