In the world of fertilizer management in Minnesota, some nutrients such as N,P,and K work to improve crop yield and/or quality. Others don’t have any effect on production and, therefore, can be classified as recreational nutrients. Many of the micronutrients fall into the category of being classified as recrearional. When thinking about fertilizer use, for the 2009 crop year, it would be good to review and summarize the microntrients and their need for crop production in this state.

ZINC: In Minnesota, there is a more widespread need for this micronutrient than any other. When soil test levels are low, corn and edible beans are the only two crops that respond to the addition of zinc in a fertilizer program. Zinc suggestion for these two crops are listed in the following table.

Zinc guidelines for corn and edible beans in Minnesota.

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ppm zn broadcast or band

0.0 to 0.25 10 2

0.26 to 0.50 10 2

0.51 to 0.75 5 1

0.76 to 1.00 0 0

1.00+ 0 0

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When I checked on prices with the local fertilizer dealer, the cost of zinc in dry form was about $1.50 per pound of zinc. Cost will be higher if applied as a fluid source. So, application in a band can reduce fertilizer cost substantially. However, research has shown that a pound of zinc is a pound of zinc. In other words, a pound of actual zinc as a dry material is just as effective as a pound of zinc is a liquid formulation.

The exact role of zinc in plants has not been clearly defined. It is necessary for the functioning of several enzymes. When deficient, there is not normal growth and development.

MANGANESE: Like zinc, manganese is essential for many ensyme reactions in plants with no specific, well-defined function. The use of this micronutrient HAS NOT increased crop production in Minnesota. Specifically, manganese has been applied to soybeans in field trials–especially glyphosate tolerant soybeans. Although reports from other states have indicated that there is a response in these situations, these responses have not been measured in Minnesota.

IRON: Many soybean growers are familiar with Iron Deficiency Chlorosis (IDC) in soybeans. There is no deficiency of iron in Minnesota soils. Under certain conditions, the iron cannot get into the plant or is not used in the plant in the production of chlorophyll. This condition is made worse by high levels of nitrate-nitrogen in the soil. Foliar application of iron does not work consistently. A product called SOYGREEN applied with the seed at planting time in combination with a small grain competition crop will help to overcome the problem.

COPPER: Small grains grown on organic soils in northern Minnesota have shown a positive response to the application of this micronutrient. Otherwise, there is no need for this micronutrient in a fertilizer program.

BORON: There is no universal agreement as to the role of this micronutrient in plants. Yet it is still essential. In Minnesota, ther have been occasional increases in the yield of alfalfa if soil tests show that there is a need and this micronutrient is applied. A topdress application of 2 to 4 pounds of actual boron per acre is suggested if the soil test shows that there is a need. Be careful with this micronutrient. Applications, when not needed, can reduce yield.

CHLORIDE: Although the specific function in plants is not known, this micronutrient can resist disease pressure in small grains if it is deficient. This micronutrient is not needed in a fertilizer program if 0-0-60 has been used in the past. That’s nearly all of Minnesota.

Recently, there have been some sales promotions which claim that micronutrients coated or sprayed on other fertilizer granules will improve crop yields. These are bogus claims that are not substantiated by research. No matter how you shake it, bake it, slice it, or dice it, if a micronutrient does not increase yield (production) it is not needed. Use of micronutrients in situations other than those described in the previous paragraphs is purely recreational—–and expensive.