Micronutrient decisions for field crops

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.        

Are supplemental micronutrients needed in field crop production? In Michigan boron (B), manganese (Mn), and zinc (Zn) are the ones of most importance. There is good information about micronutrient needs for Michigan in MSU Extension bulletins E-486 and E-2904. There are a number of ways to determine whether or not certain of the micronutrients are needed. Knowing the responsiveness of the crop being grown to these micronutrients and the soil conditions where a deficiency is likely to occur can be helpful. Table 1 presents selected information.

Manganese availability is closely related to the degree of soil acidity. Deficiency is more likely to occur on slightly acid (pH 6.6 to 7.0) or alkaline (pH > 7.0), such as lake bed soils, glacial outwash soils and muck soils. Acid soils that have been limed are more likely to be Mn deficient than naturally neutral or alkaline soils. It is difficult to buildup up residual levels of available Mn in soil, therefore if Mn deficiency occurs on a responsive crop one year it will likely occur on responsive crops in subsequent years unless Mn is applied. Hence, good observations of the crop health is important.

Zinc deficiency is more likely to occur on soils with a neutral to alkaline reaction. Wet cool weather in early spring may increase the likelihood of Zn deficiency. High levels of applied or available soil phosphorus may increase the chance for Zn deficiency in responsive crops. Residual levels of available soil Zn can be built up by application.

Boron deficiency is more likely to occur on sandy soils because B being mobile in the soil is more likely to leach out of these soils. Also, adequate soil moisture is important for movement of B to plant roots. Droughty soil conditions increase the chance of B deficiency in responsive crops. In clay textured soils soil moisture conditions are better and B is less likely to be leached out.

Copper deficiency may occur on small grains grown on high organic soils (> 10 %), such as organic sands. Most mineral soils in Michigan contain adequate available soil copper.

Soil and plant tissue tests are good tools to use to determine the need for supplemental amounts of key micronutrients. Plant tissue analysis is frequently used for trouble shooting plant growth problems, but it can also be very useful for evaluating a soil fertility program. Plant tissue analysis is useful for developing long-term soil fertility programs, including the need for micronutrients.

Table 1. Responsiveness of select field crops to B, Mn,
Zn and Cu when the available level in the soil is low.

Crop

B

Mn

Zn

Cu

Alfalfa 

H

L

L

M

Beans, dry

L

H

H

L

Bromegrass

L

M

L

L

Corn    

L

M

H

M

Soybean

L

H

M

L

Sugar beets

M

H

M

M

Wheat

L

H

L

H

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