Quick facts
- Manganese (Mn) is one of eight essential micronutrients for plants.
- It is required for photosynthesis, nitrogen metabolism, lignin synthesis, root growth, and activation of many enzymatic systems.
- Deficiency of Mn in crops can lead to significant yield loss if not corrected properly.
- Most Minnesota soils supply an adequate amount of Mn for crop production.
Manganese in soils
The Earth's crust contains about 0.11% Mn. The availability of Mn varies greatly depending on soil types and other soil properties.
Specific soil conditions that affect Mn availability
- Soil pH: Manganese deficiency is likely to occur on heavily weathered sandy soils and peat or organic soils with a pH above 6.0. On mineral soils such as calcareous soil, Mn deficiency may occur with pH values of 6.5 or above. As soil pH decreases, plant available Mn increases. Manganese can be toxic in highly acidic (pH < 5.0) soil.
- Soil organic matter: Mn in the soil solution often becomes unavailable because ionic forms of Mn easily bind with organic matter.
- Moisture and temperature: Lack of soil moisture reduces Mn availability. Cold and wet soil may cause Mn deficiency in plants due to the combined effects of reduced mineralization of soil organic matter, reduced root growth, and reduced metabolic activity in roots affecting Mn uptake.
- Presence of other metal micronutrients in soil: Greater concentration of copper, iron, nickel, and zinc in the soil may induce Mn deficiency by reducing Mn uptake.
Crops that respond to manganese fertilization
Crops species and cultivars vary considerably in their response to fertilizer-Mn. Some crops are more sensitive than others. The table below lists some agronomic and horticultural crops grown in Minnesota that are sensitive to fertilizer-Mn.
Crop sensitivity to manganese fertilization
| High Sensitivity Crops | Medium Sensitivity Crops | Low Sensitivity Crops |
|---|---|---|
| Apples | Alfalfa | Asparagus |
| Cucumber | Barley | Blueberries |
| Dry edible bean | Broccoli | Rye |
| Grapes | Cabbage | |
| Lettuce | Carrot | |
| Soybean | Cauliflower | |
| Sugarbeet | Celery | |
| Wheat | Corn | |
| Onion | Potatoes | |
| Oats | Strawberries | |
| Peas | Sweet corn | |
| Potato | Tomatoes | |
| Radish | ||
| Raspberries | ||
| Snap bean | ||
| Spinach |
Manganese deficiency symptoms
Manganese deficiency symptoms vary by crops. Manganese is highly immobile in the plants. Deficiency symptoms first appear in younger plant tissues. A common Mn deficiency symptom for most crops is recognized by interveinal chlorosis (yellowing between the veins) in the young leaves while the veins remain dark green. These symptoms can often be confused with iron (Fe) deficiency. In dicots, green veins with Mn deficiency are often wider than with Fe deficiency and have a fishbone appearance.
Soybean
Young soybean leaves become chlorotic between the veins while the veins remain green. In severe Mn deficiency conditions, brown and dead areas appear on the leaves.
Following a glyphosate application, symptoms similar to Mn deficiency may appear. This symptom is known as glyphosate flash. In this situation, symptoms may only be temporary and new leaves will not likely be normal green in color.
Corn
Interveinal chlorosis appears in the young corn leaves while the veins remain green. Plants become stunted with short thin stems. In severe deficiency conditions, leaves turn yellow and white flecks appear in the interveinal chlorotic areas.
Small grains
In oats, gray oval-shaped spots appear at the edge of newly developed leaves when the plants are approximately at the 3 to 4-leaf stage. The symptom is known as “gray speck”. Multiple spots may appear. The spots generally get bigger as plants grow.
In wheat and barley, plants develop yellow parallel streaks on the younger leaves.
Onion
Interveinal chlorosis may occur on the outer leaves, wilted, and may develop tip burn. Plants become stunted and delayed bulbing may occur.
Potato and sugarbeet
In potatoes and sugarbeet, interveinal chlorosis begins in the younger leaves. Gray and black freckling may develop along the veins as plants grow. Potatoes show reduced leaf size.
Landscape plants
Some landscape plants such as maples and winterberry are susceptible to Mn deficiency when grown on calcareous soils. Symptoms include interveinal yellowing of the younger leaves and in severe cases leaf death.
Diagnosing manganese deficiency
Soil and plant tissue tests are recommended to determine Mn deficiency in plants.
Soil testing
The DTPA extraction method is suggested for measuring Mn concentration in soil. Some soil labs extract Mn using the Mehlich-III extraction solution. Data comparing the two tests has shown no correlation between Mn extracted with the DTPA test versus the Mehlich-III test and interpretations for either test should not be used for the other.
Currently, the DTPA test is not calibrated for agronomic crops in Minnesota soils. So soil test interpretations and fertilizer suggestions based on the DTPA Mn are not provided for grain and vegetable crops grown in Minnesota.
For vegetable crops grown on organic soils, Mn is recommended for sensitive crops if the soil pH is greater than 5.8.
Plant tissue testing
A deficiency of Mn can be diagnosed using plant tissue analysis. Plant tissue analysis should be used in conjunction with soil tests before arriving for a recommendation for using Mn fertilizer. Interpretations for various concentrations of Mn in plant tissue of several agronomic and horticultural crops grown in Minnesota are summarized in the next table.
Because tissue Mn concentration varies between growth stages and plant parts, tissue testing should be done on specific plant parts at specific times in the growing season for the interpretation of plant analysis to be accurate.
Sufficiency levels of manganese
| Crop | Plant part | Time | Sufficiency range |
|---|---|---|---|
| Alfalfa | Top 6 inches | Bud | 30-100 ppm |
| Apple | Mature leaves from new growth | Summer | 25-200 |
| Blueberry | Mature leaves from new growth | Summer | 25-150 |
| Broccoli | Mature leaves from new growth | Heading | 25-200 |
| Cabbage | Wrapper leaves | Head ¾ mature | 25-200 |
| Carrot | Oldest leaves | Mature plants | 50-200 |
| Cauliflower | Mature leaves from new growth | At heading | 25-250 |
| Edible beans | Most recently matured trifoliate leaves. | Bloom stage | 20-90 |
| Field corn | Leaves from base of ear | Initial Silk | 15-150 |
| Grape | Mature leaves | Nonfruiting – most recently matured leaf | 25-200 |
| Oat | 25 whole shoots | Head emerges from boot | 25-100 |
| Pea | Recently mature leaflet | First bloom | 30-400 |
| Potato | Most recently fully developed leaves and petiole | 40-50 days after emergence | 20-450 |
| Potato | Petiole | 40-50 days after emergence | 30 - 300 |
| Raspberry | Mature leaves from mid-section of primocanes | 2-3 weeks postharvest | 25-300 |
| Soybean | Most recently matured trifoliate leaves. | Early Flowering | 17-100 |
| Spring wheat | 25 Whole tops | As head emerges from boot | 25-100 |
| Strawberry | Most recently matured leaves | At flowering | 50-200 |
| Sweet corn | Unfurled leaves (5t leaf from tip) | 7-8 week-old plants, tassel start | 31-300 |
| Sugarbeet | 25 recently matured leaves | June-July, 50-80 days after planting | 26-360 |
Crop response to manganese fertilization in Minnesota
Soybean
Glyphosate-resistant soybean comprises 96% of the total acreage planted in Minnesota. Previous research in other U.S. states has documented that glyphosate-resistant soybean genotypes lowered Mn concentrations in trifoliate tissue compared to conventional soybean genotypes.
Studies conducted in Minnesota from 2011 to 2014 at 18 locations have shown tissue Mn concentrations were within the sufficiency range regardless of Mn fertilizer application. Application of fertilizer Mn did not significantly (P≤0.05) increase tissue Mn concentration at any location. There were no apparent issues with Mn toxicity even though some trifoliate Mn concentrations were above the range considered sufficient for soybean at the R1 growth stage.
Grain data collected from 12 sites during 2011 to 2014 showed no evidence of a yield increase due to the application of Mn.
Summary of main treatment (manganese source) effects on soybean trifoliate
| Year | Location | Mn soil test | OM soil test* | pH soil test | Trifoliate Mn conc -Mn** | Trifoliate Mn conc +Mn | Grain yield -Mn** | Grain yield +Mn |
|---|---|---|---|---|---|---|---|---|
| 2013 | Norman | 11 ppm | 3.70% | 8.1 | 112 ppm | 108 ppm | 26.8 bu/acre | 26.8 bu/acre |
| Redwood | 47 | 4.5 | 5.8 | 38 | 41 | 38 | 38.2 | |
| Olmsted | 35 | 2.1 | 5.8 | 76 | 76 | 40.1 | 40.7 | |
| Winona | 49 | 3 | 6.7 | 85 | 88 | 44.6 | 42.1 | |
| Sibley A | 27 | 7.3 | 7.4 | 113 | 123 | 36.4 | 36 | |
| Sibley B | 47 | 5.2 | 6.8 | 69 | 71 | 41.2 | 40 | |
| 2014 | Norman | 7 | 6.1 | 7.4 | 79 | 81 | 37.1 | 39 |
| Redwood | 57 | 4.4 | 5.4 | 68 | 66 | 61.3 | 61.3 | |
| Olmsted | 29 | 4.6 | 6.5 | 72 | 72 | 54.3 | 53.9 | |
| Olmsted | 33 | 2.2 | 5.9 | 80 | 78 | 38.3 | 37.9 | |
| Sibley A | 14 | 6.5 | 7.7 | 68 | 68 | 44.4 | 45.3 | |
| Sibley B | 32 | 4.8 | 7 | 50 | 51 | 52.1 | 51.8 |
Corn
No documented cases of Mn deficiency in corn have been reported in Minnesota. Yield data from eight trials conducted in Minnesota in 2011 are given in the following table. There was no significant yield increase at any location observed.
Summary of corn grain yield (15.5% moisture content) for plots with (+Mn) and without (-Mn) manganese fertilization.
| Site | Mn soil test | OM soil test* | pH soil test | Corn grain yield -Mn** | Corn grain yield +Mn |
|---|---|---|---|---|---|
| Oklee, 2011 | 4 ppm | 18.70% | 6.3 | 109 bu/acre | 109 bu/acre |
| Rochester, 2011 | 54 | 6.1 | 6.1 | 241 | 233 |
| Staples, 2011 | 24 | 7.1 | 7.1 | 197 | 199 |
| Westport, 2011 | 33 | 6.5 | 6.5 | 194 | 189 |
| Gaylord, 2012 | 6.3 | 6.4 | 185 | 199 | |
| Montgomery, 2012 | 3.1 | 7.4 | 195 | 195 | |
| Rochester, 2012 | 2.2 | 5.7 | 158 | 152 | |
| Rochester, 2013 | 2.1 | 5.8 | 177 | 178 |
Manganese toxicity
Manganese toxicity has not been reported in Minnesota. Manganese toxicity is likely to occur in acidic and poorly-drained soils that can be recognized by interveinal chlorosis with leaf-cupping and darkening of leaf veins of older leaves.
Necrosis may occur if toxicity is severe. In soybean, leaves become crinkled and cup down (Figure MN-4). Corn is tolerant to Mn toxicity. In potatoes, lower leaves died in severe Mn toxicity.
The following crops are susceptible to Mn toxicity: alfalfa, cabbage, cauliflower, dry edible beans, onions, potatoes, small grains and sugar beets. A high Mn concentration may induce Fe deficiency in plants.
Summary
Manganese is not recommended by the University of Minnesota for any crop grown in Minnesota, except for vegetable crops grown on organic soils.
Trials conducted with crops previously did not show any response to Mn fertilization. Mineral soils in Minnesota are likely to provide adequate amount of Mn for crops.
If there is any evidence of Mn deficiency, farmers and crop advisors are encouraged to confirm by conducting soil and tissue tests and report to the University of Minnesota nutrient management team.
Reviewed in 2023