1. Gary L. Dick DBA GLD Consulting
2600 Denver Ave.
Longmont, CO 80503 (Mail)
(and)
990 Kearney County Line Road
Holcomb, KS 67851 (No mail)
303.995.1312 cell 303.776.6850 hmkinross17@earthlink.net
Originally to Clientele January 11, 2012: File title Revised February 02, 2016
Dear Clients;
About this same time last year I attempted to give you a summary of what I know about Molybdenum (Mo) and
what it means to our alfalfa cropping potential. In conducting further literature search, I have learned a few
new things but still find that specific answers and guidelines are hard to come by. To date I have only found a
loose consensus as follows:
1. At some levels Mo can be considered “deficient” in soils. That level escapes the general literature.
2. If we suspect Mo deficiency, we need to consider adding “some” and in “some form”.
3. Foliar applications of Mo may be the best means of rectifying a potential deficiency,
4. Excess Mo can be toxic to ruminants in rare situations, and there are interactions of Mo with Cu and
sulfate (SO4).
5. The best way to monitor Mo levels is foliar sampling.
6. Mo appears to be better-researched as a toxic heavy metal in municipal and industrial effluent than
as an essential crop nutrient.
7. Should Mo applications become necessary, it is fairly economical to rectify the situation with very
small amounts of Mo added to other foliar nutrients.
I will recap and edit what I wrote last year with my new (although not consensus) findings. If you don’t want to
wade through the following discussion, as I advised last year, skip to “Gary’s Bottom Line on Molybdenum
on Alfalfa” at the end of this document. I find all this information fascinating.
General Discussion
In the process of revisiting the literature, I found we may have an additional, seemingly chronic, issue with
Copper (Cu) deficiency, especially in relation to small grain production. I also found intermittent commentary
(no data) that Mo may be limiting in our area for Corn, Soybeans, and, surprisingly, Cotton. The reasons I
keep pursuing the Mo issues are as follows:
a) Added information: Starting in about 1996 and continuing to the most recent soil samples pulled
on Dec. 18, 2012 from the transition from Arkansas river flood plain into the northern sand hills, I
believe I have repeatedly documented Mo deficiencies. In some cases, foliar results correlated with
perceived soil deficiencies.
b) Molybdenum is essential for nitrogen-fixing bacteria in legume nodules to provide adequate nitrogen
for plant growth. It is as important as adding nitrogen fertilizer to non-legumes.
c) Added information: Molybdenum is essential for other crops that are heavy Nitrogen (N) users. It
functions in nitrogen metabolism apart from being incorporated into nitrogen fixing nodules. Matt
Hagny, independent consultant from Wichita, states in Farm Journal that sunflowers, soybeans,
peas, and canola are most sensitive to low Mo. He states that alfalfa, wheat, corn, and sorghum can
also be affected by low Mo. My question: Could our perceived Mo deficiencies in soils be affecting
N metabolism in corn and small grains? Could our low Mo levels be reason why Cotton and Canola
have not yet been successful in our immediate area?
d) Because Mo can be toxic to ruminant animals under certain conditions and there is a Mo/Cu
interaction in ruminants it is imperative that we don’t overdo Mo applications.

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e) Until I find a concensus of “learned opinions” that better define the Mo parameters, I have decided I
will create my own guidelines and trust that they translate into benefits for you as you attempt to
optimize your alfalfa quantity and quality.
Recap and Additional Information
1. Added information: There are conditions under which alfalfa plants cannot meet their nitrogen
needs from nodule activity or uptake of residual nitrates. These conditions would be a) cold soils
below 45F because overall metabolism declines dramatically, b) excessively hot soils above 85F
because nodule bacteria activity declines or ceases, c) and dry soils because everything shuts
down and plants have reduced solar collection ability and hence reduced energy for metabolism.
Mike Ottman, University of CA, says it takes substantial yield potential to split the N-N bonds in
atmospheric nitrogen and produce useable nitrates. I would think that having low Mo to start with
would almost amount to devastating consequences for alfalfa plants under the stress levels we
have seen the last two seasons. According to Ottman (I used to work with him at Univ. of AZ – he
is a very thorough and believable researcher) alfalfa only gets ½ of its nitrogen from nodule
activity, so if the nodules can’t function, there you have it.
2. Molybdenum is essential for adequate production of nitrogen for legumes. Adequate nitrogen
leads to better stem extension, larger leaves, better protein production, and better tonnage and
quality (if balanced with other essential nutrients.) Mo is critical to function of nitrogen-fixing
bacteria in legume nodules and it apparently functions in iron (Fe) absorption and translocation in
at least some plants. Molybdenum plays a role in a multi-step chemical process in both legumes
and non-legumes that converts nitrates to a form used to build proteins and nucleic acids.
3. Changed information: As far as Mo toxicity issues go, as long as we do not a) apply large
amounts of Mo, b) harvest before rain or irrigation, or c) fail to monitor Mo through foliar testing, we
do not need to be concerned.
4. Mo is unique among micronutrients in that it becomes more available as soil pH increases. Most
micros become more available as pH decreases. I think the take-home inference here is that if our
soils have high pH (alkaline/saline) and soil tests still show low Mo, then we probably have a real
Mo-deficiency situation.
5. Added Information: Darrel Smith, Farm Journal Magazine, summarized research conducted by
Matt Hagny, an independent consultant from the Wichita area. Matt discovered Mo deficiencies in
his local soils when researching pale green areas in soybean and wheat fields. Mo applications to
fields deemed Mo-deficient turned fields green again and increased soybean yields 5.7 bu./A. This
was accomplished by applying 0.02 to 0.04 lbs./A actual Mo to foliage. Matt concluded that
applying Mo to soil was totally ineffective at alleviating deficiencies due the the type of clays in his
part of KS.
6. Added Information: Crops such as soybeans and alfalfa can produce Mo-deficient seeds when
grown in Mo-deficient soils. Then, if such seeds are planted into Mo-deficient soils, they will show
Mo deficiency. Large-seeded crops such as soybeans, if grown in Mo-sufficient soils, may not
show Mo-deficiency even if planted in Mo-deficient soils. I feel this implies that whether or not
alfalfa was grown in Mo-sufficient or deficient soils, seed treatments containing Mo can only
support alfalfa for a short time – maybe only part of the first season.
7. Added Information: Apparently legume nodules can concentrate what little Mo a plant acquires
from the soil in a deficiency situation. However, keep in mind that Mo is needed elsewhere in the
plant as a critical part of its ability metabolize nitrogen.
8. Apparently Mo forms complexes in plants (one being phosphomolybdate) and this allows plants to
absorb large amounts of Mo without toxic effects (to the plant). I’m guessing that the reverse of

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this (decomplexing in the rumen??) may also explain why ruminant animals can extract toxic levels
of Mo.
9. Added information: For a number of fields sampled in Fall, 2011, I requested that Olsen’s
Laboratory run two large groups of samples all on the same day using that day’s equipment
calibration. I had hoped this would reduce variability. The uniformity of results was positive in that
it showed we are consistent in how we take samples and the values that seem exceptionally low
are documentable and repeatable.
10. Added and consolidated information: Rather than try to describe all the pertinent Mo levels in
narrative form I have summarized results in Table 1.
Table 1. Comparative Mo Values and Comments
Mo Levels Where Comments
1.50 to 2.00 ppm Soils -- Worldwide “Average Worldwide” range.
0.50 to 5.00 ppm Soils -- Worldwide Proposed “Normal” soil levels for
purposes of establishing base-
lines for environmental pollution.
0.04 to 0.12 ppm Soils Thought by some to be the low
critical values for plant growth.
0.50 to 1.50 ppm Soils Thought by others to be the low
critical values for plant growth
0.10 ppm Soils The value for a “Mo-deficient” soil
used in a 2008 project which
cited references from the 1950s.
0.05 to 0.50 ppm Soils Listed as marginally adequate to
deficient in one CA study.
0.40 lb per acre Soil-applied in fertilizer Increased alfalfa yields
significantly in one CA study.
2.00 to 3.00 ppm Soils Gary’s GLD Consulting soil
values for reasonable alfalfa
production.
0.08 to 34.0 ppm Soils – Local -- 1996 through
2011 results Lakin, Deerfield,
and Ulysses area.
Range observed. Based on late-
2011 results, I think soil values
over 10 ppm may be contami-
nation of samples with Mo-
containing agricultural steels or
similar.
Below 0.01 ppm detectable
limits
Soils – Wichita area – Matt
Gagny
Wow! Note: The labs could
detect detectable amounts.
“Too low for most laboratories
to detect”
Soils. Oregon State “Soil
Test Interpretation Guide”
1996
Find a different lab!! – Oh, come
on. All the labs I have used can
detect Mo just fine.
0.3 to 10 ppm Foliar, forages. Operating range: Below =
deficient, Above = toxic to
livestock
1.00 to 1.50 ppm Foliar, forages “Sufficient” range used by
Olsen’s Laboratory
0.48 to 5.00 ppm Foliar, forage Range found in recent foliar
testing.
3.00 ppm Foliar Gary’s GLD Consulting
target range for optimum
alfalfa production.

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12. Added/Revised Information: High levels of sulfates in the soil or added levels of sulfates in
fertilizer or irrigation water have been documented to interfere with Mo uptake from soils. There is
some thoughts that inadequate levels of phosphorus (P) reduces Mo uptake from soils but that
high levels of P in acid soils can also inhibit Mo utilization. This is thought to be due to the similar
size of the sulfate, Mo, and phosphate molecules and how they are actively transported into plant
roots. We have some fields with what I feel are almost excessive levels of S and we
commonly apply moderate levels of S, so I would infer that high S levels and relatively high
pHs in some of our area fields may be accentuating Mo deficiencies. Complicating factors:
Addition of nitrate-N, magnesium (Mg), and phosphates when pH is around neutral all enhance Mo
uptake. However, addition of copper, manganese (Mn), and sulfates inhibit Mo uptake from soils.
This is important in some settings: see the next point below.
13. Note to those who apply feedlot or Tyson effluent – those effluents are low in nitrates,
phosphates, and Mg, but very high in ammonium and somewhat high in sulfates. This, in
my opinion, could cause or accentuate Mo deficiencies, especially on Mo-deficient soils.
14. There are no research studies that define how laboratory soil extractions correlate with plant
uptake. With many nutrients we can say “if the soil contains X nutrient, we can apply Y amount for
optimum growth. Not so with Mo at this stage of knowledge.
15. It appears that ammonium molybdate is the preferred form of Mo for foliar feeding. This seems
strange (see point 12 above) in light of ammonium inhibiting soil uptake of Mo. Maybe the
ammonium vaporizes off and leaves the molybdate molecule behind and free for easy uptake.
Unfortunate reality here: As of spring, 2011, when Tom Broz at Kugler inquired of suppliers,
ammonium molybdate was not available in the quantities needed for a reasonable price.
That leaves sodium molybdate as our Mo source at the moment.
16. Mo application can enhance iron (Fe) uptake and translocation and Mg can enhance Mo uptake.
Now, consider this: What happens if we have low Mo in a low-Fe, low-Mg soil? Too many
questions, not enough answers.
17. Animal manure, municipal wastes, and Tyson effluent are generally very low in Mo. Recent
manure samples analyzed by Olsen’s Laboratory confirm this.
So, what does it all mean? Here is my bottom line based on accumulated knowledge:
Gary’s Bottom Line on Molybdenum on Alfalfa
-- Do not arbitrarily apply Mo. Apply only if a need is documented based on present knowledge.
-- Unless I learn otherwise, I will use a target soil level of 2 ppm as a trigger point for taking tissue samples for
Mo. To date, this trigger point seems reasonable for our situation.
-- If tissue samples confirm low soil-Mo we need to get some Mo applied as foliar feed.
-- It appears that application of 0.02 to 0.04 lbs./A actual Mo metal is sufficient to temporarily rectify
documented deficiencies. Since it is not likely that toxicity will be an issue at those application levels, and it is
unreasonable to assume we will have a custom blend for each field, if our standard foliar feed blend for alfalfa
contains those low levels of Mo we should not encounter any problems.
-- Frequency of followup Mo applications should be based loosely on need documented by foliar testing.
Fields that start out at soil test levels of 2.5 ppm Mo or less should be target first. On soils testing low in Mo, it

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would be wise to test for Mo if transitioning to one of the non-legume crops known to be responsive to Mo.
Before planting alfalfa or soybeans on soils previously untested for Mo, soils should always be tested for Mo.
-- Apply Mo with a topdress nutrient blend specific for other needs that may be identified in tissue testing. It
seems prudent to consider using a nitrate source rather than an ammonium source as nutrient and Mo carrier.
It would appear that including a magnesium chelate and iron chelate may be beneficial. However, if Mg is
needed, it is difficult to combine with other fertilizers. If need for Cu or Mn, or S is documented it would seem
prudent to apply those separately (alternate nutrients on subsequent foliar feed events. Avoid sulfates and
ammonium in carrier fertilizer. If sulfur is required, a separate chemigated application of 12-0-0-26 may be
better.
--In the event we find pH levels creeping down (not likely), rectifying the pH should be addressed before
applying Mo
-- Continue to pursue availability of ammonium molybdate as the material of choice for foliar feed.
-- Regarding cost, just figure that a little bit of Mo may be worth a big amount of nitrogen made available to
plants – and that means extra protein, more efficient plant metabolism, and likely more tonnage and better feed
value.
-- If we apply Mo foliarly, we need to allow at least one irrigation or one substantial rain between application
and cutting to avoid possibility that forage could contain levels of Mo toxic to cattle.
What About Copper? Very Important for Wheat and Barley, Maybe Alfalfa
Since I mentioned above that I discovered that some of our soils may be low in copper (Cu), I will summarize
briefly what I found. Since 1989 various Cu studies have been conducted in Alberta, Canada. They drew
some new conclusions and feel they have a good level of confidence in what they found about Cu deficiencies
and corrective action. Prior to the mid 1980s agronomists in the region thought Cu deficiency was confined to
some rare, organic soils and that local mineral soils were inherently high enough in natural Cu that deficiencies
were rare. Depending on soils, they estimated over 3 million acres were Cu-deficient.
Prior to 1985-88, the sole test of Cu-sufficiency or deficiency was a 0.2 ppm soil test level. They found that the
0.2 ppm cutoff made a dfference for wheat and barley. Research in Saskatchewan had indicated that 0.4 ppm
should be the cutoff level for Cu in soils. Alberta researchers conducted additional research in their area and
determined that 0.6 to 0.8 ppm was a more appropriate cutoff level. As of 1999 they go so far as to list soil test
levels of 0.60 to 1.00 ppm as borderline deficient in some cases. At this point, the cutoff levels become
important for us in Southwest Kansas because we frequently find Cu levels in the 0.6 to 1.0 ppm range.
Alberta and Saskatchewan researchers noted it was those farmers striving for optimal fertilizer and yield
management that were most often affected by the low Cu levels. The first indication of Cu deficiency was
decreased yield and lower than expected test weights. Interestingly, weed control also suffered. They also
found that although the test weights were unexpectedly low, protein levels were markedly high because there
was nothing in the kernels to give added bulk and weight and “dilute” the protein.
Those Canadian researchers have developed a comprehensive table for considering relevant agronomic
factors that come into play in diagnosing Cu deficiencies. They feel that Wheat, Barley, Alfalfa, and Corn may
benefit from closer scrutiny relative to Cu levels. We need to pay attention to this as we push the limits and
quality of our crops and as we use wheat and corn as rotational crops to get back to alfalfa.
References
Kevin Grooms and Bob Olsen, Olsen’s Agricultural Labaratory, conversations and emails. Approx. 1996-2012.
Tom Broz, Kugler Fertilizer Company, conversations and emails. Approx. 1996-2012.

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John L. Havlin, James D. Beaton, Samuel L. Tisdale, and Werner L. Nelson. Soil Fertility and Fertilizers: An
Introduction to Nutrient Management, 7th
Ed. Pearson/Prentice Hall, New Jersey. (lookup date)
Dave Mengel, KSU Soils Specialist. From email to Kevin Grooms. (date unknown)
A Little-Known Nutrient, A Farm Journal excerpt authored by Darrell Smith based on research work conducted
by Matt Hagny, independent consultant in the Wichita, KS area. Forwarded to me by Kevin Grooms, Olsen’s
Laboratory. 2006 Copyright.
R. L. Mahler. University of Idaho, CIS 1087. May, 2000. Molybdenum in Idaho.
M.K. Sandabe and U. Bapetel, 2008. The response of tomato (Lycopersicum esculentum) to the supplication
of molybdenum in a semi-arid soil of north eastern Nigeria. Int. J. Agri. Biol., 10: 97-100.
E. Solberg, I. Evans, D. Penny. September 1999. Copper Deficiency: Diagnosis and Correction. Alberta
Agriculture, Edmonton, Agronomy Unit, Plant Industry Division.
E. S. Marx, J. Hart, and R. G. Stevens. 1996. Soil Test Interpretation Guide. Oregon State University.
R. S. Lavado, C. A. Porcelli, R. Alvarez. 1999. Molybdenum in the Geosphere: Molybdenum in soil and
rocks. Science of the Total Environment, 1999, 232-3, pp. 185-191.
R. D. Meyer, R. L. Phillips, and D. B. Marcum. 1999. Molybdenum, Copper, and Selenium in Alfalfa and Other
Forages. Presented at 29th
California Alfalfa Symposium, Radisson Hotel, Fresno, CA.
Olsen’s Agricultural Laboratories interpretive guidelines. (lookup exact reference)