Olga S. Walsh, Cropping Systems Agronomist, UI Parma, and Eva Nambi, Post-Doctoral Fellow, UI Parma
Micronutrients are essential elements that are used by plants in small quantities. Critical plant functions are limited if micronutrients are unavailable, resulting in plant abnormalities, reduced growth and lower yield. In such cases, expensive, high requirement crop inputs such as nitrogen (N) and water may be wasted because they may not be the yield-limiting factors. On the other hand, micronutrients may be yield-limiting for various reasons, such as being unavailable due to soil pH and other micro environmental problems in the soil. N use efficiency is affected by the availability of other plant nutrients. Sulfur is a critical component of amino acids and are the building blocks of protein. Sulfur is essential for chlorophyll formation and is important in plant N metabolism. In soils, the majority of S is contained within soil OM, in a form unavailable to plants. Plant-available S is released to soil solution via mineralization.
Most soils within the Snake River Plain are adequate in S, and irrigation water often contains substantial S levels. However, with soils containing < 10 ppm S, and low-S irrigation water, a 20 to 40 lb per ac of S may result in positive wheat yield response. Furthermore, grain quality in hard wheat varieties is a function of both N and S. In production of wheat, which is not a cash crop in most parts of southeastern Idaho, it is especially important to maximize the efficiency of all agricultural inputs, due to lower return on investment. Very little new research has been done on micronutrient and S response since mid-1980s; our proposal is extremely timely. Routine soil testing at Parma R&E Center showed that many fields in Parma area may be low in several micronutrients. On the other hand, it is not uncommon to see wheat response to micronutrients and S even for fields not identified as micronutrient deficient. Furthermore, interactions of N, micronutrients, and S (synergistic or antagonistic effect) is an important factor to be considered.
Field experiments were conducted at Parma R&E Center. We focused on the hard white winter wheat in view of recent market opportunities for wheat with higher protein content and better quality of protein for baking and noodles. The field trials enabled us to assess combinations of micronutrients (Fe, B, Zn, Mn) and sulfur (S) applied at three rates (low, medium, and high) and two application methods/times (soil applied at planting, and foliar applied at tillering). A no-micronutrient check will be established as a benchmark to assess wheat response to applied micronutrients.
Parma 2021 growing season results indicated that:
- Although yield differences among Fe treatments were not statistically significant, Fe applied at medium and high rates at tillering appeared to be most beneficial.
- Although yield differences among B treatments were not statistically significant, B applied at tillering resulted in numerically greater yields.
- Application of Zn improved wheat yields, especially when applied at tillering, however the differences among Zn-fertilized treatments were not statistically significant.
- Application of Mn at planting, especially at low rate, was associated with higher yields. Medium and high rates at planting or at tillering did not further improve yields.
- Application of S resulted in highest yields in Parma 2021 field trial. Sulfur fertilization at planting appeared most beneficial.
We plan to include this information into updated wheat production guides along with new information on nutrient application rates for wheat grown in Idaho.
PREVIOUS GREENHOUSE TRIAL
OBJECTIVES:
1) To assess the response of winter wheat to four micronutrients (Fe, B, Zn, and Mn ) applied at three rates (low, medium, and high), and two application methods/times (soil applied at planting, and foliar applied at tillering) and quantify its’ pattern throughout the growing season,
2) To explore the potential of using handheld spectroradiometer (ASD FieldSpec 4) to estimate wheat grain yield, quality, and macronutrient and micronutrient content of the grain.
Preliminary greenhouse trial results:
· application of Fe to the soil at planting (especially at high rate) increased wheat yield
· application of Zn to the soil and planting and foliar at tillering (especially at medium rate) increased wheat yield
· application of B to the soil at planting (especially at medium rate) slightly increased wheat yield
· wheat yields had a mild positive response to application of Mn to the soil at tillering, but application of Mn at tillering foliar substantially reduced whet yields at all application rates
· application of S (all methods/times and rates) reduced wheat yield.
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