A regional publication will be available in both web page and printed format. This will be the first regional publication with a thorough discussion of micronutrient needs for soybean based on recent information from the North Central region. The publication will discuss soybean need for micronutrients, factors that influence micronutrient utilization, and the value of soil and plant tissue testing to diagnose sufficiency levels and decide fertilization needs. The summarized information along with the publication general recommendations will be useful to farmers and consultants across the region. The paper and information also will be useful in developing future specific guidelines of each state or sub-regions. All co-investigators have research and extension appointments, and have co-responsibility for establishing and explaining nutrient management guidelines for soybean. Often they are consulted by growers and crop consultants. In addition, several team members represent their states at the North Central Soil and Plant Analysis Committee (NCERA-13), which proposes regional guidelines for soil and plant testing methods. Synergies generated from this work will not only allow for the completion of the objectives in this proposal, but also will result in other opportunities for collaboration on soybean fertility research across state lines.

No specific final results are possible for this type of project. Information collected up to this time is confirming that the likelihood of soybean yield response to micronutrients is small across the entire region, and that use of sufficiency levels for soil or plant-tissue tests being suggested in the literature for most micronutrients or soybean yield levels may encourage unneeded fertilization. However, deficiencies and likely response to fertilization are observed in some specific soil types or conditions found in smaller areas. Deficiencies of several micronutrients are commonly observed in sandy, coarse textured soils. Soybean iron deficiency chlorosis (IDC) is frequently observed in high-pH (calcareous) soils in the western area of the region, and recent research being summarized shows that newly available products and methods of application have good potential to alleviate deficiencies. Manganese deficiency in soybean sometimes is observed in northcentral region states east of Illinois and Wisconsin. However, the information collected indicates the challenge of identifying specific responsive fields by soil or tissue testing given significant impacts of transient and temporally variable soil properties such as moisture and aeration on Mn plant-availability. The information available shows that high yielding soybean can remove high amounts of micronutrients with harvested grain, but that the yield level or the yield potential alone cannot be used as indicator for micronutrient fertilizer requirements. Therefore, major concepts likely to be included in the publication will be the inadequacy of published sufficiency levels for some micronutrients for soil or tissue tests, the poor reliability of tests for other micronutrients, and a need for further research focusing on specific soils or conditions where yield response is most likely. These include sandy, calcareous, organic, or severely eroded soils.