N K Ca Mg P S

macronutrients micronutrients air & water

Soil

~ 9 micronutrients are essential for all plants… identify 6!

C O H ??????????

Na Si

V

Needed by some plants

0.1%

Many more elements are found in plants – some of which can have beneficial (but not yet

proven essential) effects on plant growth

of plant dry matter

1

The following micronutrients are currently recognized as essential for the growth of all plants: Cl Fe Mn Zn B Cu Mo Ni Co

a) b)

Which of the following crop response curves is most appropriate for a macronutrient? How about a micronutrient? Explain your selections.

2

mac

ron

utr

ien

ts

mic

ron

utr

ien

ts

Macronutrients have broad sufficiency ranges. In contrast, micronutrients tend to have narrow sufficiency ranges and

care should be taken to avoid overapplication/toxicity.

Identify 2 similarities and 2 differences between the

N and S cycles

3

Similarities with the N cycle

• Many oxidation states

• Most of the S in soil is a component of SOM

• Biological transformations are important e.g., mineralization and immobilization

• Volatilization is a major loss pathway

Differences with the N cycle

• Very little S in the earth’s atmosphere naturally (most of the S in the atmosphere today is anthropogenic)

• Weathering of rocks is the primary source of S

• Most global S in the earth’s crust

• Soil concentrations range from 10s to 1000s of ppm (as compared to 100s to > 10,000 ppm N)

Identify 2 reasons why S deficiencies are increasingly

common in the Midwest

4

- 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.

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

5

Material S content lbs to supply

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

Why is it a standard practice for

orchardists to apply foliar fertilizers

containing calcium?

6

Calcium deficiencies are common in orchard crops and fruit quality is often improved by

foliar applications of Ca

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

7

I am an enzyme

Generally speaking what types of nutrient deficiencies show up on upper leaves? What about lower leaves? Explain your answer.

8

Micro/secondary nutrients Macronutrients

mobile within plants Limited movement within plants

Micronutrients deficiencies are normally associated with one or more of the following five situations:

9

(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.

a) Which micronutrient appears to be most affected by

glyphosate?

b) When is glyphosate application most likely to result in yield loss?

10

Mn

Yield loss is most likely when crop uptake of Mn would be borderline w/o glyphosate

Some evidence suggests that crop seeds are increasingly likely to be low in Mo

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.

11

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."

In Illinois

A = boron and b = molybdenum.

12

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.

13

Biofortification

(breeding for higher nutrient levels in crops) NOT a silver bullet,

but an additional weapon to fight deficiency

Biofortification

Identify 2 other

strategies

14

Supplementation Commercial

Fortification

Dietary

Diversity

Chloride

According to the U of I, chloride (Cl) deficiency has not been observed and is unlikely to be observed in IL.

There is no reliable soil test for Cl in Illinois.

Why is chloride deficiency so unlikely in IL ?

15

Most IL farmers routinely apply “potash” aka muriate of potash (KCl) Cl makes up ~ 48 % of the mass of “potash”

The acid infertility complex

What is meant by the term in the center of this slide?

16

The collective challenges faced by crops growing in acid soils

http://www.farmtested.com/research_pp.html

most

^

Which micronutrient becomes more available as pH increases? 17

Mo = molybdenum

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

18

Aluminum toxicity

A coffee urn model is commonly used to represent active and reserve acidity in soil. Do you think this

model is informative? Briefly explain.

19

Reserve acidity

acti

ve a

cid

ity

Reserve acidity is the primary supply

of acidity in soil and can quickly

resupply the active acidity (pH is a

measure of active acidity).

Lime requirement can not be accurately estimated based

on just the current pH. Some

measure of the reserve acidity is

also needed.

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

20

http://departments.agri.huji.ac.il/plantscience/topics_irrigation/uzifert/4thmeet.htm

Which plants received nitrate (NO3-)?

Which plants received ammonium (NH4+)?

Briefly explain your

answer

A B

21

A = nitrate

B = ammonium

Uptake of nitrate causes plant roots to

release alkalinity whereas uptake of

ammonium causes plant

roots to release acidity.

Roots need to maintain charge

balance

What happens to the acidity and alkalinity in plant biomass when it is burned?

Oxides of Ca, Mg and K

Oxides of C, N and S

22

Acidity Alkalinity

Identify 1 thing farmers can do to reduce the rate of soil acidification other than adding lime.

23

Farmers can reduce the rate of acidification by using N fertilizers that are less acidifying AND by using practices that reduce nitrate leaching

The amount of lime needed to bring about a 1 unit change in pH varies

widely between soils

WHY?

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)

“Illinois method” of determining lime requirement

http://iah.aces.uiuc.edu/pdf/Agronomy_HB/11chapter.pdf

Recommend a lime rate for the following scenario

Soil belongs to the lime group with highest

reserve acidity

Initial pH is 5.0

25

8 tons/ac

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.

26

Goals of routine soil testing

rapid

cheap

predictive

broadly applicable

Identify 3 of the 4 goals we discussed in class

27

What is a composite sample ?

120 acre field

The U of Illinois currently recommends collecting

1 composite sample per 2.5-acres.

28

A composite sample is a mixture

of multiple (typically 5-10)

sub-samples

Soil management zones

Soil 1

Soil 2

Soil 3

Soil 4

Briefly describe and differentiate between the management zone

and the grid sampling approaches for soil sampling.

What is needed to make the management approach a

reasonable approach?

29

Grid sampling involves a uniform pattern of high density sample collection (frequently 1 composite sample per 1-2.5 acres)

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.

The management zone sampling approach requires that you have enough understanding of soil variation to designate appropriate zones.

Late summer and fall are often recommended as the best times for collecting soil samples

Provide at least 2 reasons why.

30

- 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

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.

31

Temperature, moisture, microbial activity, rooting depth, root health, crop genetics…

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?

b) Discuss the pros and cons of using a universal extractant.

32

The process of briefly washing a specific quantity of soil in an extractant solution.

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.

By themselves, extractable nutrient

levels are not informative.

Discuss how the statement in the upper left relates to the photo on this slide

33

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.

What is meant by the term “soil test calibration”?

100 % yield

50 % yield

http://www.ipm.iastate.edu/ipm/icm/2003/11-17-2003/mehlich3.gif

Soil test P concentration (ppm)

34

Calibration is the process of figuring out how

extractable nutrient levels relate to crop yield

Choose a lab and stick with it !

Discuss why the above statement

is a good strategy.

35

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

a) Briefly explain the “sufficiency” approach for interpreting soil test results. Use the term “critical level” in your answer.

b) Why do soil test critical levels vary from state to state?

36

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).

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.

Critical Level

How does a “build and maintenance” approach differ from a strict sufficiency approach?

37

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.

Use the data on this slide to explain why a maintenance approach for K is uncommon is some states in the High Plains.

http://soilfertility.unl.edu/Materials%20to%20include/2001%20NCR%20potassium_files/image008.gif

38

Many soils in Nebraska and the Dakotas have such a high natural supply of K that farmers rarely apply maintenance applications of K

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?

39

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.

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

Why will it always be necessary to collect some soil samples?

40

Traditional soil sampling and analysis in a lab will still be needed to calibrate and provide quality control for on-the-fly sensors.

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?)

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?