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| Egg shells (J. Harasewych) |
Post-Easter, even after deviled eggs, egg salad, potato salad, and breakfast burritos you still have the shells. Questions about using egg shells in the garden to prevent blossom end rot in tomatoes brought many comments on the Master Gardener Facebook pages in addition to questions from relatives and friends. Here's some research-based information.
*Also, check the link below for a suggestion to provide calcium for backyard birds. (They make eggshells, too.) from Audubon. "Your breakfast discards can serve as vital nutrition for females as they make their own eggs." No research-information found on safety of artificially dyed eggs. If you use natural dyes all is clear.
This is a common problem with both green and ripening tomatoes. This shows up as a black or brown sunken area at the end of the fruit. It is caused by low levels of calcium in the soil or inconsistent watering. An excess of nitrogen in fertilizer (the "N" in fertilizer numbers N-P-K, e.g. 5-10-5 = 5% Nitrogen, 10% Phosphorous, 5% Potassium, the balance is filler) supports foliage and can cause a problem.
If you had a soil test, and Calcium levels are in the medium (801 to 1,200 lbs. Ca/acre) or high range (>1,200 lbs. Ca/acre), soil should be good for growth. Calcium helps root and leaf growth and production of firm tomatoes.
Here is an informational article about egg shells and calcium from Christopher Enroth, Extension Educator, Horticulture, University of Illinois Extension.
Enroth notes "For years, eggshells have been recommended as an amendment to soils and containers due to their high calcium content. Some gardeners who grow tomatoes swear by adding six or more eggshells in the planting hole, with the idea that the extra calcium will reduce blossom end rot of tomato fruit. Other gardeners compost their eggshells to add calcium to their finished compost. So do eggshells make a difference? Or is this egg wash?"
The Answer
Yes, adding egg shells does work but most gardeners miss a critical step. Thanks to Jerry Harasewych, one of my favorite researchers, for his step-by-step experiment and photos.
Egg shells need to be ground to release the calcium. They can be ground in a mortar and pestle but they are still chunky pieces. These larger pieces, although smaller than just crush shells, take a long time to dissolve and release calcium.
They can be ground in a coffee grinder and the result is finely ground eggshells. A research study in Alabama found finely ground shells performed as well as pure calcium and outperformed agriculture lime.
Enroth also says, "Don't have a coffee grinder but still have an abundance of eggshells? Another trick is to boil 10 to 20 eggshells and then let the concoction sit overnight. The next day strain the eggshells out of the water, and you have liquid calcium solution. Each eggshell adds four milligrams of calcium. Two cups of the solution per plant should be adequate. Apply about every two weeks. (Ref: Gillman, 2008)"
The Lackawanna County, PA, Master Gardeners share information about watering and calcium in tomato plants.
"Blossom-end rot happens when a number of conditions come into place. The disease is especially prevalent when rapidly growing plants are exposed to wide fluctuations in water amounts. Calcium cannot be taken from the roots to the rest of plant and sustain healthy tomatoes. The fruit doesn’t have the necessary nutrient and the bottom of the tomato begins to rot. Other factors include a pH out of range and damage done to the roots from cultivation too closely. Heavy applications of nitrogen will contribute to blossom-end rot.
Other Tips
To manage blossom-end rot, take these steps:
Tread lightly around the roots of the plants to avoid damage.Water consistently if there's a lack of rain, about 1"per week. Water slowly at the plant base.Add mulch to your garden, this conserves moisture.Use fertilizer low in nitrogen.Do not spray any type of pesticide, as this is not a symptom of insect, bacteria, or fungi damage pesticides are ineffective on blossom-end rot.Consider a soil test, this will give you a complete analysis of what your garden needs and will give you a head start for the next growing season."
** Special thanks to Jerry Harasewych for his grinding experiment and the photos.
* Audubon link:
https://www.audubon.org/news/give-nesting-birds-calcium-boost-saving-your-leftover-eggshells
~ Carol Kagan
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