In this post, I will tell you how use eggshell to improve soil fertility. Eggshells contain a number of minerals that ate essential to plant growth, most noble calcium, which plays an important role in the strength and thickness of plant cell walls. Sufficient calcium in the soil also helps prevent blossom end rots. Researchers in the Netherlands studying the mineral composition of chicken eggs found that powered eggshells were, on average, 39.15% calcium, 0.4% nitrogen, and 0.38% magnesium. All of these nutrients are essential to plant health.
Before using eggshells in our garden, we rinse them and microwave them for 2 minutes to kill possible pathogens like salmonella. After collecting eggshells for a few weeks, we grind them into a powder. You can use a coffee grinder. The calcium in eggshells is in the form of calcium carbonate, which is not plant available. So, we don’t use eggshells as a quick fix for calcium deficiencies, but instead as a slow release of calcium and other minerals. For a quick fix, you can create soluble calcium from eggshells using an acid like vinegar, but we’ve never found it necessary.
We incorporate our eggshells into our worm bins and compost piles, and rely on the microbes and earthworms to break down the calcium and make it plant available over time. Of course grinding the shells into a powder speeds up this process significantly. The fine eggshell particles are small enough for worms to ingest and provide a source of grit that aids in the worm’s digestion. In addition, a sufficient supply of calcium is critical to worm health and reproduction, which leads to more nutrient-rich castings for the garden.
Finally, end rot is not really caused by a calcium deficiency in the soil, but instead by a plant’s inability to efficiently move water, and therefore calcium, throughout the plant body. Adding eggshells to your garden will reduce the likelihood that an actual calcium deficiency in the soil is responsible for blossom end rot.