Composting with eggshells!
What is in eggshells that help your garden? Calcium! Calcium is a building block for cell walls in plants. Having plenty of calcium helps prevent blossom end rot on fruit. Tomatoes and squash are susceptible to this, so many gardeners put eggshells directly in the hole before they plant.
An eggshell contains about 2.2 grams of calcium.(1) It also contains 1% nitrogen and .3% phosphorous. There are traces of copper, manganese, iron, sodium, zinc, and potassium as well. Eggshells have a neutral pH level so if you need to keep your soil acidic or alkaline it wont effect your numbers by adding in the eggshells. Eggshells can take years to completely break down and benefit your soil but if you continually add them you will be doing your part in helping your soil!
How to prep your eggshells for use:
If your eggshells did not come from boiled eggs, rinse your eggshells in warm water then lay them out to dry. After they are dry you can collect them in a used coffee can or bag until you have enough to work with. You can also just add directly to your compost heap. It is more beneficial to collect and crush them all at once as they will decompose much quicker this way.
Some are concerned with the eggshell possibly being contaminated with salmonella. If your eggs shells came from hard boiled eggs you are certainly safe. If not you can simply rinse them in very warm water or bake them to kill any bacteria. 130 degrees for just 20 minutes should do the trick.
Once you have enough eggshells that they have exceeded your storage container. Use a hammer or potato masher and squish them down. When you finally have enough egg shells that mashing them down no longer makes enough space, throw them in your blender and blend blend blend! The finer they are chopped the faster they will decompose and benefit your soil.
How to use your crushed eggshells:
Simply spread your crushed eggshells around your plants in your garden. If the appearance bothers you, just work them into the soil with a hand tool. Otherwise you can wait until you harvest your crops and can till the ground.
Another method is to throw them into your compost bin. When your compost is ready for your garden the eggshells will get added then. You can throw non crushed eggs into your garden or compost bin, but it has its disadvantages. They will be an eyesore in your garden if uncrushed and will take much longer to decompose in either place. Crushing them speeds up there decomposition.
Possible pest control:
Its been said that eggshells can also be used on top of the soil to deter and/or kill crawling insects such as caterpillars and slugs. It is theorized it works like diatomaceous earth by cutting the insect. Unfortunately a study was done that proved the slugs didn't mind the egg shells at all, and were actually attracted to them more if they were not rinsed properly. (2) I have not found a study on caterpillars or other crawling insects. So as long as they are rinsed properly it really couldn't hurt to try.
Seems like a lot of work:
Really it just takes moments to prep and use your eggshells for your garden. The benefits to the soil are worth it. By using them not only are you helping your soil, but you are reducing organic kitchen waste.
(1) Butcher, G. D. & Miles, R. D. Concepts of Eggshell Quality, http://www.afn.org/~poultry/flkman4.htm