Sulfur has an atomic weight of 32.064 rare isotopes 33S, 34S, 35S and 36S can be used for tracing.
. . . 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
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
Similarities with the N cycleMany oxidation statesMost of the S in soil is a component of SOMBiological transformations are importante.g., mineralization and immobilizationVolatilization is a major loss pathway
Differences with the N cycleNot much S in the earth’s atmosphere naturally(most of the S in the atmosphere today is anthropogenic)Weathering of rocks is the primary sourceMost global S in the earth’s crustSoil concentrations range from 10s to 1000s of ppm
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
S has lots of oxidation statesSulfides, -2 Sulfide ion S2-, bisulfide ion HS-, hydrogen sulfide H2S, carbon-bonded SPolysulfide, -1 Disulfide ion S22-, pyrite (FeS2)Elemental S S0Thiosulfate, -2 & +6 Thiosulfate ion S2O32-Sulfites, +4 Sulfite ion SO32-, sulfur dioxide SO2Sulfate, +6 Sulfate ion SO42-, sulfuric acid H2SO4
There are many volatile biogenic S compoundsCompound Formula Atmospheric Production concentration (Tg y-1)Hydrogen sulfide H2S 0.2 – 1 ppb 16.5 – 70.6Sulfur dioxide SO2 0.2 – 5 ppb 15.0Carbon disulfide CS2 0.1 – 0.4 ppb 3.8 – 4.7Carbonyl sulfide COS 0.2 – 0.6 ppb 2.7 – 3.5Methyl mercaptan CH3SHEthyl mercaptan CH3CH2SHDimethyl sulfide CH3SCH3 58 ppt 39.6 – 45.4Dimethyl disulfide CH3SSCH3 1.3 – 3.4"smell of the sea"
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.
Wet and dry S deposition is monitored throughout the US http://www2.nature.nps.gov/air/Monitoring/drymon.cfm
Sulfur emissions in Wisconsin over the last 2 decades Why did this happen?
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Interpreting soil test S in Illinois Soil test S (lbs/A) RATING 0 - 12 Very low 12 - 22 Low Response > 22 unlikely
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 measuredS 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 isvery 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).
It is high time for some more sulfur research in IL!
Recent S research in Central and Northeast IAThe 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).
Sulfur Deficiency in Corn Unlike N, S is not readily Overall light green remobilized color, worse on newfrom older to leaves during rapid younger growth. plant parts.
Sulfur Deficiency in Wheat Overall light green color, worse on new leaves during rapid growth.
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.
Important S conceptsWhen 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.
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 ona 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 inthe 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
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 DMWhat 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
Some elemental S products degrade more rapidly
When mixed with other fluid fertilizers and applied as a concentrated band, ATS can enhance micronutrient availability, inhibit ureaseactivity, inhibit nitrification and improve availability of P ATS is a weak inhibitor compared to N-Serve and Agrotain