The synthetic substance known as calcium nitrate is a “double salt.” Manufacturers produce calcium nitrate by applying nitric acid to limestone, then treating the substance with ammonia. The resulting crystallized material resembles table salt. Its applications include farming and technology, but it should not be confused with the kind of calcium found in edible foods and supplements. You may find the artificial fertilizer unsuitable for your garden, especially if you believe organic amendments are healthier.
Some gardeners use calcium nitrate as fertilizer in vegetable and edible gardening. Food crop applications include tomatoes and apples. Calcium nitrate is applied using the side dress or foliar method. Side dressing involves laying fertilizer along rows of growing plants or in circles around individual plants, then working it into the top inch of soil. Some hydroponics growers dilute calcium nitrate into feeding tubes to nourish plants growing in water indoors.
In foliar spraying, the gardener or farmer dilutes calcium nitrate and sprays the solution on the plants rather than on the soil to help control disease. Apple tree diseases that calcium nitrate addresses include cork spot and bitter pit. The tomato killer known as blossom end rot may also be controlled with foliar sprays of calcium nitrate. The amount of calcium nitrate needed varies depending on the plants, the growing area and the actual application method.
According to Rodale’s “The Ultimate Encyclopedia of Organic Gardening,” calcium nitrate and other chemically produced mineral salts have drawbacks. Artificial fertilizers feed plants, not soil or soil-friendly earthworms. Over time, chemical use depletes the soil, while organic fertilizers condition and nourish soils. As soil degenerates, an increasing amount of chemicals are needed to grow plants, which may potentially leach into the edible plants you consume. Ask your local cooperative extension service about the latest research on calcium nitrate to assess whether the product’s advantages outweigh its potential environmental and personal health risks.
Depending on the grade of calcium nitrate produced, the substance has uses beyond farming. Calcium nitrate is used to produce radio tubes, light bulbs and matches. It also supplies part of the chemical reaction for some fireworks and explosives.
Calcium nitrate is not safe for human consumption. Calcium fertilizers derived from animal bones, oyster shells and dolomite are also potential toxins when eaten. Some people take calcium supplements to help strengthen teeth and bones. For this purpose, common calcium formulations include calcium citrate and calcium carbonate. The mineral is also readily available in foods such as milk, milk-based foods like cheese and yogurt, tofu, blackstrap molasses and dark, leafy vegetables.
- Hydroponic Reference Center Research: Calcium Nitrate
- University of Missouri Extension: Growing Home Garden Tomatoes
- Southern Agriculture Insecticides: Calcium Nitrate Fertilizer
- University of Maryland Medical Center: Calcium
- Science Madness: Preparation of Anhydrous Calcium Nitrate
- Ultimate Encyclopedia of Organic Gardening; Fern Marshall Bradley, et al; 2009