1. 1
~ 9 micronutrients are essential
for all plants… identify 6!
Soil
C OH air & water
N K Ca Mg P S
macronutrients
??????????
micronutrients
0.1%
of plant dry matter
V
Many more elements are found in plants –
some of which can have beneficial (but not yet Needed by
proven essential) effects on plant growth some plants
Si Na
The following micronutrients are currently recognized as essential
for the growth of all plants: Cl Fe Mn Zn B Cu Mo Ni Co

2. 2
Which of the following crop response curves is most appropriate for a
macronutrient? How about a micronutrient? Explain your selections.
a) b)
micronutrients
macronutrients
Macronutrients have broad sufficiency ranges. In contrast,
micronutrients tend to have narrow sufficiency ranges and
care should be taken to avoid overapplication/toxicity.

3. 3
Identify 2 similarities and
2 differences between the
N and S cycles
Similarities with the N cycle Differences with the N cycle
• Many oxidation states • Very little S in the earth’s atmosphere
• Most of the S in soil is a component naturally (most of the S in the
of SOM atmosphere today is anthropogenic)
• Biological transformations are • Weathering of rocks is the primary
important e.g., mineralization and source of S
immobilization • Most global S in the earth’s crust
• Volatilization is a major loss pathway • Soil concentrations range from 10s to
1000s of ppm (as compared to 100s to
> 10,000 ppm N)

4. 4
Identify 2 reasons why S
deficiencies are increasingly
common in the Midwest
- Enforcement of clean air standards has reduced SOx
emissions from power plants and industry by > 50% in the
last 2 decades
- The S contents of current fertilizers are far lower than those
used historically.
- Higher crop yields are removing higher amounts of S from
soils as well as increasing the need for S.

5. 5
For any one of the materials identified below
calculate the appropriate rate to supply a crop with
10 lbs of S/ac. List material and rate.
Show work if you want the option of partial credit.
Ammonium sulfate (21-0-0) - 24%
Ammonium thiosulfate (12-0-0) – 26% S
Potassium sulfate (0-0-50) - 18% S
Sul-Po-Mag (0-0-22-S) - 23% S, 11% Mg
Gypsum aka calcium sulfate - 17% S
Elemental S – 90% S
lbs to supply
Material S content 10 lbs of S
AMS 0.24 41.7
ATS 0.26 38.5
Ksulfate 0.18 55.6
Sul-Po-Mag 0.23 43.5
Gypsum 0.17 58.8
Elemental S 0.90 11.1

6. Why is it a standard
practice for
orchardists to apply
foliar fertilizers
containing calcium?
Calcium deficiencies are common in orchard
crops and fruit quality is often improved by
foliar applications of Ca
6

7. 7
Micronutrients are primarily found within what general
category of molecules? Hint these molecules have special
shapes that enable them to activate chemical reactions.
I am an
enzyme

8. 8
Micro/secondary
nutrients Macronutrients
Limited movement within plants mobile within plants
Generally speaking what types of nutrient deficiencies show up on
upper leaves? What about lower leaves? Explain your answer.

9. 9
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.

10. 10
a) Which micronutrient appears
to be most affected by
glyphosate?
Mn
b) When is glyphosate application
most likely to result in yield loss?
Yield loss is most likely when crop uptake of
Mn would be borderline w/o glyphosate

11. 11
Mo
Does it matter if crop seeds are low in Mo?
Seeds that contain ample Mo can develop into high performing crops with little to no
additional Mo supplied by the soil. Crops grown from seeds that are low in Mo are much
more likely to experience Mo deficiency.
Some evidence suggests that crop seeds are
increasingly likely to be low in Mo

12. 12
In Illinois
Warning or caution statements are required on
the label for any product which contains 0.03%
or more of _a_ in a water-soluble form or
0.001% or more of _b_.
When 0.001% or more of ___b___ is added to an
agricultural fertilizer, the purchaser is to receive a
caution statement as follows: "CAUTION: This
fertilizer is to be used only on soils which respond
to ___b____. Crops high in ___b___ are toxic to
ruminants."
A = boron and b = molybdenum.

13. 13
The missing term = soil test(s)
_______ for micronutrients are NOT very reliable for
predicting crop response to fertilization.
If _______ levels are high, the likelihood of response to fertilization
is low. If ________ 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, _________ levels and tissue
test levels.
If multiple factors indicate potential for deficiency,
fertilization on a trial basis is probably a good strategy.

14. 14
Biofortification
(breeding for higher nutrient levels in crops)
NOT a silver bullet,
but an additional weapon to fight deficiency
Supplementation
Commercial
Fortification
Identify 2
other
strategies Biofortification
Dietary
Diversity

15. 15
Chloride
According to the U of I, chloride (Cl) deficiency has not
been observed and is unlikely to be observed in IL.
Why is chloride deficiency so unlikely in IL ?
Most IL farmers routinely apply “potash” aka muriate of potash (KCl)
Cl makes up ~ 48 % of the mass of “potash”
There is no reliable soil test for Cl in Illinois.

16. 16
What is meant by the term in the
center of this slide?
The acid infertility complex
The collective challenges faced by crops growing in acid soils

17. 17
Which micronutrient becomes more available as pH increases?
Mo = molybdenum
most
^
http://www.farmtested.com/research_pp.html

18. 18
What type of toxicity is common in soils with a
pH below 5.5?
Aluminum toxicity

19. 19
A coffee urn model is commonly used to represent
active and reserve acidity in soil. Do you think this
model is informative? Briefly explain.
Lime
Reserve acidity is requirement can
the primary supply not be accurately
of acidity in soil estimated based
active acidity
and can quickly
on just the
resupply the active
acidity (pH is a
Reserve current pH. Some
measure of active acidity measure of the
acidity). reserve acidity is
also needed.

20. 20
Soil acidity increases when H+ producing
processes exceed H+ consuming processes.

21. 21
Which plants received nitrate (NO3-)?
Which plants received ammonium (NH4+)?
A = nitrate
A B
B = ammonium
Uptake of
nitrate causes
plant roots to
Briefly release
alkalinity
explain your whereas
answer uptake of
ammonium
causes plant
roots to release
acidity.
Roots need to
maintain charge
balance
http://departments.agri.huji.ac.il/plantscience/topics_irrigation/uzifert/4thmeet.htm

22. 22
What happens to the acidity and alkalinity in
plant biomass when it is burned?
Oxides of
C, N and S
Acidity Alkalinity
Oxides of
Ca, Mg and K

23. 23
Identify 1 thing farmers can do to reduce the rate of
soil acidification other than adding lime.
Farmers can reduce the rate of acidification by using N fertilizers that
are less acidifying AND by using practices that reduce nitrate leaching

24. 24
The amount of lime needed to bring about a unit pH change depends
on the soil’s reserve acidity (which ↑with clay, OM and CEC)
The amount of lime needed to bring
about a 1 unit change in pH varies
widely between soils
WHY?

25. 25
“Illinois method” of determining lime requirement
8 tons/ac
Recommend a lime rate
for the following scenario
Soil belongs to the lime
group with highest
reserve acidity
Initial pH is 5.0
http://iah.aces.uiuc.edu/pdf/Agronomy_HB/11chapter.pdf

26. 26
Lime requirements determined using the
“Illinois method” assume the following:
A. A 9-inch tillage depth. If tillage is less than 9 inches, reduce the amount of
limestone; if more than 9 inches, increase the lime rate proportionately. In
no-till systems, use a 3-inch depth for calculations (one-third the amount
suggested for soil moldboard-plowed 9 inches deep).
B. Typical fineness of limestone. Ten percent of the particles are greater than
8-mesh; 30 percent pass an 8-mesh and are held on 30-mesh; 30 percent
pass a 30-mesh and are held on 60-mesh; and 30 percent pass a 60-mesh.
C. A calcium carbonate equivalent (total neutralizing power) of 90 percent.
The rate of application may be adjusted according to the deviation from 90.

27. 27
Goals of routine soil testing
rapid
cheap
predictive
broadly applicable
Identify 3 of the 4 goals we discussed in class

28. 28
What is a composite
sample ?
A composite
sample is a mixture
of multiple
(typically 5-10)
sub-samples
The U of Illinois currently
recommends collecting
1 composite sample per
2.5-acres.
120 acre field

29. 29
Soil management zones
Briefly describe and differentiate
between the management zone
and the grid sampling
approaches for soil sampling.
Soil 3
Grid sampling involves a uniform pattern
of high density sample collection Soil 4
(frequently 1 composite sample per 1-2.5 acres) Soil
1
In contrast, management zone
sampling involves collecting samples to
represent designated zones (of varying
size and shape) perceived to have
relatively uniform soil test levels.
Soil 2
What is needed to make the
management approach a
reasonable approach?
The management zone sampling approach
requires that you have enough understanding of soil variation to designate appropriate zones.

30. 30
Late summer and fall are often recommended
as the best times for collecting soil samples
Provide at least 2
reasons why.
- the soil samples used for soil test calibration are normally collected in
the late summer/fall
- potassium test results are most reliable during the late summer/fall
- nutrient uptake by summer crops has occurred
- soil is more likely to be dry

31. 31
Extractable nutrient levels are not directly
related to most of the factors controlling
nutrient uptake by crops during a growing
season.
Identify 4 factors that affect nutrient uptake
during a growing season.
Temperature, moisture, microbial activity, rooting
depth, root health, crop genetics…

32. 32
The man in the picture on this slide is adding a
universal extractant to soil samples.
a) What does it mean to “extract” a soil?
The process of briefly washing a specific quantity of soil in an extractant solution.
b) Discuss the pros and cons of using a universal extractant.
Analysis is cheaper and faster when one extractant (a universal extractant) is used to extract
all nutrients. Some predictive value is lost when using a universal extractant.

33. 33
By themselves,
extractable nutrient
levels are not
informative.
An experienced scout
knows how to integrate
an athlete’s 40 y dash
time with other
indicators to predict
ability to play the game
Likewise, an experienced
crop consultant knows
how to interpret soil test
results and integrate
them with other
information.
Discuss how the statement in the upper
left relates to the photo on this slide

34. 34
What is meant by the term
“soil test calibration”?
100 %
yield
Calibration is the process of
50 % figuring out how
yield extractable nutrient levels
relate to crop yield
Soil test P concentration (ppm)
http://www.ipm.iastate.edu/ipm/icm/2003/11-17-2003/mehlich3.gif

35. 35
Choose a lab and stick with it !
Discuss why the
above statement
is a good
strategy.
Labs use different analytical and interpretation methods. Evaluating
changes over time or differences between fields is difficult if the results do
not all come from the same lab

36. 36
a) Briefly explain the “sufficiency” approach for interpreting soil test
results. Use the term “critical level” in your answer.
The sufficiency approach uses soil test calibration to identify extractable nutrient levels
at which crops normally do not respond to additional fertilizer (aka critical levels).
b) Why do soil test critical levels vary from state to state?
Critical levels vary from state to state because of differences in soils, differences in
crops, differences in climate and differences in how conservative the scientists were
who interpreted the data from calibration experiments.

37. 37
How does a “build and maintenance” approach
differ from a strict sufficiency approach?
Strict sufficiency programs do not recommend
nutrient additions if soil test levels are above the
critical level. Build and maintenance programs
recommend maintenance applications unless soil
test levels are very high.
Critical Level

38. 38
Use the data on this slide to explain why a maintenance
approach for K is uncommon is some states in the High Plains.
Many soils in Nebraska and the Dakotas have such a high natural supply
of K that farmers rarely apply maintenance applications of K
http://soilfertility.unl.edu/Materials%20to%20include/2001%20NCR%20potassium_files/imag

39. 39
Changes in soil test results between 2001 and 2005
How is it possible for soil test K levels to go up when farmers are
harvesting more K than they are applying?
Its is thought that the increase in soil test K levels shown above (despite net withdrawals)
may result from reductions in tillage or depth of tillage leading to surface stratification of K.

40. 40
Why will it always be necessary to collect some soil samples?
Some day soon
soil testing
may consist mostly of
on-the-fly “sensing”
of soil hundreds to
thousands of times
per acre like a
yield monitor
Traditional soil sampling and analysis in a lab will still be needed to
calibrate and provide quality control for on-the-fly sensors.

41. Extra Credit
Answer honestly and thoughtfully
Did you the take this final independently and closed book?
Yes/No____________Signature _______________________
How did you prepare for the final exam?
If you submitted the alternative assignment (as opposed to
updating a 2008 Cover Crop Innovator profile), please explain
why it did not work out for you to update a Cover Crop
Innovator profile. (e.g., did you contact your innovator but
never hear back? did you wait until too late to contact your
innovator?, did your innovator say that nothing has changed?)

42. What do you think of power point slide based
quizzes/exams?
Do you think this class helped increase your
understanding of ideas that will be important in your
future? Explain.
Describe something that you learned in this class that you
think you will still remember in 3 years.
Identify a useful concept that you learned about in this
class that you think is probably poorly understood by
farmers/ag industry professionals. How would you explain
the concept to a farmer/ag industry professional?