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Microsource Minute

Evaluating Micronutrient Levels / Right Rate

 

Soil testing is a necessary tool for nutrient assessment in order to improve soil and crop performance.  Regular soil testing is recommended in order to determine the Right Rate for macro and micronutrients.  Zinc, boron, manganese, iron, and copper are the five micronutrients of concern in crop production.  Although these elements are required in small amounts, their deficiency can have as much effect on crop production as any of the major nutrients. 

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When evaluating soil test results, remember to study all soil characteristics. Soil type, pH, organic matter, nutrient interactions (excess of some nutrients limits availability of others) and past management all should be considered.

Soil factors that affect availability:

  • Zinc:  low OM, high pH. Excessively high P (common in soils that have had repeated manure applications). Cold, wet soil, cloudy (low light)

  • Boron:  course textured, highly leached soils (sand). Low OM, high soil pH. High available soil Ca. Dry weather (lack of organic matter mineralization)

  • Manganese:  insoluble at high pH. Excessive P, Ca, Zn, Fe or Cu can reduce availability.  High OM (Mn adsorption onto soil organic matter), compacted soils.

  • Iron:  high soil pH, low soil OM. High Cu and Mn. Excessive water.

  • Copper:  course textured, highly leached soils.  High OM soils, high soil pH. High available soil Zn, Fe and P.

*Proper pH management is most critical to micronutrient management

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Soil sampling is essential to determine how much of a nutrient is currently available in the soil.  However, application rates should not be determined from that alone.  Crop type, management techniques, climate, and fertilizer source all play a critical role.  Tissue sampling is also recommended as a supplementary tool to asses nutrient needs.

 

Author: Ethan Enochs

 
Ethan Enochs