In Minnesota, the importance of nitrogen as well as phosphate and potash in a fertilizer program for hard red spring wheat production has been demonstrated in various trials conducted throughout the northwest region of the state. Evaluation of the importance of sulfur and the micronutrients (zinc iron, copper, manganese) has been limited. In recent years, there have been several marketing claims that the application of various micronutrient combinations would increase the yield and grain protein content of hard red spring wheat. Therefore, trials were conducted in 2005 in an effort to evaluate these claims.

Three locations were used. The results of analysis of soil samples collected before fertilizer application are listed in Table 1. Soil pH, phosphorus (P), and potassium (K) values were typical of many soils used for spring wheat production in northwest Minnesota. The values for the extractable micronutrients varied somewhat from site to site. The relative categories for the micronutrients are not defined because responses to micronutrients for the mineral soils of Minnesota are not known.

Table 1. Relevant soil properties for the experimental sites.

Adequate amounts of nitrogen, phosphate, and potash were broadcast and incorporated before planting. The rates of these nutrients applied to all treatments were based on an expected yield of 60 bu. per acre.

Various combinations of four micronutrients (iron, copper, manganese, zinc) were either broadcast and incorporated before planting or applied as a foliar treatment with a surfactant. When soil applied, the rate was 5.0 of the micronutrient used per acre. When applied as a foliar treatment, the rate was 0.5 lb. of the micronutrient per acre. The dry, granular sulfates were used for the broadcast application. The chelated materials were used for the foliar treatments.

The impact of the various micronutrients was determined by evaluating grain yield (corrected to 13.5% moisture) and grain protein.

The impact of micronutrients on wheat yield is summarized in Tables 2 and 3. With the treatments used in this study, a micronutrient would be considered to be important for production if either yield or protein decreased when the micronutrient was removed from the fertilizer program.

Table 2. Yield of hard red spring wheat as affected by the broadcast application of micronutrients.

Table 3. Yield of hard red spring wheat as affected by the foliar application of micronutrients.

Considering the broadcast applications (Table 2), the results were consistent. Yields at all sites were not reduced when a micronutrient was not included in the fertilizer program. There were differences in yield averages at all sites. However, these differences were not statistically significant. Therefore, it’s possible to conclude that the treatment used had no effect on yield.

In evaluating the effect of foliar applications (Table 3), grain yields were reduced when zinc was not included along with the other micronutrients. From visual observation, it was obvious that there was severe leaf burn for the treatment where zinc was not used, but the other micronutrients were applied. The reduction in yield is attributed to the leaf burn. There is no obvious explanation for the burn in only one treatment.

At two of the three locations (West Ottertail Co, NWROC), yields were higher for the treatments where the micronutrients were broadcast. The yields of all treatments were averaged to reach this conclusion. This information would indicate that there was leaf burn or some other negative factor associated with the foliar application of micronutrients.

When yields from all sites are evaluated and the factor of leaf burn is removed from consideration (broadcast treatments), there was no reduction in production when any of the four micronutrients was not included in the fertilizer program. Therefore, there is no indication that use of micronutrients is important for hard red spring wheat production on soils that are representative of those in northwest Minnesota. This is especially true if a foliar application of micronutrients is being considered.

The impact of micronutrient use on the protein content of spring wheat is summarized in Tables 4 and 5.

Table 4. Protein content of hard red spring wheat as affected by the broadcast application of micronutrients.

Table 5. Protein content of hard red spring wheat as affected by the foliar application of micronutrients.

Protein content varied with location. At this point, there is no apparent explanation for the lower percentages at the Red Lake County site and the higher percentages at the Northwest Research and Outreach Center (NWROC).

The protein content was not affected when any of the micronutrients studied was not included in a fertilizer program. Considering both grain yield and protein content, there appears to be no justification for including micronutrients in a fertilizer program for hard red spring wheat production.

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