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Calcium - Important for Plants and People
by Debbie Peck
March 28, 2010

Many vitamins and minerals contribute to a person's good health. The importance of maintaining a well balanced diet (one that will access various food sources to obtain the recommended daily nutrient intake) can't be over emphasised as a way to prevent the onset of various health disorders.

A similar requirement for proper nourishment applies to the world of plants. Like people, plants can suffer from nutrient deficiencies which can make them "sick". One of the more interesting similarities in nutrient deficiencies between humans and plants relates to low levels of calcium.

Calcium Deficiencies

Calcium is an important mineral nutrient that is required not only in the diet of humans, but also for the normal growth and development of many different plants, particularly vegetables and fruit crops. People need calcium in order to maintain strong bones and healthy teeth. Plants need calcium inorder to complete the processes required for water uptake, cell development and cell division. Plants also need calcium for root growth and to improve the stiffness of their stems.

Calcium deficiency is routinely suffered by both men and women, but it's noteworthy that a high percentage (up to 60%) of females between the ages of 18 and 74 have low dietary levels of calcium. Osteoporosis is a disease to which many older women, who have chronic shortages of calcium, are prone. Skipping out on calcium rich foods may also cause high blood pressure. And years of calcium deficiency may result in degradation of the bones holding the teeth, which can lead to eventual loss of the teeth themselves.

Soils that are deficient in calcium can lead to many problems in the plant world. A plant with a calcium deficiency may develop weak stems and show poor overall growth. Newly developing leaves may curl at the tips and have wavy, irregular borders that might appear burned. Upper leaves may exhibit yellow spots. Flower buds may fail to develop. Plants suffering from low levels of calcium may also show reduced root growth. Fruit will develop water soaked lesions at the blossom end (blossom end rot in tomatoes is associated with low levels of soil calcium). And some plants may turn black, especially along the middle rib of the leaves if they are unable to take up sufficient levels of calcium from the soil.

Managing Calcium Deficiency

Health and Welfare Canada recommend that females over the age of twenty need approximately 700mg of calcium in their diet on a daily basis, although some research authorities suggest that 1000mg of calcium per day is a better level to strive for (men should have 800mg and pregnant women should have as much as 1200mg). Calcium rich foods that can be selected to contribute to these levels include canned sardines and salmon, yogurt, cottage cheese, almonds, hard cheese and of course milk. As well, there are many sources of calcium that people can access by eating certain types of plants including broccoli, beans (kidney, lima, navy, soy and garbanzo), kale, turnip greens, bok choy, collards and mustard greens.

Calcium deficiency in plants requires farmers and gardeners to consider making some adjustments to the soil in which they are growing their crops. Calcium can be added to the soil in the form of agricultural lime (calcium carbonate), dolomitic lime (a combination of calcium carbonate and magnesium carbonate) or gypsum (calcium sulfate). Long term solutions to a calcium deficiency in the soil include the addition of clam or oyster shells, aged manure, or rock phosphate all of which are slow release calcium sources. Wood ashes are also a source of calcium although the nutrient amounts are highly variable depending on the kind of trees that were burned to created the ash. Calcium nitrate and calcium chloride are sometimes applied to the foliage of apples and pears to prevent fruit cracking and early fruit drop. A proper soil pH will also help to reduce calcium deficiency because plants can only take up calcium readily from soils when the pH is between 6.5 and 8.5.

Gardeners who suffer from low levels of calcium in their diet should consider growing a few calcium rich vegetables in their garden. Broccoli (1/2 cup has 50mg of calcium) can either be direct seeded in the garden or can be started early indoors for transplant after the last spring frost. There are broccoli varieties that are quick to mature and others that take a full season to head up. Kale (1/2 cup has 150 mg calcium) is usually planted directly in the garden producing masses of tightly ruffled leaves that are great for salads or cooked greens. "Winterbor" Kale can be left in the garden all winter, so you'll be able to have an extended harvest if you care to dig the snow away from the row in which it is planted! Mustard greens (1/2 cup has 150mg calcium) are deeply frilled leaves that have a tempting spicy taste. They grow quickly so successive plantings, directly from seed, will produce a continuous, summer-long supply.

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