AMES, Iowa – Micronutrients may be found in small amounts in the soil but they play a huge role in plant growth and development. In fact, most micronutrients in the soil are involved in critical enzymatic reactions such as photosynthesis and respiration.
These micronutrients, and their function in the soil, is the subject of a new Iowa State University Extension and Outreach publication titled "Suggested soil micronutrient levels and sampling procedures for vegetable crops" (HORT 3063).
The publication was written by Ajay Nair, assistant professor of horticulture and extension vegetable production specialist at Iowa State University.
“Generally Iowa’s soils are very productive and have sufficient amounts of nutrients for healthy crops to grow,” Nair said. “It’s not often that we think about micronutrients in the soil, because we don’t often see a shortage in our plants because the soil is so good. However, that doesn’t mean deficiencies can’t show up.”
Regular soil testing is important to maintain a proper nutrient management plan. These tests should be done yearly to provide information on nutrient concentration, pH, soil organic matter and salinity.
“Regular soil testing is critical,” Nair said. “We recommend one test per year and prefer it be done in the fall. If the sample is taken in the fall then there is time to take corrective measures in the fall for optimum soil nutrient levels in the spring. While soil tests should be run yearly, testing specifically for micronutrients should be done every four to five years.”
The publication also includes a table with information on six different micronutrients and their roles in plants, deficiencies and what happens when there is an excess of that nutrient.
There is also information on proper techniques for obtaining leaf samples of common vegetable plants for nutrient testing.
“Deficiencies show up in different areas of the plant, sometimes in the upper leaves or the lower leaves depending on the type of nutrient,” Nair said. “Sending tissue showing the deficiency isn’t enough. We need to be able to compare it with something that is healthy in that field so we can have a baseline to test the deficient leaves against.”
ISU’s Soil and Plant Analysis Laboratory provides cost-effective analytical testing and research-based limestone and fertilizer recommendations to support sustainable management decisions. The laboratory provides soil, plant, water and environmental testing services and can be contacted at 515-294-5567 or soiltest@iastate.edu.