by Antonio Mallarino, Soybean Agronomist, Iowa State University
My colleagues and I receive many questions about potential yield loss due to micronutrient deficiency, especially given the number of product options and decreasing margins. We recognize the frustration of growers and crop consultants with the lack of publications that address micronutrient issues.
Over the past year, with funding from the North Central Soybean Research Program, a team of agronomists from five north-central states have collected and analyzed all of the published and unpublished university field response-based information about micronutrients and soybeans in the region, including soil and plant tissue analyses. We plan to summarize this information in a comprehensive publication to be distributed widely in the fall of 2016.
The information collected up to this time confirms a small likelihood of yield response to micronutrient application. We are also finding that soil and plant tissue tests suggested by most micronutrient literature can lead to excessive and unnecessary fertilization.
However, micronutrient deficiencies have been observed in specific soil types or conditions such as 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 shows that some available products and methods of application have good potential to alleviate deficiencies.
Manganese deficiency in soybean is occasionally observed in states east of Illinois and Wisconsin. However, the information collected indicates the challenge of identifying specific responsive fields by soil or tissue testing because of the significant impact of transient and temporally variable soil properties such as moisture and aeration on plant-available manganese.
The publication will include a thorough discussion of soybean micronutrient needs, micronutrient utilization, and soil and plant tissue testing to diagnose micronutrient sufficiency levels. We hope the publication will empower Midwest farmers with the information they need to make sound decisions for their production system.