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Thread: Mn for Soybeans-

  1. #1
    Senior Member jabber1 is on a distinguished road
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    Mn for Soybeans-

    Couldn't find the old thread that addressed this so here's a new one.

    This from little ol' p = Pioneer

    Manganese Fertilization of Soybean
    Manganese (not to be confused with the macronutrient
    magnesium) is one of the 16 elements essential to plant growth
    and production. Since this element is needed in relatively small
    amounts compared to others such as nitrogen and potassium,
    manganese is considered a micronutrient.
    Manganese has several very important roles in the plant,
    including its function as an activator or cofactor of at least 35
    enzymes. Manganese is part of the structure of an important
    antioxidant (superoxide di****ase) that protects plant cells
    by deactivating free radicals, which can destroy plant tissue.
    Manganese plays vital roles in photosynthesis as a structural
    component of the photosystem II water-splitting protein. It also
    serves as electron storage and delivery to the chlorophyll reaction
    Manganese is suffi cient in most soils to supply crop needs,
    but may be defi cient in dry conditions, sandy soils, high organic
    matter soils (especially peat and muck), and soils with high pH.
    When defi cient, manganese can be supplied by fertilizer in several
    forms, by foliar and soil-applied methods.
    Of all micronutrients, manganese tends to be the most
    common defi ciency noted in soybean production. Manganese
    defi ciencies, however, tend to respond positively to remedial
    treatments of manganese (when they are timely). As with all
    nutrients, yield responses are only attainable when manganese
    is defi cient and therefore limiting yield. This article describes
    manganese requirements, defi ciency symptoms, soil and plant
    sampling, and fertilization practices in soybean production.
    Chemical Properties and Availability of Manganese
    in the Soil
    Manganese exists in a number of forms in the soil, including
    soil solution Mn2+, exchangeable Mn2+, organic compounds,
    various minerals, and as other ions. However, the only form
    known to be plant available is the manganese ion Mn2+ in soil
    solution. Manganese availability to plants largely depends on
    soil texture, organic matter, pH, and weather conditions.
    Soil pH – Manganese is most soluble and therefore available
    to the plant at a pH of 5 to 7. In alkaline soils (pH above 7),
    manganese may form insoluble compounds, making it unavailable
    to the plant. For every increase of 1 pH unit, manganese
    availability decreases 100-fold. In very acidic soils, however,
    manganese can reach toxic levels. Liming soils to appropriate
    pH can help avoid this situation.
    Soil Organic Matter – Organic matter and manganese ions
    will combine to form insoluble compounds that are not accessible
    by plant roots. This is exacerbated by high soil pH.
    Soil Aeration and Moisture – Available manganese is affected
    by soil aeration and moisture. Waterlogged and anaerobic
    (or “reducing”) environments are conducive to more Mn2+
    in solution. In contrast, very dry soils tend to have less Mn2+ in
    soil solution. Additionally, low moisture conditions will slow the
    growth and activity of soil microbes that also cycle manganese
    in the soil.
    Weather Conditions – Hot and dry conditions result in less
    manganese in available form as they typically cause dry soils.
    Other Nutrients – High levels of copper, zinc, and iron can
    reduce uptake of manganese. Conversely, acid-producing fertilizers
    including ammonium sulfate, MAP, and DAP can increase
    manganese availability. Potassium chloride (0-0-60 potash) may
    also increase plant uptake of manganese.
    Manganese Defi ciency Symptoms in Soybean
    Visual defi ciency symptoms include interveinal chlorosis
    (yellowing between the veins) on the younger leaves, followed
    by necrosis (brown/black spots of dead tissue) and yield loss if
    the defi ciency progresses.
    Figure 1. Manganese defi cient soybeans. Uppermost (youngest) leaves
    show interveinal chlorosis while the veins remain green.
    (Photo courtesy of Ron Gehl, NC State University)
    Areas of defi ciencies will likely vary across the fi eld, and
    since the availability of manganese is tied to soil factors, knowing
    the fi eld’s history over time can be helpful in diagnosis.
    Fields or fi eld areas with a history of manganese defi ciencies
    will be more likely to show defi ciencies in future soybean crops.
    Figure 2. Manganese defi ciency on a muck soil near Lansing, MI.
    (Photo courtesy of Ron Gehl, NC State University)
    Soil and Plant Analysis for Manganese
    Because yellowing of plants can be due to a number of
    factors (iron, potassium, or magnesium defi ciency, herbicide or
    insect injury, soybean cyst nematode damage, poor nodulation,
    etc.), good scouting practices and tissue sampling are often
    needed to confi rm a specifi c nutrient defi ciency. Plant tissue
    analysis is the usual method to confi rm a suspected manganese
    defi ciency, as soil testing tends to be much less predictive.
    Plant Sampling – The standard plant sampling technique
    for soybeans is to take the newest trifoliate leaves that are fully
    opened (keeping in mind that manganese is not very mobile and
    new leaves will show defi ciencies). Randomly sample plants
    to get a representative sample of the affected area, though
    consider a separate sample of non-affected plants to make
    a comparison. When sampling leaves, remove the petiole (or
    stem-like structure that holds the leaf to the soybean stem) so
    just leaf tissue is represented in the sample. Be sure to follow
    your diagnostic laboratory’s specifi c sampling and shipping

  2. #2
    Senior Member jabber1 is on a distinguished road
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    Plant Tissue Test Interpretation/Fertilizer Recommendations
    – Typically, plant tissue contains from 20-500 parts per million
    (ppm) of manganese. A level of 21 or fewer ppm is generally
    considered defi cient, though some recent research shows that
    defi ciencies (and response to fertilizer) are some-times noted
    at 30-40 ppm. Also, some varieties of soybeans seem to be more
    sensitive to manganese defi ciencies than others. Since relatively
    small quantities are necessary for treatment, foliar applications
    could be used. Some fi elds with a known history of
    defi ciencies (e.g., muck soils) may require multiple applications
    and soil amendments of manganese.
    Manganese Fertilizers and Application
    Choosing a Source of Manganese – Generally, “blanket”
    application of any nutrient without confi rmation of a defi ciency
    is not recommended. Applications of manganese to soybeans
    with suffi cient manganese can result in toxic concentrations
    and yield loss. Once a defi ciency is identifi ed and confi rmed,
    a fertilizer source and method can then be determined. There
    are a few different fertilizer sources of manganese effective
    for correcting defi ciencies (Table 1). These sources can be
    grouped as:
    • Inorganic products as salts and oxides - manganese sulfate,
    manganese chloride, and manganese oxide
    • Organic chelates - Mn-EDTA, Mn-glucoheptonate, Mn-citric
    acid, and others
    • Organic non-chelates (natural organic complexes)
    Method of Application – Soil broadcast applications of
    manganese tend not to be very effective compared to foliar
    treatments. This is because soil can render the treatment unavailable
    in a short period and soil application may not be timely
    enough for remediating a defi ciency in-season.
    Foliar applications are the preferred method of supplying
    manganese to a growing soybean crop. Usually 0.2 to 0.5
    pounds of manganese per acre is suffi cient per application. If a
    grower is not tankmixing manganese with glyphosate, the manganese
    sulfate form will work as well as the chelated forms for
    foliar feeding, so cost per pound can be the deciding factor in
    product choice.
    Special Considerations when Tankmixing Manganese
    with Glyphosate – Some growers may decide to include a manganese
    product with glyphosate for post-emergent weed control
    in glyphosate-tolerant soybeans, saving application costs
    for two products. Research studies have shown that mixing
    glyphosate with micronutrients and other herbicides can cause
    antagonism, that is, loss of effectiveness in controlling weeds
    Table 1. Common manganese fertilizer sources.
    Manganese Fertilizer Comments
    Manganese sulfate
    (MnSO4 • 4H20)
    ~ 26-28% Mn
    Suitable for soil or foliar application,
    though foliar is preferable to soil
    application. May chelate glyphosate
    in tankmix solution and lessen weed
    control effi cacy.
    Manganese chloride
    (MnCl2) 17% Mn
    Manganese oxide
    41 – 68% Mn
    Low solubility. Must be fi nely
    ground to be effective in the soil.
    Not recommended for foliar use.
    Synthetic manganese
    chelates (Mn-EDTA
    and others)
    5 to 14% Mn
    Preferred foliar fertilizer source because
    of lower rates and decreased
    interactions with tankmix partners
    such as glyphosate (EDTA seems
    to be the least detrimental). Not
    recommended for soil application.
    Organic residues and
    0.01 to 0.05% Mn
    Manure and other organic residues
    contain a number of micronutrients,
    including manganese.
    and reduced absorption of the nutrient. This is a result of “hard”
    water interacting with the glyphosate molecules. “Hard” water
    typically describes water containing a high level of metals, including
    the familiar calcium, magnesium, and iron found in well
    water, but also metal nutrients that might be added for fertilizer
    purposes (like manganese). Glyphosate will interact with
    (or chelate) these metals, and reduce the effectiveness of weed
    control and nutrient absorption. In order to avoid this interaction,
    a grower can either:
    1) Spray the products separately (glyphosate application
    followed by manganese 7 to 10 days later), or
    2) Use spray-grade ammonium sulfate (AMS) in the carrier
    for tankmixing with a chelated form of manganese (EDTA
    Ammonium sulfate is used to “soften” the carrier water before
    glyphosate and manganese are added to the tank. Refer to
    the glyphosate label for the appropriate amount of AMS (usually
    8.5 to 17 pounds per 100 gallons of carrier). Manganese EDTA
    is the form of manganese that is least antagonistic when tankmixed
    with glyphosate.
    When mixing products for application, the mixing order is
    important to assure that the carrier is “conditioned” before the
    potentially-chelating products are added to the tank. Add products
    to the tank in this order:
    Step 1. Add water Step 2. Add AMS
    Step 3. Add glyphosate Step 4. Add manganese EDTA.
    As with any product, read and follow label directions.
    ate S
    t d d
    nese EDTA
    ®, SM, TM Trademarks and service marks of Pioneer Hi-Bred. ©2010 PHII

  3. #3
    The foliar I have been using is an 18-3-3 low salt formulation. The nitrogen is slow release. Mn and Boron are included in this mix.
    Let me add a step or two to their mix.

    1) add water to 2/3 of tank
    2) Add 1-2 lb citric acid per 100 gal
    3) Add AMS
    4) Add lots of antifoam
    5) gly
    6) Mn/Liquid fertilizer/Corn Syrup
    7) top off water

    In a perfect world, we would be applying the Mn seperately.

    You can subtract out the AMS if you run the foliar also.

  4. #4
    Senior Member 48 is on a distinguished road
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    RCR: I don't use AMS. I use a liquid replacement like Choice. I condition ALL the water with the pump running=agitation. Smoke a cig. Then add glyphosate. I use Fighter-F for anti-foam.

  5. #5
    Senior Member 48 is on a distinguished road
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    jabber: Good post. But, it is pretty common knowledge that glyphosate ties up Mn...in the tank...in the plant...and in the root zone. There was a PhD at Purdue doing some excellent work on this, but he retired. Big M prolly forced it. lol.

  6. #6
    Senior Member ECI is on a distinguished road ECI's Avatar
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    Boy this has been a ***** to post up the damn thing was to long so this will be page one ,Just hope I can find the other half ! Ken

    Dr. Don Huber's presentation
    Written by Jim Martindale
    With full credits to Dr. Huber and Jerry Carlson


    Jerry Carlson's Notes from Dr. Don Huber presentation Dec. 16, 2009

    High yield hybrids: More N must be taken up after tasseling. Also,
    high yield corn can use ammonium better, as opposed to nitrate
    nitrogen. 75% ammonium, 25% nitrate N.

    NServe takes nitrous ammonius out of the rhizosphere. Other
    organisms fill the void about 9 days.

    Glyphosate takes entire groups of organisms out of the soil.
    Biological buffering becomes very difficult when you have a compound
    that persists in the soil for years.

    About 80% of our nitrogen losses are conversion to nitrous oxide, and
    volatilization. Not leaching, which occurs only in sandy soils.

    A lot of our ag chemicals are chelators. Tordon chelates copper.
    Glyphosate is a powerful chelator for many ions.

    There’s ten tons of living material in an acre of soil. It’s a
    living entity and the quality of its life impacts mineralization of

    Manganese availability depends on biological activity; it can only
    use Mn2+ and not Mn4+ Most bio availability occurs between 5.2 and
    7.8 pH.
    Take-all in wheat is a manganese converter. Amplify the take-all
    fungus with carbon and energy, it amplifies its growth.

    Filaments of Take-all coat themselves with Manganese Oxide, MN04.
    Take-all ties up manganese and can impact the following crop.

    Improved nutrition reduces disease. Manure on wheat stimulates
    resistant to rhizoctonia.
    Copper deficiency: Ergot on wheat, produces LSD.

    Ergot sclerotia -- closes the capillaries.

    Closest I’ve seen in my 55 years to a prolonged recovery period from
    the impact of glyphosate.

    Inserting the RR gene in plant reduces Mn uptake efficiency. It adds
    a stress on the plant’s physiology. Another system is running in the
    plant. If you have a good mineral soil with lots of buffering, the
    loss of efficiency may not hurt yield much. But in a MN-deficient
    soil, yield could suffer and really bomb out. This is why many of
    the soybean varieties are off the market.

    In soils that 15 years ago we were concerned about manganese
    toxicity, we’re not seeding manganese deficiency because we’ve
    changed the soil microflora so much with glyphosate applications.

    Iron, manganese available to plants only in reduced form (H).

    Sulfur only available in oxidized form.

    Gypsum gives you a good source of soluble CA plus soluble Sulfur.

    Converting nitrate nitrogen into amine form, amino acids, can take
    16% of the energy (sugars) built by the plant. This is why high-
    yielding corn needs a 75% ammonium form of N, and 25% nitrate form.

    Fusarium wilt in melons and fruit -- go for Nitrate form and calcium.

    nitrapyrin = N-Serv

  7. #7
    Senior Member ECI is on a distinguished road ECI's Avatar
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    And know the R E S T of the story .

    Recognizing nutrient disease interactions with Glyphosate

    Canadian: I’ve seen all those symptoms, just never associated them
    with glyphosate.
    Going to glyph, we changed tillage and crop sequence too.

    Learn to watch for the symptoms; there’s a limited way the plant can
    express itself.

    Single most important indicator of head blight is use of glyphosate
    in the past three years.

    Glyphosate was patented as a metal chelator. Monsanto patented as a
    herbicide. Needs ammonium sulfate in the tank to tie up metals and
    minerals. Binds minerals -- Ca, Cu, Fe, Mg, Mn, Zn.

    EDTA is a chelator of 13.

    Glyphosate penetrates readily, moves throughout the plant, chelates
    with minerals and it’s not available for the plant from then on.

    Micronutrients tied up won’t be available for any future growth.
    About a fourth of the glyphosate is exuded from the root system.

    Once the initial flashing is over,

    There is 1,000 times more glyphosate in the vascular system than
    there is unbound minerals. There’s an abundant supply of glyphosate
    to chelate all minerals in the plant for about two weeks.

    There’s an 80% reduction in Mn uptake.

    Translocation of Fe, MN, Zn from root to shoot is reduced by more
    than 80%. Once it’s chelated it doesn’t move.

    Chelating means bonding. EDTA turns loose of minerals eventually,
    glyphosate does not.

    Liberty Link has degradation within a two-day period.

    All of the degredation products of glyphosate are toxic to the plant,
    even the RR resistant plant.

    100% of the kill of plants with glyphosate is to open a secondary
    pathway for microbial organisms.

    Chelation of micronutrients -- accentuates drought stress. Three-
    fourths of the gly moves to shoot, repproductive and roots.

    About a fourth of the gly moves into the soil via living roots.

    We don’t know of any organism that uses gly as a nutrient source.

    It sits there and accumulates for several years. It’s toxic to N-
    fixing microbes, Mycorrhizae, Earthworms, PGR organisms, Mycorrhizae,
    Bacterial shikimate pathway.

    We are starting to see glyphosate in grain, such as wheat planted
    after glyphosate crops.

    In Humans, we need a lot of micronutrients too.

    Mandated phosmet insecticides chelated copper in cattle in England,
    and there was an outbreak of BSE.

    There may be some organism found to break it down, but haven’t heard
    about it.

    Glyphosate is an amino acid; it looked like it would biodegrade.
    However, the French forced Monsanto to take “biodegradable” off the
    label because they couldn’t demonstrate it.

    USDA shows mineral content of conventional and GMO grain is lower
    than organic.

    Bob Kremer, University of Missouri, analyzes gly in the soil. Lab in
    Pennsylvania tests for metabolic degredation products.

    The compound hangs around a long time, both in the plant and in the

    In the soil, desorbed by phosphorus.

    Directly toxic to N-fixers
    PGPR organisms.
    When you put glyphosate out, you kill them.
    All organisms with shikimate pathway are inhibited.

    Richard Dick at Ohio State -- stimulation of fungus can immobilize up
    to 150 lbs. of potassium.

    If the politics win with the 15-year glyphosate review, we’ll see a
    continuing degradation of our productive base. This is already
    evident in the Pacific Northwest, where it’s hard to get a decent crop.

    China has moved into RR cotton, they’re struggling.

    We’ll have to import more food unless we reverse course on GMO/

    When you’re in the hole and keep digging, it doesn’t do much good.

    We should use it a lot more judiciously.

    RR sugarbeets have very little resistance to rotting in the pile.
    They last two weeks. But being judicious would help; you don’t need
    a gallon of glyphosate on sugarbeets.

    Glyphosate tolerant weeds are finding other pathways, not just the
    manganese which is an enzyme inhibitor.

    We have aphid invasions because the amino acid is more appealing to
    aphids, stimulating the aphid population.

    Alfalfa -- 20-ft. taproot. Could be translocating glyphosate into
    the water table.

    We’ve had a 1500-fold increase in herbicide use, primarily because of
    glyphosate’s advertising as environmentally friendly.

    We’ve ignored the challenge. Now we’re approaching the consequences.
    I have a tremendous confidence in using the abilities to use the
    knowledge the Lord has given us.

    Bottom line is that glyphosate stimulates fusarium, nutrient
    oxidizers, and soilborne pathogens.

    Texas -- corn fails after glyphosate cotton . Shikimate test out
    the top. Lots of 100% failures. Across the road, Non-gmo corn doing
    great. How many insurance claims will the federal insurance program
    allow on this basis?

    Have 50 years of failure on biological control of crop diseases on
    regular soils.

    My only successes were in building desert soils with biological

    Davies spent his whole career into trying to reduce pathogens in
    soils with biological organisms.

    Within six hours, you have colonization with pythium. In just six hours.

    Whole groups of organisms disappear in a glyphosate environment.

    Glyphosate reduces lignin content of soybeans. Also reduces amino
    acid content of soybeans.

    Reduces water efficiency. Takes twice as much water to produce a
    pound of dry matter.

    Phil Jones, 8200 paired trials, presence of RR gene imposes a yield
    drag. There’s another genetic system for the plant to support. So
    we have two negative impacts: soil impact plus gene impact.

    How would I get rid of it? Will the RR gene transfer to unintended
    crops and weeds? That was the basis for the alfalfa injunction... in
    five years, all alfalfa would be RR. Brazil is looking for ways to
    help farmers pull back from RR genetics in corn and beans.

    Desorption of glyphosate with phosphate: Re-releases the compounds
    in glyphosate and has a greater chelation effect.

    Sudden Death Syndrome in soybeans is definitely related to the rise
    of fusarium in RR soybeans.

    Barney Gordon, Kansas. Gene present reduced yield effectivness. Took
    additional manganese to offset the presence of the gene.

    Jeff Neal, journalist in England... had written story about myth of
    increasing yield.

    Tissue tests may show adequate Mn, Zn, but doesn’t reveal if it’s
    chelated with glyposate in the plant and therefore ineffective for
    plant health.

    Mineral reduction in RR crops:

    RR treated beans 45% lower in Mn, 26% lower in Ca.

    Dan Skow, veterinarian with International Ag Labs in Fairmont, MN,
    says they’re adding more manganese to dairy rations because of the
    deficiency in soy protein.

    Vet: Brazilian corn tests in 2005 were much lower in fusarium molds;
    if Brazil has lower mold counts than the U.S. over time, where should
    the Japanese buy?

    Soil organisms kill the weed, not the glyphosate itself. That’s what
    happens when you shut down the shikimate pathway. In effect,
    glyphosate is our 24th worst disease.


    Diseases increased by Glyphosate.

    Many of those which were controlled in the past are coming back.

    And many of the wilts and other fungi are losing host specificity,
    and are impacting more crop species as well as becoming more virilent.

    Wait 8 days before spraying manganese to remediate the lack of
    manganese. What’s happening is that glyphosate is being released
    and ties up applied manganese.

    Manganese carbonate as a treatment to remediate manganese tied up.

    When you have an iron defificency in the soil, you have a manganese

    (My side note: In high iron soils of the southeast, maybe there’s
    abundant Mn and little yield drag. .. perhaps that’s involved in high
    yield response to SoySoap in the Southeast while we see muted
    response here)

    Tree trunk is a highly absorptive area for glyphosate

  8. #8
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    Here's another good one from ISU also a two parter ! After reading this I thing I have a good idea what Kip is up to , LOL Hope I can get the other part . Ken

    Iowa State University Weed Science 1 [url]www.weeds.iastate.edu/mgmt/2010/glymn.pdf[/url]
    University Extension Department of Agronomy
    Glyphosate-Manganese Interactions in Roundup Ready Soybean
    Shortly after the introduction of Roundup Ready (RR) soybean questions arose whether these varieties and/or glyphosate applications to them alter manganese (Mn) relations compared to conventional soybean varieties. It is well documented that certain cations, including Mn, can reduce the performance of glyphosate when the cations are present in water used as a carrier. The complexes formed between glyphosate and metal cations are not absorbed as efficiently as free glyphosate alone, resulting in reduced weed control. The primary role of AMS used with glyphosate applications is to minimize formation of the cation-glyphosate complexes. This article will review research that has investigated the interactions between RR soybean and Mn relations, rather than what happens in the spray tank. Although the focus of this article is Mn, glyphosate would interact similarly with other cations (e.g. calcium, iron, magnesium).
    Mn efficiency of soybeans with Roundup Ready trait
    Some of the first reports of Mn-related problems with RR soybean were reported by researchers at Purdue University in 2001 (Dodds et al. 2001). They found that growth of a RR variety grown on a Mn-limiting soil was inhibited more severely by Mn deficiency than a conventional variety. On a non-limiting soil there was little difference in growth of the two varieties. The research was repeated in 2002 using additional varieties, and some, but not all, RR varieties were found to be more sensitive to Mn-deficieny than conventional varieties (Dodds et al. 2002). Gordon (2007), at Kansas State University, reported that under a high-yield environment a RR variety was responsive to Mn fertilization whereas a conventional variety was not. Based on this research, it could be concluded that RR varieties are less efficient at Mn absorption/utilization than conventional varieties. However, due to the limited varieties evaluated in the studies, it is just as likely that the difference in response to Mn between the RR and conventional varieties was due to some other difference among the varieties rather than the RR trait. The 2002 Purdue study included several RR varieties and found that not all RR varieties were responsive to Mn, suggesting that the Mn response is not directly linked to the RR trait. Research in California found no evidence that the RR trait affected Mn relations (Rosolem et al. 2009). Research in Brazil found 1 out of 3 RR varieties had lower Mn concentrations in new leaves than the non-RR parental line, but the other two varieties were not affected (Zobiole et al. 2010).
    Interactions of glyphosate and Mn within soybean
    A second issue with glyphosate and Mn is related to interactions between the two molecules in the plant, rather than the characteristics of RR varieties. An injury response often seen following glyphosate application to RR soybean is chlorosis in newly emerged leaves. The symptoms are similar to those attributable to Mn deficiency, so it has been implied that glyphosate may interfere with Mn relations within the plant. Glyphosate is poorly metabolized by plants and accumulates in growing points, and can accumulate at concentrations capable of forming complexes with Mn or other metal cations. Zobiole et al. (2010) reported that glyphosate applications decreased Mn and other nutrient concentrations in RR varieties. They also reported significant reductions in shoot and root biomass due to the glyphosate applications, something that is normally not observed. However, the majority of research has not identified differences in Mn absorption, accumulation and availability between glyphosate-treated and non-treated RR soybean (Bott et al. 2008; Rosolem et al. 2009; Nelson 2009). Rosolem et al. (2009) stated that glyphosate injury symptoms in RR soybean have been misinterpreted as Mn deficiency. Ebelhar and Hart (2006) in Illinois were unable to prevent chlorosis associated with glyphosate by supplementing soybean with additional Mn, nor prevent yield loss associated with high

  9. #9
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    And know Page two !

    Iowa State University Weed Science 2 [url]www.weeds.iastate.edu/mgmt/2010/glymn.pdf[/url]
    glyphosate rates (2X-4X) with supplemental Mn. While the chlorosis that appears following glyphosate application mimics Mn deficiency, the symptom has been attributed to accumulation of AMPA in new leaves (Reddy et al. 2004). AMPA is a degradation product of glyphosate.
    Interactions of glyphosate with Mn in the soil
    It has been speculated that glyphosate may interact with Mn relations by reducing availability of Mn in the soil via chelation. It has also been suggested that glyphosate could reduce the availability of soluble Mn by affecting the activity of microorganisms that control the oxidation-reduction status of soil. Glyphosate may enter the soil profile either by direct contact during spraying or through exudation from roots of treated plants. Glyphosate released into the soil has been shown to affect growth of microorganisms in the vicinity of the roots and in the zone of application (Kremer et al. 2005), but there are no published data documenting reduced soil availability of Mn or other nutrients. While it is possible that glyphosate could temporarily tie up essential elements, it would not specifically target Mn, or any other micronutrient, but rather would interact with the most prevalent cations in the vicinity of the roots. In Iowa soils, the majority of glyphosate would likely interact with the highly abundant Ca and Mg rather than Mn, and also organic matter. Furthermore, levels of Mn in Iowa soils probably are sufficient because there have been no reports of Mn crop deficiency symptoms in Iowa. Crop Mn deficiency symptoms occur in some regions, and this is where interactions between glyphosate and Mn nutrition have been reported.
    So the question is whether RR soybean varieties require different Mn management practices than conventional varieties and if this is really a problem under Iowa conditions. Glyphosate is known to form complexes with Mn and other metal cations that may reduce both the availability of the cation and glyphosate activity. However, most interactions between RR soybean and Mn have been observed in areas with soils known to be deficient in Mn. Although there has been research indicating RR soybean may respond differently to Mn than conventional varieties, the majority of research does not support this observation. The best recommendation remains to manage RR soybean similar to conventional varieties in terms of fertility management.
    Prepared by: Bob Hartzler
    February 24, 2010
    References Cited
    Bott, S., T. Tesfamariam, H. Candan, I. Cakmak, V. Römheld, and G. Neumann. 2008. Glyphosate-induced impairment of plant growth and micronutrient status in glyphosate-resistant soybean (Glycine max L.). Plant Soil 312:185-194.
    Dodds, D.M., Huber, D.M. and M.V. Hickman. 2002. Micronutrient levels in normal and glyphosate-resistant soybean varieties. Proc. North Central Weed Sci. Soc. 57:107.
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    Zobiole, L.H.S., R.S. de Oliveira Jr., D.M. Huber, J. Constantin, C. de Castro, F.A. de Oliveira, and A. D. Oliveira Jr. 2010. Plant Soil 328:57-69.
    Acknowledgements: This article was reviewed by Mike Owen, John Sawyer and Antonio Mallarino.

  10. #10
    Senior Member glowplug is on a distinguished road
    Join Date
    Dec 2008
    Wow, ECI you've been a busy guy. That took over one cup of coffee to read.

    I'm still on the fence. Huber makes a lot of claims. But I'm not seeing the plant health issues provided my clients are up to current on lime and soil nutrients.


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