This is a slightly updated version of the slides on S that I shared with my Soil Fertility class in fall 2010

1. Sulfur has an atomic weight of 32.06
4 rare isotopes 33S, 34S, 35S and 36S can be used for tracing.

2. . . . sulfur is a devilish substance . . . Discharged from the bowels of the earth,
by volcanoes or evil-smelling hot springs . . . Surely the effluent of Hell itself.
– J.R. Postgate

3. Why is S important ?
• Essential element required in relatively high
concentrations
• Essential component of 3 amino acids
– cysteine, cystine, methionine
• Disulfide bonds give structure to many proteins
• Source of metabolic energy for many bacteria
• Postive and negative environmental impacts
– Macronutrient
– Acid mine drainage, acidic deposition

4. The S cycle is complex

5. 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

6. Differences with the N cycle
Not much S in the earth’s atmosphere naturally
(most of the S in the atmosphere today is anthropogenic)
Weathering of rocks is the primary source
Most global S in the earth’s crust
Soil concentrations range from 10s to 1000s of ppm

7. Sulfur Forms in Soils
• Inorganic S
– Sulfate dominates (SO42-)
– Sulfides (S-2, flooded conditions)
– Elemental S
– Thiosulfates (S2O32-)
– Range in oxidation states (-2 to +6)
• > 90% of total S in most soils is organic

8. S has lots of oxidation states
Sulfides, -2 Sulfide ion S2-, bisulfide ion
HS-, hydrogen sulfide H2S,
carbon-bonded S
Polysulfide, -1 Disulfide ion S22-, pyrite
(FeS2)
Elemental S S0
Thiosulfate, -2 & +6 Thiosulfate ion S2O32-
Sulfites, +4 Sulfite ion SO32-, sulfur
dioxide SO2
Sulfate, +6 Sulfate ion SO42-, sulfuric acid
H2SO4

9. There are many volatile biogenic S compounds
Compound Formula Atmospheric Production
concentration (Tg y-1)
Hydrogen sulfide H2S 0.2 – 1 ppb 16.5 – 70.6
Sulfur dioxide SO2 0.2 – 5 ppb 15.0
Carbon disulfide CS2 0.1 – 0.4 ppb 3.8 – 4.7
Carbonyl sulfide COS 0.2 – 0.6 ppb 2.7 – 3.5
Methyl mercaptan CH3SH
Ethyl mercaptan CH3CH2SH
Dimethyl sulfide CH3SCH3 58 ppt 39.6 – 45.4
Dimethyl disulfide CH3SSCH3 1.3 – 3.4
"smell of the sea"

10. Is S a limiting nutrient ?

11. Sulfur deficiencies are increasingly common
- 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.

12. http://www.mitchellfarms.com/?p=84

13. Wet and dry S deposition is monitored throughout the US
http://www2.nature.nps.gov/air/Monitoring/drymon.cfm

15. Sulfur emissions in Wisconsin over the last 2 decades
Why did this happen?

16. The Cap and Trade Success Story
"Cap and trade" harnesses the forces of markets to
achieve cost-effective environmental protection. Markets
can achieve superior environmental protection by giving
businesses both flexibility and a direct financial incentive
to find faster, cheaper and more innovative ways to
reduce pollution.
Cap and trade was designed, tested and proven here
in the United States, as a program within the 1990 Clean
Air Act Amendments. The success of this program led
The Economist magazine to crown it "probably the
greatest green success story of the past decade."
(July 6, 2002).

18. Interpreting soil test S in Illinois
Soil test S (lbs/A) RATING
0 - 12 Very low
12 - 22 Low
Response
> 22
unlikely

19. The IL Agronomy Handbook has long stated that
IL crops are unlikely to be deficient in S.
Experiments conducted across Illinois in the late
70s only identified a response to sulfur at
5 out of 82 site-years.
Correlation between yield increases and measured
S levels was low, indicating that soil test S does
not reliably predict sulfur need.
When soil test S levels are above 22 lbs /acre, it is
very unlikely that a response to applied S will occur.
When soil test S levels are below 22 lbs/acre,
response to applied S is more likely
(but not predictable).

20. It is high time for some more sulfur research in IL!

21. Recent S research in Central and Northeast IA
The average yield response to S application (for the 6 out of 10 sites with a
response) was 9 bu/acre, with a range of 5 to 13 bu/acre. The yield
increases were large enough to pay for the recommended S application
(15 lb S/acre for fine‐textured soils and 25 lb S/acre for coarse‐textured soils).

22. Sulfur Deficiency in Corn
Unlike N,
S is not
readily
Overall light green
remobilized color, worse on new
from older to leaves during rapid
younger growth.
plant parts.

23. Sulfur Deficiency in Wheat
Overall light green color, worse on
new leaves during rapid growth.

24. http://landresources.montana.edu/SoilFertility/Images/S/Alfalfa-S-deficiency.jpg
Alfalfa is the crop most likely to respond to sulfur (S)
application in Illinois.
Corn has only been shown to respond in a few experiments,
primarily in northwestern Illinois.
Organic matter is the primary source of sulfur in soils, so
soils low in organic matter are more likely to be deficient
than soils high in organic matter.
S deficiency is most likely on sandy soils.

25. Important S concepts
When S is deficient, plants tend to accumulate non-protein N,
which raises the N/S ratio in the plant. A N/S ratio of 9:1 to
12:1 is especially important in forages that will be used for
animal feed, so that the rumen microorganisms can
effectively use the N.
Grasses are more able to utilize sulfate (SO42-) than legumes,
grasses will tend to crowd out the legumes in S deficient
pastures. Rhizobia need S to fix N.
Some plants, like mustard and onion, get their smell and
taste from the presence of S compounds.

26. Sulfur is a key factor limiting the amount of
corn by-products that can be fed to cattle.
Sulfur levels of most corn by-products can range from 0.4 to 0.9% S on
a dry matter basis. Some liquid by-products have been tested as high as
1.5 to 2% S. Sulfur is added during both the wet and dry corn milling
process, so the by-products contain additional levels above that
concentrated from the original corn.
Although it is based on limited research in cattle, the NRC recommends
a maximum tolerable level of 0.4% of the ration dry matter for sulfur in
the ration. Using that recommendation as a guide the maximum level of
corn by-products would range from 30% of dry matter intake at high
sulfur levels to over 70% at low levels, based strictly on the S content

28. So how many lbs of ammonium sulfate should be
applied if your goal is 10 lbs of S?
So what can you apply if your soil needs S?
Ammonium sulfate (21-0-0) ?
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 – 100% S (ES95, ES90, ES85)
Animal manures – 0.1-0.3% of DM
What is the sulfur content of ammonium sulfate?
Chemical formula = (NH4)2SO4
Molecular weight = 132.1 g/mol
Atomic weight of S = 32.1 g/mol
32.1/132.1*100 = 24% S

29. Example of an elemental S product
?

30. Some elemental S products degrade more rapidly

31. When mixed with other fluid
fertilizers and applied as a
concentrated band, ATS can
enhance micronutrient
availability, inhibit urease
activity, inhibit nitrification and
improve availability of P
ATS is a weak inhibitor compared
to N-Serve and Agrotain