For all crops, micronutrients are equally as vital as the primary NPK (Nitrogen, Phosphorus, & Potassium) plant foods. The only difference is the amount; plants need relatively small quantities of micronutrients. The quantity of a micronutrient that a particular crop will require varies. Corn will require nitrogen and zinc in the ratio of about 100 to 1. But, the lack of zinc can make the difference between a 100-bushel per acre harvest and a crop failure. The deficiency of one or more micronutrients or secondary nutrients, can be very costly in the long run.
| Micronutrients | Functions Within the Plant | Soil Type and Condition Where Deficiency May Occur | Crop Most Susceptible to Nutrient Deficiency |
|---|---|---|---|
| Boron (B) | Essential to actively growing tissue in the new growth; necessary for pollen viability and good seed set. | Occurs in acid-leached soils, coarse textured sand soils, peats and mucks, drought conditions, overlimed soils, alkaline or low organic matter soils. | Alfalfa, apples, beets, citrus, clovers, cotton, cauliflower, cabbage, celery, corn, sweet potatoes, tomatoes, tree crops, sugar beets, and tobacco. |
| Copper (Cu) | A major part of necessary photosynthesis enzyme. Very important during the plant's reproduction stage. | Occurs in sandy soils, peats and mucks, overlimed soils, and in high concentrations of iron and manganese. | Small grains, corn, vegetables, tree fruits, wheat, carrots, and onions. |
| Iron (Fe) | Promotes formation of chlorophyll. | Occurs in alkaline soils, in calcareous soils when cold and wet, in soils where phosphate has been excessively applied. | Beans, soybeans, corn, sorghum, tree fruits, ornamentals, grasses, milo, lemons, limes, and rice. |
| Manganese |
A part of important enzymes involved in respiration and Protein synthesis. | Occurs in acid soils (low pH) and in highly-weathered acid leached soils, and in soils with low Phosphate levels. | Soybeans, small grains, tree fruits, cotton, leafy vegetables, dry beans, and sugar beets. |
| Molybdenum (Mo) | Essential for nitrogen fixation by nodule bacteria in legumes. Essential for nitrogen redustase performance nitrate to amine form. | Occurs in acid soils (low pH) and in highly-weathered acid leached soils, and in soils with low Phosphate levels. | Cauliflower, citrus, tobacco, and all legumes. |
| Zinc (Zn) | Important as a catalyst for growth regulators in plants and the use of other nutrients. Affects maturity. | Occurs in calcareous soils (pH of 6.0 or above) after leaching and erosion; in acid leached soils; in coarse sands; and in soils where Phosphate has been excessively applied. Also in low organic matter, or overlimed soils. | Beans, soybeans, citrus, corn, sorghum, onions, potatoes, tree fruits, flax, sugar beets, wheat, cotton, milo, rice, and sweet corn. |
| Calcium (Ca) | A secondary nutrient found in greatest amount in cell walls. Utilized in cell division and involved in nitrogen metabolism. | Occurs in low pH soils. Also in areas of high nitrogen applications and hig hpotassium levels, particularly prevalent in the uploand soils of the old cotton belt areas. | Alfalfa, vegetable crops, tree fruits, cotton, potatoes, tomatoes, sugar beets, celery, citrus, soybeans, and other legumes. |
| Magnesium (Mg) | A secondary nutrient and is a part of chlorophyll. Participates in the activity of enzymes. Assists in translocation of phosphorus in the plant. | Occurs in low pH soils. Also in soils where excessive potash has been applied, or in areas of high calcium-lime use. | Cotton, cabbage, rots, celery, corn, cucumbers, melons, squash, snapbeans, tree fruits, small grains, onions, potatoes, tobacco, sugar cane, tomatoes, turnips, corn, and citrus. |