Ontario Corn and Soybean Micronutrients Knowledge Hub

A field experiment was conducted in 2015-2017, in the Production and Experimental Station located in Balcyny (51.6667 degrees N, 18.1667 degrees E). The surface area of a plot for harvest was 450 m(2). The following nitrogen fertilizers were applied in the experiment: UAN - 32%N, UAN+S - 26% N + 3% S, UAN+P (medium) - 26% N and 11% P2O5, UAN+P (starter) - 21% N and 18% P2O5, UAN+Mg - 20% N + 4% Mg. It has been demonstrated that the content of micronutrients in maize grain is modified more by the atmospheric conditions (year of cultivation) than by the tested fertilization. The highest content of Zn, Mn and B was determined in the grain harvested in the second year of the experiment, when total rainfall was slightly higher than the long-term average. In turn, when the rainfall was deficient in the first year, maize contained the highest levels of Cu and Fe. Fertilization had no effect on the content of copper and manganese in grain, while nitrogen fertilization lowered the content of B and Fe. The content of micronutrients in maize straw also depended on the year of cultivation and the relationships looked similar. Concentrations of B, Cu, Zn, Mn and Fe in maize straw were differentiated more by the applied fertilization. Significantly the highest amounts of B, Cu, Zn, Mn and Fe were removed with the maize aerial mass in 2016, when the meteorological conditions favoured the growth of this plant. The unit uptake of micronutrients for the production of 1 t of grain was also more considerably affected by the weather conditions than by the applied fertilization. The contribution of grain to the accumulation of micronutrients varied significantly between the years, and ranged for particular elements as follows: B - from 35 to 44%, Cu - from 28 to 34%, Zn - from 42 to 52%, Mn - from 7 to 13% and Fe - from 15 to 17%.

The paper demonstrates the influence of different mineral fertilization with phosphorus and potassium on the concentration of copper (Cu) and manganese (Mn) in the ear leaf of maize at the stage of flowering (BBCH 65) as well as the contents and accumulation of the nutrients studied in maize when fully ripe (BBCH 89). A single factor experiment was carried out in 5-year-cycle (2007-2011), in the randomized complete block design. The experiment was conducted as a part of a long-term stationary trial. The investigation comprised 8 different P and K treatments: the absolute control, exclusive of one of the main nutrients (P - WPN or K - WKN), reduced amount of phosphorus and potassium (to 25% - W25 and to 50% WP50, WK50) as well as recommended amounts of basic nutrients (NPKMg - W100 and NP*KMg, P* - P* as PAPR - W100 PAPR). Evaluation of the nutriational status, performed in the ear leaf of maize at flowering stage, showed that regardless of fertilization treatment applied, the concentration of copper was lower than normative values, whereas that of manganese ranged within the optimal scope. At the same time, there was found a significant relationship between the grain yield obtained and acquisition of both copper and manganese by maize at flowering stage (stronger for manganese, r = 0.614). The total accumulation of copper and manganese in fully ripe maize was significantly differentiated as a result of mineral fertilization. The total uptake of Cu and Mn was reduced under the conditions of 10-year lack of P fertilization. Uptake reduction was considerably more advanced when K fertilization was absent for 10 years. Regardless of the experimental factor effects, more than 50% of the total copper uptake was accumulated in grain, whereas the majority of manganese was accumulated in maize leaves (50-64% of the total uptake). Correlation analysis showed a significant relationship between maize grain yield and the total accumulation of copper, whereas that of manganese was observed only in 3 of 8 treatments tested (WPN, WP50 and W100 as PAPR).

Copper is required for many enzymatic activities in plants and for chlorophyll and seed production. Most Minnesota soils supply adequate amounts of copper for crop production. However, copper deficiency can occur in high organic matter and sandy soils. The amount of copper available to plants varies widely among soils. Copper in the soil is held with clay minerals as a cation and in association with organic matter. Copper deficiencies often occur in soils with peaty soils and high concentrations of organic matter. Sandy-textured soils are more likely to be copper deficient than loams and clays. Soils that contain greater amounts of oxides and carbonates tend to have low available copper. Soils with a pH of 7.5 or greater should be monitored when crops sensitive to copper are grown. In corn, copper deficiency first appears on new leaves as they come out of the whorl and develop a bluish green tint. New leaves may emerge from the whorl as spiraled. Necrosis may occur on older leaf-tips and edges and may die. Corn response to copper has not been documented in Minnesota. Corn is only moderately sensitive to copper deficiency. Copper deficiency is rare in soybeans. Soybean response to copper has not been verified in Minnesota. Use soil and plant tissue tests on organic soils to determine deficiencies and need for fertilizer. Copper can be broadcast or incorporated before planting and can also be applied as a mixture with other fertilizers. Copper is not recommended for mineral soils in Minnesota, due to lack of research. Copper sulfate is the preferred source of copper fertilizer because of low cost compared to chelated sources. Copper use efficiency is improved if the fertilizer is water soluble and the particle size of the fertilizer is small. A single application of copper can last for many years. There is a narrow range between copper deficiency and toxicity. Copper toxicity can persist for an extended period of time and is difficult to correct because of copper-s low solubility in water. Toxic concentration of copper in soil affects seed germination, root system development and plant vigor.

Background and aims: Rhizosheath, the soil attached to plant roots, may enhance drought resilience by improving water and nutrient uptake. This study evaluates the effects of rhizosheath formation on water and nutrient absorption from soils with different textures and moistures. Methods: Two maize inbred lines R109B (Rh +) and Ky228 (Rh-), known for their distinct rhizosheath formation yet having identical root morphology, were cultivated in loamy sand and loamy soils. When plants were 45 days old, a controlled soil drying cycle was initiated and parameters such as plant transpiration rate (E), leaf water potential ( Ψleaf ), and soil water content/potential were monitored. At the end of soil drying cycle, the total nutrient uptake in the plants' shoots was assessed. Results: Rh + demonstrated a denser rhizosheath, particularly in loamy sand, correlating with increased root hair development. Rh + plants in loamy sand had a 1.73-fold increase in normalized mass rhizosheath compared to loam soil. In moderate moisture, Rh + exhibited improved soil-plant-water relationships, evidenced by higher midday E and Ψleaf in loamy soil than Rh-. However, no significant differences were noted under severe drought between Rh + and Rh-, likely attributed to diminished root hairs functionality. In loamy sand, Rh + plants exhibited 1.5 times higher phosphorus uptake, 1.46 times higher calcium uptake, and 2.02 times higher manganese uptake compared to Rh-. Conclusion: Root hair development is a crucial factor in rhizosheath formation. The efficacy of the rhizosheath in enhancing water and nutrient uptake is significantly influenced by soil texture and moisture conditions.

Methods: Two Iowa State on-farm trials (2012-2014) in central Iowa evaluated B, Cu, Mn, and Zn in corn-soybean rotations on fields with no recent manure or micronutrient history (Webster silty clay loam and Clarion loam). A soil-application trial (six treatments: control; B, Mn, or Zn banded; a banded mixture; a broadcast-incorporated mixture, 4 reps) used NuBor 10 (0.5 lb B/acre banded, 2 lb/acre broadcast), Broadman20 (5 lb Mn/acre), and EZ20 (5 lb Zn/acre). A separate foliar trial (control; B, Cu, Mn, or Zn alone; a four-nutrient mixture) sprayed Max-In Boron/Copper and MicroBolt Zinc/Manganese twice per season (V5/V6 and V8/V10 for corn, R2/R3 for soybean), totaling 0.16 lb B, 0.08 lb Cu, 0.33 lb Mn, and 0.495 lb Zn/acre. Soil B was tested by hot-water method; Cu, Mn, Zn by DTPA and Mehlich-3. Grain was sampled and analyzed for micronutrient concentration. Findings: No statistically significant corn or soybean grain yield increase occurred from any micronutrient applied to soil or foliage in any trial-year (soybean 34.7-58.0 bu/acre; corn 162-234 bu/acre range across trials), though fertilization often raised grain micronutrient concentration. Soil Zn (DTPA) ranged 0.9-6.0 ppm; Iowa's only regional interpretation (deficient below 0.9 ppm for corn) correctly predicted the lack of response. Lack of response to Cu and Mn also matched other states' interpretations, since soil levels exceeded their sufficiency thresholds. For B, only the lowest end of other states' sufficiency range (0.5-2 ppm) could apply to Iowa; using the higher end would have incorrectly predicted a response in some site-years. Conclusion: regional soil-Zn interpretations for corn remain reliable, but B, Cu, and Mn interpretations from outside Iowa should be applied cautiously.

Methods: Two Iowa State on-farm trials (2012-2014) at the Armstrong/Neely-Kinyon farms in southwest Iowa evaluated B, Cu, Mn, and Zn on a Marshall silt loam with no recent manure or micronutrient use. A soil-application trial (control; B, Mn, or Zn banded; a banded mixture; a broadcast-incorporated mixture; 4 reps) used NuBor 10 (0.5 lb B/acre banded, 2 lb/acre broadcast), Broadman20 (5 lb Mn/acre), and EZ20 (5 lb Zn/acre). A foliar trial (control; B, Cu, Mn, or Zn alone; a four-nutrient mixture) sprayed Max-In B/Cu and MicroBolt Zn/Mn twice per season (V5/V6, plus V8/V10 for corn or R2/R3 for soybean), totaling 0.16 lb B, 0.08 lb Cu, 0.33 lb Mn, and 0.495 lb Zn/acre. Soil B was tested by hot-water method; Cu, Mn, Zn by DTPA and Mehlich-3. Crop sequence was soybean(2012)-corn(2013)-soybean(2014). Findings: No statistically significant corn or soybean yield increase occurred from B, Cu, Mn, or Zn applied to soil or foliage in any trial-year, despite yields ranging normal to very high (soybean 38-67 bu/acre; corn 198-220 bu/acre); fertilization often increased grain micronutrient concentration without a yield benefit. Soil Zn (DTPA) for non-fertilized plots ranged 0.5-1.7 ppm (marginal to adequate by Iowa's corn-only interpretation of <0.9 ppm deficient), consistent with the lack of response. Lack of Cu and Mn response agreed with other states' higher sufficiency thresholds, since observed soil levels exceeded them. For B, other states' interpretations predicted a yield increase in some years/trials that was not observed. Conclusion: Iowa's Zn interpretation for corn remains reliable in this soil, but B, Cu, and Mn recommendations imported from other states did not reliably predict yield response at this southwest Iowa site.

Methods: On-farm trial at Iowa State's Muscatine Island farm on a Toolesboro sandy loam (pH 6.2, 3.6% organic matter), with corn in 2012 and 2014 and soybean in 2013, no prior manure or micronutrient history. Six treatments (control; B, Mn, or Zn banded; a banded mixture; a broadcast-incorporated mixture) were replicated four times on the same plots each year. Rates: boron (NuBor 10) 0.5 lb B/acre banded or 2 lb/acre broadcast; manganese (Broadman20) 5 lb Mn/acre; zinc (EZ20) 5 lb Zn/acre, both banded and broadcast. Non-limiting P, K, and S were applied uniformly. Soil B was tested by hot-water extraction, Mn and Zn by DTPA and Mehlich-3. Corn ear leaves were sampled at silking (R1) and whole plants at V5-V6; soybean trifoliates were sampled at V5-V6 and R2-R3. Findings: No statistically significant corn or soybean grain yield response occurred from B, Mn, or Zn in any year (corn 185-234 bu/acre; soybean 54-58 bu/acre). Fertilization increased corn tissue B and Zn concentrations at V5-V6 but rarely at R1, and rarely raised soybean tissue concentrations at either stage, attributed to dilution from growth. Initial soil Zn (DTPA) ranged 1.2-2.3 ppm, above Iowa State's 0.9 ppm deficiency threshold for corn (the only regional soil-test interpretation available), correctly predicting no Zn response. Applying other states' higher B, Mn, or Zn soil/tissue sufficiency thresholds to this site would have incorrectly predicted yield increases for several nutrient-crop combinations. The authors concluded there was no economic yield benefit to B, Mn, or Zn application on this sandy soil, reinforcing that Iowa-specific Zn interpretations were reliable while imported out-of-state thresholds were not.

This study investigated the effects of micronutrient fertilization on corn and soybean grain yields through two field experiments conducted from 2012 to 2014 in Iowa on Marcus silty clay loam. The trials evaluated both soil applications (boron, manganese, and zinc) and foliar applications (boron, copper, manganese, zinc, and a multi-nutrient mixture). Baseline soil tests indicated that initial levels of copper, manganese, and zinc were generally adequate or high relative to regional sufficiency thresholds, while soil boron levels fell into intermediate ranges. Although fertilizer treatments frequently increased the concentration of micronutrients within the harvested grain, neither soil-applied nor foliar-applied micronutrients produced statistically significant grain yield increases for corn or soybean in any trial or year. The authors concluded that standard regional soil-test interpretations successfully predicted the lack of yield response for copper, manganese, and zinc. However, for boron, interpretations used in certain states incorrectly suggested a potential response even though none was observed. Overall, the findings indicate that micronutrient fertilization provides no economic grain yield benefit for corn and soybean when initial soil test levels are sufficient.

Studies are limited that focus on change in concentration and accumulation of secondary and micronutrients in corn (Zea mays L.) plant fractions and across corn hybrid development periods. This research was conducted in 2007 and 2008 to evaluate the partitioning of secondary and micronutrients across vegetative and reproductive stages at the plant-fraction level for 1960- and 2000-era hybrids. Two popular hybrids for each era were grown, with measurement of nutrient concentration and content in several plant and grain fractions. Secondary and micronutrient concentrations in plant fractions were lower in 2000- than 1960-era hybrids with most nutrients, except ear shoots and tassels for certain nutrients. However, nutrient content was consistently greater in 2000- compared to 1960-era hybrids in the whole plant and fractions at most development stages, except tassels and ear shoots. In tassels, nutrient content was mostly smaller in 2000-era hybrids, but in ear shoots content was similar. The accumulation rates of most nutrients per growing degree day (GDD) were greater in the reproductive period for 2000-era hybrids, but similar among eras in the vegetative period. Remobilized nutrients from vegetative to reproductive components were similar between era hybrids, except Ca and Fe, and positive except Fe, Mn, and B. It is apparent that greater nutrient content in newer hybrids was driven mainly by associated nutrient uptake rates and greater dry matter (DM). Despite the greater nutrient content with the modern hybrids, removal with grain or stover harvest would still be small for S and micronutrients.

This Ohio State Extension bulletin (AGF-519) synthesizes 194 micronutrient fertilizer trials in Ohio corn, soybean, and alfalfa (1976-2017) to guide practical management. Per Tri-State Fertilizer Recommendations, Ohio soils generally supply adequate micronutrients, but deficiencies of B, Cu, Mn, and Zn can occur under specific conditions: Cu on acidic peat/muck (pH<5.3) or black sand for corn/wheat/oats; Mn on peat/muck (pH>5.8) or lakebed soils (pH>6.2) for soybean/corn; Zn on peat, muck, or mineral soil (pH>6.5) for corn and soybean. Recommended tissue sufficiency ranges (ppm) for corn (ear leaf at silking) are Mn 20-150, Fe 21-250, B 4-25, Cu 6-20, Zn 20-70; for soybean (upper trifoliate before flowering) Mn 21-100, Fe 51-350, B 21-55, Cu 10-30, Zn 21-50, Mo 1.0-5.0. Across 33 corn trials, micronutrient fertilization raised yield by under 1%; across 144 soybean trials it raised yield about 1%, with Mn the only micronutrient showing consistent (though infrequent) response ? significant in 6 of 109 soybean Mn trials and 3 of 23 Mn-blend trials. B had no effect in 8 of 9 corn trials. Three recent studies (2013-2016) found soybean responsive to foliar Mn in only 1 of 32 paired trials (sandy, dry soil), and no yield response from B/Cu/Fe/Mn/Zn blends applied broadcast or foliar to corn or soybean at three sites, with tissue levels within sufficiency ranges. Recommendation: because soil tests poorly predict micronutrient availability and yield responses are rare, growers should combine visual deficiency scouting, soil testing, plant tissue analysis, yield-map monitoring, and awareness of high-risk soil/crop combinations (Table 1) before fertilizing. Always leave an unfertilized check strip and use yield monitors or weigh wagons to verify an economic response before adopting micronutrient fertilization broadly.