Trace Elements for Lawn and Landscape - Questions and Answers

Question: What are trace elements?

Answer: Trace or, as they are also called, minor elements, are materials absolutely essential to healthy growth in plants, but which are needed only in trace or infinitesimal amounts. Among the more important trace elements are boron, copper, iron, manganese, molybdenum and zinc. A plant growing in soil deficient in any one of these will eventually develop definite abnormalities. Each element, therefore, is absolutely vital to the health and well-being, of plants. Most of them act as catalysts or “helpers,” in the chemical processes inside the plant.

Question: Are trace elements lacking in most soils?

Answer: No. As a rule sufficient quantities of the minor elements are present in most soils to supply the plants’ requirements. There are, however, many areas in the United States where certain minor elements are either completely absent, or are in a form which the plants cannot use. Very sandy soils which are low in organic matter, soils that have received an overdose of hydrated lime, or soils in natural limestone areas are most likely to be deficient.

Question: Can trace element deficiencies be diagnosed easily?

Answer: Only an expert can easily diagnose trace element deficiencies in plants. He does this on the basis of symptoms present and by means of special tests on the plant tissues themselves. A machine known as the spectrograph is also used at some agricultural experiment stations to solve nutritional problems in plants. Most any gardener, however, can learn to recognize the principal deficiency symptoms by observing their plants closely and by studying the deficiency symptoms illustrated in a good book on the subject.

Question: Which trace element is most frequently deficient?

Answer: Iron is the trace or minor element most frequently deficient. For this reason many products have been developed in recent years to overcome iron deficiency. According to one expert, a deficiency of iron occurs on some outdoor plant in every state of the Union. Ornamental plants such as azaleas (rhododendrons), mountain laurel, andromeda and trees like pin oak and cottonwood are among the most susceptible to iron deficiency. Even turf grass in many parts of the country can suffer from a lack of iron.

Question: Why is iron so important?

Answer: Iron is essential in the formation of the all-important chlorophyll, even though it does not actually form a part of the chlorophyll molecule. And of course chlorophyll is needed to form sugar and other carbohydrates needed for normal plant growth. Though only infinitesimal amounts of iron are needed, plants will show marked deficiency symptoms when this element is unavailable.

Question: What symptoms does an iron deficiency produce?

Answer: When iron is only mildly deficient, the leaves of many plants, particularly the young ones at the growing tips, become yellow or chlorotic, with the veins usually remaining green. The symptoms are more striking, however, in cases of severe iron deficiency when iron is completely unavailable. Under such cir- cumstances even the veins lose their green and turn an ivory color. The leaves fall prematurely, growth is stunted and, if iron is not supplied, the plant soon dies.

Question: What factors favor iron deficiency?

Answer: Iron becomes unavailable or cannot be absorbed by plants when:

• The soil is highly alkaline and the excess of calcium or phosphate changes the iron to an insoluble form which cannot be used by the plant
• The soil is poorly aerated, as in heavily compacted soils, and when the drainage is poor (in both situations the roots cannot function normally and thus cannot absorb iron)
• Excesses of soluble manganese and copper are present

Question: What chemicals can one use to overcome an iron deficiency?

Answer: There are several excellent materials for this purpose. Most widely publicized in recent years are the so called iron chelates which are a combination of iron and organic acids. This combination keeps the iron from changing to an insoluble and, hence, unusable form after it is applied to the soil. In other words, in chelated form the iron stays in solution and in a form available to plants even under adverse conditions. The iron chelates are applied either dry to the soil around iron deficient plants and watered in, or they may be applied as leaf sprays.

Question: Are there other materials besides chelates for supplying iron?

Answer: Yes, there are many. A chelate-like iron complex containing ferrous ammonium sulfate, other trace elements and nitrogen. When 5 pounds of this substance are applied to 1000 square feet of “run-down,” starved lawn, the grass turns green and begins to make lush growth within a few days. Other materials used for supplying additional iron which have been available for a long time are iron ammonium citrate and iron sulfate.

Question: Can trace elements such as iron be beneficial to crops which do not show an iron deficiency?

Answer: Yes. Minute amounts of extra iron and other minor elements have resulted in better crops. In New Jersey, for example, yields were increased in corn, tomatoes, escarole and white potatoes where these crops were side dressed with an iron chelate at the irate of about 12 ounces per 1000 square feet.

Question: Can the newer iron compounds be used to advantage on alkaline soils?

Answer: It soon may be possible to grow certain plants in soils which previously could not support such plants. In the alkaline soils of the Great Lakes area one may be able to grow azaleas, blueberries and rhododendrons, provided the proper kind of iron in the proper amount is supplied to the soil, and is replenished from time to time as needed. The high lime soils of the Southwest are also be capable of producing normal-looking plants with the iron compounds.

Question: Can you overdose with these new iron compounds?

Answer: Definitely. Severe injury to plants can result from adding excessive amounts of any iron compound, either to the soil, or in sprays applied to the leaves. Avoid heavy applications and apply the material uniformly to assure an even distribution. Injury from excessive applications will appear as irregular gray to brown spots on the leaves, or the leaves may drop prematurely.

Question: Is all leaf-yellowing (chlorosis) due to an iron deficiency?

Answer: Gardeners must not jump to the conclusion that all leaf-yellowing is caused by a deficiency of iron. Chlorotic leaves may also result from fungus, virus, insect or mite attack; low temperatures; toxic materials in the air or soil; excessive soil moisture; or even surpluses or deficiencies of other trace elements such as copper, manganese or zinc. Correct diagnosis is therefore essential to ensure preventive or curative results with iron compounds.

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