Are Eggshells Good for Planting?

Soil Conditioning

• Eggshells are mostly calcium carbonate, so many gardeners assume that they will add calcium to the soil, raising the pH level of acidic soils. According to a 2005 study at Auburn University, hand-crushed eggshells had little effect on soil pH, although eggshells mechanically ground to a very fine powder did raise the soil pH as effectively as lime. For the home gardener, though, pulverizing the shells finely enough to provide results is a challenge due to lack of proper equipment. Although adding eggshells to your garden won't harm the soil, the strategy is unlikely to significantly alter the soil pH.

Nutrients

• Eggshells have trace nutrients, such as nitrogen, found in lingering egg material. These nutrients may benefit the soil slightly. Unfortunately, gardeners would have to add eggshells in large quantities to produce significant results. Eggshells do not take the place of soil amendments, such as compost or manure, or fertilizer, for providing the nutrients plants need.

Slugs

• Jeff Gillman of Washington State University challenged the idea that eggshells deter slugs. According to Gillman, eggshells are not effective as slug repellents. The idea of using eggshells as a slug deterrent probably arose because diatomaceous earth does deter slugs. This product has sharp edges, just as broken eggshells do, but it is not the sharp edges that deter slugs, but rather the dessicating properties of the diatomaceous earth.

Recommendations

• Although egg shells won't hurt the soil, they lack few real benefits for planting. Egg shells spread over the planting area create an untidy appearance, as well. Compost egg shells instead. When combined with other plant and food scraps, they'll break down into a rich, nutrient-dense plant food.