Ontario Corn and Soybean Micronutrients Knowledge Hub

Water-logging and the inability to take up sufficient iron (Fe), causing iron deficiency chlorosis (IDC) in soybean (Glycine max, L. Merr.), can be major yield reducing factors in certain soils in the northern USA and Manitoba, Canada, soybean growing regions. The objective of this research was to evaluate soybean IDC, biomass production, and yield with seeding on raised beds and seed application of the Fe-chelate compound ortho-ortho-Fe-EDDHA. In six environments, soybean were seeded on raised beds and conventionally prepared seedbeds (flat) and with a factorial arrangement of five cultivars (within adapted maturity group 0.1 to 0.9 and variable IDC tolerance) and seed applied Fe-EDDHA using rates of 0 kg.ha-1 and 3.36 kg.ha-1. There were no significant interactions between the factors tested. The plant population was 27% higher on the raised beds compared with flat, and yield was 6.3% higher (2893 kg.ha-1 vs. 2722 kg.ha-1). Total dry plant biomass on raised beds was 9.8% greater compared with flat. The plant population with seed applied Fe-EDDHA was 10.6% lower compared with no application. However, the IDC score was significantly lower 2.2 vs 2.4 (1 = green, 5 = dead) for Fe-EDDHA seed application. Yield and plant biomass were not significantly different between Fe treatments. Raised beds offer an opportunity for soybean growers to reduce the negative influence of excessive water. Further research is needed to determine the long-term effect of raised beds on plant development, IDC expression, and yield. The application of Fe-EDDHA remains a partial solution and should therefore be combined with other methods to reduce IDC. Further research should study other Fe-EDDHA application rates and methods.

This NDSU bulletin (SF882) provides soil-test-based fertilizer recommendation tables; its micronutrient section covers zinc (Zn), iron (Fe), manganese (Mn), copper (Cu), and boron (B), analyzed by DTPA (or hot water for B) soil tests. Zinc calibration in North Dakota applies only to corn, potato, flax, and dry edible bean, NOT soybean. For corn testing low to very low in Zn (DTPA categories: very low 0-0.25, low 0.26-0.50, medium 0.51-0.75, high 0.76-1.00, very high 1.01+ ppm), the recommendation is 10 lb Zn/acre as broadcast zinc sulfate, or one-third that rate seed-placed/near-seed banded; Zn need is greater when high broadcast or starter phosphorus is applied. A broadcast zinc sulfate application is expected to correct deficiency for 4-5 years; banded chelates (1 pint-2 quarts/acre) and foliar zinc chelate sprays are also effective for single-season correction. No Zn is recommended on medium-or-above-testing fields. Iron deficiency chlorosis (IDC) is identified as a serious problem specifically in soybean (also flax, field pea, dry bean), driven by soil carbonates, wetness, cold soils, and high soluble salts; most other ND crops are not iron-sensitive. The most consistent soybean yield response comes from seed-placed ortho-ortho-FeEDDHA (or newer FeHBED) chelate applied in-furrow; foliar iron sprays are not effective for correcting IDC. For manganese and boron, the bulletin states no confirmed field deficiencies or documented yield responses in North Dakota, so no soil-test-based recommendation is made for either nutrient (categories listed as "no categories"/not established) ? manganese solubility increases sharply below pH 5, with manganese toxicity in canola observed near pH 4.5. For copper, calibration only applies to wheat/durum and barley on low-organic-matter (<2.5%), sandy soils with low Cu (<0.3 ppm); even then only about 15% of applications show a positive yield response, so copper use is generally not economically favorable. No corn- or soybean-specific copper or boron recommendation is provided.

This NDSU soybean production field guide (A1172) identifies iron deficiency chlorosis (IDC) as the major soybean micronutrient problem in the state, especially in eastern North Dakota where high rainfall and surface calcium carbonate reduce iron availability; IDC in early vegetative stages can severely reduce yield. The primary management strategy is planting IDC-tolerant cultivars, selected using NDSU's annually updated soybean variety trial IDC ratings. For chemical correction, foliar iron sprays are described as ineffective; the most effective treatment is in-furrow, seed-placed ortho-ortho-EDDHA iron chelate applied with water at seeding, because this specific isomer can deliver iron to roots and then return to the soil solution to capture and redeliver additional iron throughout the season. Response is directly proportional to the percentage of ortho-ortho (versus ortho-para) EDDHA in the product, so product chemistry matters. A five-point IDC management strategy for fields with surface pH greater than 7 is given: (1) use field history/soil testing to avoid fields with high surface carbonates and soluble-salt EC above 2 mmohs/cm; (2) select high-IDC-tolerance cultivars from NDSU trial data; (3) seed a companion small-grain crop (oats, barley, or spring wheat) at planting, particularly when soil nitrate-N exceeds 80 lb N/acre; (4) apply a high-ortho-ortho-EDDHA iron fertilizer in-furrow at seeding at recommended rates; (5) where possible, choose herbicides with low soybean phytotoxicity, though weed control takes priority if weed pressure is high. The guide explicitly states that soybean deficiencies of zinc, manganese, boron, molybdenum, nickel, chloride, and copper have not been observed in North Dakota, and there is no need to apply any of these nutrients to North Dakota soybean fields. Soybean is also noted as highly sensitive to salt-affected soils, with cultivar salt tolerance roughly correlated to IDC tolerance.

Foliar fertilization is an effective practice that improves both the yield and quality of maize, a crop with high and specific micronutrient demands. This study hypothesized that foliar application of Fe, Cu, Mn, Mo, Zn and B would improve grain size and quality in GS210 maize compared to the control. The single-factor field experiment was conducted in 2023?2024 on Haplic Cambisol (Eutric) soil, under a variety of meteorological conditions. The application of Zn and B fertilizers significantly increased the soil plant analysis development (SPAD) index. Yield components (number of grains per ear, thousand-grain weight) and grain yield increased significantly following Zn foliar application compared to the control. Zn application increased grain yield by 0.59 t ha-1 and 0.49 t ha-1 in 2023 and 2024, respectively. Smaller but beneficial effects were observed with Cu and B applications. In contrast, the effects of fertilization with other micronutrients (Fe, Mn, Mo) were less pronounced than anticipated. Biochemical analyses revealed that foliar fertilization with Fe, Cu and Mo increased total phenolic content and antioxidant capacity, while Fe and Mo enhanced carotenoid accumulation, and Cu and B significantly influenced grain color parameters. The study highlights the potential of foliar fertilization to improve maize performance and grain quality, despite possible antagonisms between micronutrients.

Chloride is a micronutrient required for photosynthesis but when applied in the concentration of a macronutrient, it may also promote growth by regulating turgor. However, if chloride accumulates excessively, it can induce toxicity. The aim of this study was to identify physiological dysfunctions in maize (Zea mays L.) that arise in response to excessive chloride ion accumulation. For this, a novel water sensor was employed for the first time allowing the in vivo measurement of water content in the plant by using two near IR-wavelengths with different absorption of water. This enabled to analyse whether water imbalances occurred. Chloride was given together with calcium as companying counter cation. Results show that most of the tested maize genotypes were able to maintain growth, photosynthesis and normal water content when stressed with concentrations as high as 757.1 mg chloride/kg soil dry matter. Leaf blades accumulated only 8.5 mg chloride/g dry matter, with the most genotypes not even showing salt stress necrosis at the leaves. A comparison between more tolerant and more sensitive genotypes revealed that restriction of chloride root-to-shoot translocation is a trait of chloride tolerance.

Mineral nutrients, such as zinc (Zn), are critical for plant growth; however, the effect of Zn on insect herbivory is poorly characterized. Because Zn deficiency may compromise plant physiology while high levels of zinc may be directly toxic to herbivores, we predicted lepidopteran herbivores would perform best on plants deficient in Zn or those with an intermediate dose of Zn fertilizer. We first tested these hypotheses in a greenhouse experiment using maize (Zea mays L. [Poaceae]) and two noctuid caterpillars, Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae) and Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) and evaluated the effects of a normal range of Zn (0-11.7 g m-3) on the interaction between maize and each caterpillar species. In the greenhouse, we found Zn increased uptake of other nutrients, particularly nitrogen (N), and fertilizing with just 2.5 g m-3 Zn maximized maize growth. Spodoptera frugiperda performance increased marginally with Zn fertilization. While neither caterpillar species was directly affected by Zn concentrations in leaves, S. frugiperda caterpillars responded to leaf N. In the field, we investigated the effect of Zn fertilization on leaf-nutrient concentrations, early season damage by resident herbivores, performance of S. frugiperda on excised leaf tissue, and maize yield. We found fertilizing with Zn increased leaf N, but compared to the greenhouse experiment, had a smaller effect on Zn uptake and no effect on herbivory. Zinc treatments did not affect maize yield in the field. We conclude that Zn fertilization can increase N leaf concentrations, which in turn can affect some herbivores, with species-specific effects.