Micronutrients

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~ 18 elements have been
identified as essential for
the growth of all plants
Soil
C OH
air & water
N K Ca Mg P S
Cl Fe Mn Zn B Cu Mo
macronutrients
micronutrients
0.1%
V
Ni
Needed by
Si some plants
Na
Co
N = 100
http://web.missouri.edu/~umcsnrsoilwww/webpub05/micro1_2005rev.htm
Some elements (e.g. Se, I, As, Cr)
have been identified as essential for
animals but not for plants.
Boron is the only element that has been
identified as essential for plants
but not for animals
Inorganic nutrient forms taken up by plants
Co2+
Micronutrients have very important roles in plant metabolism
Classic concept of yield
response to nutrient availability
……
Crop yield
Micronutrients
Macronutrients
tend to have a
tend
to have
narrow
asufficiency
broad
range
sufficiency
range
Nutrient availability
Micronutrient deficiency
symptoms tend to show
up on new leaves
Nutrients used in
abundance tend to be
easily moved around
Negative
interactions
6.5
7.5
Suggested soil test levels for selected micronutrients in IL
SOIL TEST LEVEL (LB/ACRE)
MICRONUTRIENT AND PROCEDURE
VERY LOW
LOW
ADEQUATE
0.5
1.0
2.0
Iron (DTPA)
--
<4
>4
Manganese (DTPA)
--
<2
>2
Manganese (H3PO4)
--
<10
>10
Zinc (0.1N HCl)
--
<7
>7
Zinc (DTPA)
--
<1
>1
Boron (alfalfa only) hot water soluble
Unfortunately
soil tests for micronutrients
have limited value
•
sampling and soil test methods are less reliable
• calibration databases are inadequate
Plant tissue levels of micronutrients
often provide a better indication of
micronutrient needs than soil test
results
Critical tissue nutrient levels for corn, soybeans and alfalfa
Lower nutrient levels in designated plant tissue
indicates that nutrient deficiency is likely.
http://iah.aces.uiuc.edu/pdf/Agronomy_HB/11chapter.pdf
Micronutrients deficiencies are normally
associated with one or more of the following
five situations:
(1) highly weathered soils
(2) coarse-textured soils
(3) high-pH soils
(4) Organic/muck soils
(5) soils that are low in organic matter because
erosion or land-shaping processes have
removed the topsoil.
If one or of these situations applies and soil test
levels and/or plant tissue levels are low, evaluation
of micronutrient fertilizers is recommended.
Boron (B) deficiency is a common occurrence on alfalfa in IL.
Characteristic symptoms of the deficiency are yellowing of the upper leaves,
eventually turning to a purpling color, along with stunting of the upper stems.
Deficiency symptoms for B are similar to leaf hopper damage. Deficiency
symptoms are most commonly observed during drought conditions. If B
deficiency has previously been observed, it will likely occur whenever alfalfa is
grown in that field unless B is applied on an annual basis.
Boron fertilization in IL
On sandy soils, apply 1 lb of boron per acre after the first cutting
of alfalfa each year. On heavier soils, 3-4 lb/acre after the first
cutting (yr 1) is normally adequate for the life of the stand.
Boron should not be applied to the alfalfa seedbed as it can
damage germinating seeds and should not be applied to alfalfa
the year proceeding corn.
Low soil test levels of B are a good indicator that alfalfa will
respond to fertilization with B, but field scouting for deficiency
symptoms may be just as informative.
Correlation between soil test levels of B and corn or soybean
response to B is low. According to the U of I, there are no
confirmed B deficiencies on either corn or soybean in Illinois.
Foliar
of Boron
NCDA application
recommendations
for Boron:
Adequate
boron
nutrition
is
all
brassicas:
2 lbs
per acre
Crops
with
high
demand
for
boron
may
critical for high quality
benefit
from foliar
applications
of
cantaloupes
& cukes:
1 lb per acre
vegetable
crops
boron (~ 0.2 lbs B/acre) at the following
peppers
andto
tomatoes:
1 lb
percrops,
acre
times: prior
heading of
cole
prior
in root crops, and at
okra: to
0.5root
lbs swell
per acre
first bloom for tomatoes and okra.
Manganese deficiency (stunted plants with green veins in yellow or
whitish leaves) is common on high pH (alkaline) sandy soils,
especially during cool, wet weather in late May and June.
Suggested treatment is to spray either manganese sulfate or a
manganese chelate complex onto the leaves soon after the
symptoms first appear. Broadcast soil applications of Mn are often
ineffective because the Mn becomes unavailable.
Foliar application of MnEDTA at rates as low
as 0.15 pound Mn per acre in mid-June to
beans planted in early May has resulted in
significant yield increases in IL.
Delaying application until early July has
sometimes provided a slightly higher yield
response than mid-June applications. Multiple
applications may be necessary to optimize
yield.
Are Roundup Ready™ Soybeans more likely
to experience Mn deficiency ?
There is a growing body of evidence that RR soybeans
are more likely to experience Mn deficiency than non-RR
soybeans.
Researchers at Purdue University have attributed this to
less effective Mn utilization within RR beans and
interference with Mn uptake.
Impact of glyphosate on Mn transforming microorganisms
Impact of glyphosate on fusarium colonization of soybean roots
Far reaching effects of glyphosate on soil chemistry and ecology
Impact of low levels of glyphosate
on metal micronutrient concentrations in
“non target” plants
*
A recent study at the U of I found that
the amount of "flash" following
glyphosate application increased with
glyphosate rate, but that foliar
application of Mn had no impact on the
amount of "flash", leaf Mn content, or
crop yield.
It is likely that glyphosate effects on
yield related to Mn immobilization only
occur when Mn levels are approaching
deficiency.
Summary of recent research
Caution should be taken when mixing Mn
and other micronutrients with glyphosate.
Dry flowable products show the most antagonism,
while chelates show the least. Antagonism may
result in reduced weed control.
It has also been reported that glyphosate inhibits
the uptake of Mn applied to plant foliage prior to,
with, and for up to eight days after glyphosate
application.
Soybeans normally outgrow the stunted, yellow appearance
of Fe chlorosis. As a result, it has been difficult to measure
yield losses or decide whether or how to treat affected
areas.
Research in Minnesota has shown that timing of Fe
application is critical to attaining a response. Researchers
recommend that 0.15 lb/acre of iron as iron chelate be
applied to foliage within 3 to 7 days after chlorosis
symptoms develop (usually in the second-trifoliate stage of
growth). Waiting for soybeans to grow to the fourth- or fifthtrifoliate stage before applying iron resulted in no yield
increase.
Chloride
According to the U of I, chloride (Cl) deficiency has
not and is likely to be observed in IL. The Cl
requirement is much less than that of K, and each
time that K is applied as 0-0-60, there is as much Cl
applied as K. Chloride deficiency of wheat has been
observed in states where potassium deficiency is
rare (and thus 0-0-60) is not normally applied.
There is no reliable soil test for Cl in Illinois.
Copper
Copper (Cu) deficiency is rare in the U.S.
and has not been observed in Illinois.
Sweet corn and wheat are two of the crops
most sensitive to Cu deficiency.
Limited reports of the deficiency have been
reported in Michigan and Wisconsin on high
organic matter soils (mucks and peats).
Molybdenum
Molybdenum (Mo) differs from most of the other
micronutrients in that it increases in availability with an
increase in pH.
The deficiency is limited almost exclusively to legumes,
including soybeans grown on very acidic soils (pH< 5.0).
In nearly all cases, it is more economical to apply limestone
to correct the problem than to apply Mo. However, if you
must grow soybeans on very acidic soils, be sure to use a
seed treatment that includes molybdenum.
Soil pH is the only soil test that detects the potential for Mo
deficiency.
Zinc
Zinc (Zn) deficiency, while not common in IL, is much
more likely to occur on corn than on soybean.
Documented response to Zn has been limited to low
organic matter soils and sandy soils in northwestern
Illinois.
High pH (greater than 7.3) and very high P levels
increase the likelihood of Zn deficiency. If high P
levels have resulted from manure applications, Zn
deficiency is unlikely.
Soil test levels of Zn are poor indicators of yield
response to the application of Zn.
Zinc deficiency in corn is exhibited on the upper leaves
as interveinal chlorosis. The veins, midrib and leaf
margin remain green. As the deficiency intensifies “feather
like” bands develop on either side of the midrib and the
leaves may turn almost white (hence the term “white bud”
was coined to describe Zn deficient corn plants); internodes
are short resulting in stunted plants.
http://www.cropsoil.uga.edu/~oplank/diagnostics70/Symptoms_/Corn/Images-Corn/images-corn.html
Summary
None of the micronutrient soil tests are very
reliable for predicting crop response to
fertilization.
If soil test levels are high, the likelihood of response to fertilization
is very low. If soil test levels are low to medium, the potential for
response to the applied element may be high, or it may be low.
Decisions about micronutrient fertilization should take into
account the sensitivity of the crop to be grown, soil characteristics
that affect the availability of the element, such as soil pH, organic
matter, soil texture, and soil P level, soil test levels and tissue test
levels.
If multiple factors indicate potential for deficiency,
fertilization on a trial basis is probably a good risk.
Metal-EDTA complex
Micronutrients can
be blended with
macronutrient
fertilizers
Segregation is
likely to occur if
granules are not
all the same size
Mn, B and Cl help crops to resist fungal pathogens
Chloride (Cl), usually in the form of potassium chloride (KCl), has been
shown to reduce the severity of some fungal diseases.
Adequate Mn nutrition reduces the incidence of foliar disease in most
crops. Mn is needed for the synthesis of lignin and phenols,
compounds used by plants to combat infection by pathogens.
Boron (B) deficiency has been linked to the production of small fissures
and cracks that may be the initial entrances for fungal pathogens.
Micronutrient Malnutrition
 Affects nearly half the world’s population
 More than 840 million people cannot meet
their basic daily food and nutritional needs
 About 2 billion people, mostly women and
children, are at risk from diseases, premature
death, and lower quality of life linked to
deficiencies of vitamin A, iodine, and iron
Global Prevalence of Iron, Vitamin A
and Iodine Deficiencies
Source: USAID
HarvestPlus:
NOT a silver bullet,
but an additional weapon to fight deficiency
Supplementation
Commercial
Fortification
Biofortification
Dietary
Diversity
Biofortification
• Useful genetic variation exists in key crops
• Breeding programs can enhance nutritional
quality traits, which for some crops are highly
heritable and simple to screen for
• Desired traits should be stable across a wide
range of growing environments
• Nutritional quality traits should be combined with
superior agronomic characteristics (e.g., higher
yields)
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