Michigan State University Extension
Soils & Soil Management - Fertilizer - 05209711
07/10/97
Secondary and Micronutrients for Vegetables and Field Crops Extension Bulletin E-486, Revised August 1994
By M.L. Vitosh, D.D. Warncke and R.E. Lucas Department of Crop and Soil Sciences Michigan State University Extension
Nutrients can be absorbed through plant leaves. In some situations, foliar-applied micronutrients are more readily available to the plant than soil-applied micronutrients, but foliar applications do not provide continuous nutrition as do soil applications. Foliar spray programs may be used to supplement soil applications of fertilizer or to correct deficiencies that develop in mid-season.
When spray equipment is available, secondary and micronutrient needs of plants may be met with a good spray program. Suggested secondary and micronutrient sources and spray rates per acre are given in (Vis. 32). Use low rates for young plants and high rates when plants develop dense foliage.
Micronutrient chelates are generally no more effective than water-soluble inorganic sources when foliar applied. Chelates, however, are more compatible when mixed with other spray materials.
For a preventive spray program, spray the crop about four weeks after emergence or transplanting. Because many micronutrients are not readily translocated within the plant, a second spray will be needed two weeks later to cover the new foliage. When a known nutrient deficiency develops, spray the crop with the appropriate nutrient at the recommended rate every 10 days until the deficiency is corrected. Complete coverage of the foliage is important, especially for iron. Adding a wetting agent to the spray solution will improve the coverage and may increase absorption, especially in crops with waxy surfaces, such as cauliflower and onions. Micronutrients may be mixed with most fungicides and insecticides. However, some combinations are incompatible and may injure crops. When in doubt, spray only a limited acreage until compatibility is established. Any injury will usually appear within 48 hours. (Vis. 33) provides a guide for obtaining the desired mixture of various secondary and micronutrient carriers.
In developing a spray program, remember that some fungicides and insecticides contain copper, manganese or zinc. The amounts of micronutrients present in these materials may or may not be sufficient to correct a deficiency but should be considered when determining a spray program.
| Visual title - Visual size | Visual title - Visual size |
|---|---|
| Suggested rates and sources of secondary and micronutrients - 27K | Pounds of secondary or micronutrient carrier needed to obtain the - 38K |
