SP645-When Are Micronutrients Needed for Farm Fields

This factsheet provides a listing of secondary and micronutrient soil tests available through the University of Tennessee Soil Testing Laboratory in Nashville. It also summarizes all of the university’s secondary and micronutrient recommendations and guidelines based on current research. Some recommendations are based upon soil test values (Table 1) interpreted as either satisfactory (levels adequate for excellent crop production) or unsatisfactory (levels indicating a need for fertilization). For other micronutrients, such as boron or molybdenum, a general recommendation is made for those crops observed to respond consistently to such fertilization. For copper, the soil test is currently only used to monitor changes in soil copper levels.

A general discussion is provided for sulfur, as it is often included in fertilizer blends, but seldom increases yield in Tennessee. A weak acid extractant called Mehlich 1 is used by the University of Tennessee to test soils for nutrient levels. Critical micronutrient soil test values listed in this factsheet are only valid when the laboratory testing your soil uses the Mehlich 1 soil test.