This NCERA-103 committee bulletin (NDSU Extension, revised 2025) evaluates the effectiveness of applying plant nutrients at low rates (below crop removal or below university-recommended rates), including micronutrients. Fourteen essential mineral nutrients are listed with typical concentrations in North Central Region crops (Table 1), giving reference values for B, Cu, Fe, Mn, Zn, and Mo in corn grain/stover and soybean seed/straw (e.g., corn grain: B 70 ppm, Cu 25 ppm, Fe 36 ppm, Mn 24 ppm, Zn 18 ppm, Mo 0.09 ppm; soybean seed: B 28 ppm, Cu 8 ppm, Fe 80 ppm, Mn 22 ppm, Zn 50 ppm, Mo 0.16 ppm).

The document's detailed low-rate starter fertilizer research for corn and soybean focuses almost entirely on nitrogen, phosphorus, and potassium rather than micronutrients; no specific micronutrient rate trials for corn or soybean are reported in the text. Micronutrients are mentioned conceptually: crop removal of most micronutrients is small, and unlike P/K (which require ongoing fertilization due to large removal) or Ca/Mg (replaced via liming), only certain crop-nutrient combinations have consistently low soil supply requiring micronutrient fertilization -- though the bulletin does not identify specific corn/soybean cases needing supplementation.

For soybean specifically, the bulletin notes that foliar micronutrient fertilization (including S, Fe, B, and Zn) was tested across 18 sites in Iowa research and produced only a "similarly low positive response rate" to earlier single-nutrient foliar trials. The overall conclusion for the region is that using low rates of nutrients, including via foliar application, has not been consistently effective at increasing yield, crop quality, or profitability, and foliar micronutrient application may be best reserved for situations where soil application would be ineffective.