Miller Calls for Caution on "Micro-Nutrient" Fertilizers

"Farmers need to know that their soils will seldom need additional micro-nutrients," Miller said. "We have surveyed the literature and consulted with experts at Iowa State, and the general conclusion is that Iowa soils naturally contain sufficient levels of these nutrients."

"Deficiencies occur only occasionally, but they will be shown by symptoms on the plants themselves and they can be remedied by application at that time," he said. "It is very unusual that farmers need to add soil micro-nutrients before they put in a crop."

Iowa farmers typically make substantial purchases of primary soil nutrients such as nitrogen, phosphorus and potassium. Miller said soil "micro-nutrients" include iron, copper, zinc, boron, manganese and molybdenum.

"Based on IDALS Fertilizer Bureau sales records and sample price lists, we estimate that over $8 million of soil micro-nutrients were sold last year in Iowa," Miller said. "It's a significant sum."

"Our advice to farmers is that, unless deficiency symptoms appear in plants, the application of soil micro-nutrients is rarely justified economically in Iowa," he said. "We encourage farmers to ask for specific research and justification if an input supplier recommends the use of micro-nutrients."

"Our advice to those who sell inputs is to be sure their representations are accurate, and that they be careful not to exaggerate the usefulness of micro-nutrients in improving yield or profitability."

Miller emphasized that input sellers may sell micro-nutrient inputs to farmers, and that some farmers may choose to experiment with them in hopes of improving their crops. He said new research is being done with new hybrids and various environmental conditions and that micro-nutrients might be useful in the future. But Miller said current research doesn't indicate that improvement is likely today in most cases. He said input sellers must be careful not to misrepresent the nutrients beyond what is justified by expert studies.