Management of Soil Sulfur in the Atlantic Provinces
Crop Sulfur   Requirements		Sulfur (chemical symbol S) is a secondary plant macro-nutrient - it is required in relatively large amounts by plants, but it is not considered a fertilizer nutrient. Crop S requirements range from 5 to 30 kg S/ha-yr, comparable to phosphorus and magnesium requirements, but less than nitrogen, potassium and calcium. Certain crops, notably the crucifer (cole crops) and allium (onion) families, have high S-requirements and may benefit from supplemental S applications in some cases.
The soil S cycle:		Sulfur is an accessory element in rocks and minerals. It makes up about 1/20 of 1% of the minerals of the earth's surface. The soil mineral fraction usually contains a significant amount of S. Over time soil S tends to accumulate in soil organic matter. A mature soil usually holds most of its sulfur in organic form. This organic sulfur is gradually released in plant available form as the organic matter decays - a process known as "mineralization".
Sources of soil S:		In addition to soil organic & inorganic sources, there is S in air in the form of sulfur dioxide (SO2) gas from both natural and industrial sources. This gaseous S is carried into soil in rainfall (natural and acid rain). Plants and soil also absorb SO2 directly from the air ("dry deposition"). Manure from all farm livestock contains S and manure will replace losses of S. It is unlikely to encounter S deficiencies on soils that receive regular applications of manure. Some fertilizers contain S, but modern high analysis N-P-K fertilizers usually contain negligible amounts. S is quite mobile and water percolating through soil moves it below the root zone in humid climates.
Need for   additional S:		Soil S fertility has received little attention in Eastern Canada - native soil S, livestock manure and gaseous S have provided adequate amounts for most crops grown here. Cole crops (canola, cabbage, broccoli, cauliflower, brussel sprouts, radish) and onion crops may benefit from supplemental S in some soils. Crop response to supplemental S is most likely to occur on sandy soils low in organic matter.
S Fertilizers:		Supplemental S in the form of fertilizers can be used where deficiencies occur. Langbeinite and gypsum are the most commonly available materials. Sulfur fertilizers are listed below.
Symptoms:		Sulfur deficient plants have a thin spindly appearance and pale leaves, yellow in severe cases. This pale coloration is known as “chlorosis”. S is not very mobile within the plant so chlorosis appears in the newer leaves.
S deficiency vs. N deficiency		S deficiency symptoms are sometimes confused with nitrogen deficiency. The older leaves in sulfur-deficient plants may retain their green color while younger leaves show symptoms, whereas with nitrogen deficiency, the older leaves show the symptoms first. In cereal grains nitrogen deficiency shows up as chlorosis along the midrib of the leaves, whereas S deficiency affects the areas between the leaf veins.

Sulfur fertilizers	Chemical formula	S content	Comments	Cert. Organic Production
Langbeinite (0-0-22) (Sulfate of potash-magnesia)	K2SO4•2MgSO4	23% S	Highly soluble. Also contains 23% K2O & 11% Mg.	Approved
Agricultural Gypsum (Sulfate of lime)	CaSO4•2H2O	17% S	Most economic source of S. Sparingly soluble. Also contains 22% Ca.	Approved
Ammonium sulfate (20-0-0)	(NH4)2SO4	23% S	Highly soluble. Most acidifying N fertilizer, per kg of N.	Prohibited
Ordinary superphosphate (0-20-0)	Ca(H2PO4) + CaSO4	12% S	Also contains 20% P2O5 & 22% Ca. Not commonly available.	Prohibited
Sulfur coated urea (25-0-0 to 37-0-0)	NH2CONH2 + S	10-20% S	Slow release fertilizer. Very expensive. (Used exclusively on turf grass.)	Prohibited
Epsomite (Epsom salts)	MgSO4•7H2O	14% S	Highly soluble. Also contains 10% Mg. Not available in bulk quantities.	Approved
Elemental S ("Agri-Sul", "Flowers of sulfur")	S	90-95% S	Not recommended.	Approved

Diagnosis of   S deficiency:		Tissue testing as a diagnostic tool. Our soil tests analyze soil S, but do not report crop S requirements. The only way to tell if your crop needs S is by diagnosis of symptoms in the growing crop. These symptoms can be observed visually or by chemical analysis of plant tissue; the latter method, however, has not been studied sufficiently to give definitive diagnoses. Combining visual observations with plant tissue analysis will help to diagnose S deficiencies. Take separate plant samples from both good and bad areas within a field with suspected S deficiency. Each sample should consist of 10-20 plants. Analysis of soil samples from the same areas can help to confirm the diagnosis. (Plant tissue analysis and soil testing can be performed by Dept. of Agriculture labs in the Atlantic Provinces.) Comparison of S analyses between the different areas will indicate whether S-deficiency is the cause of the observed problem.
Correction of   S deficiency:		It is best to apply S requirements at, or before seeding, to avoid deficiency, but S deficiencies that are diagnosed after the crop emerges may be corrected by soluble S fertilizer if it is applied early in the growing season. Ammonium sulfate, langbeinite or epsomite are all suitable for for "rescue" applications of S. Rescue applications may be applied to soil as side dressing or top dressing at rates of 20 to 40 kg S/ha (85 to 170 kg ammonium sulfate or langbeinite per ha or 150 to 300 kg epsomite/ha)). Top dressing is effective only if the application is followed by rainfall or irrigation to move the S into the root zone.

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COMMENTS  ON  SULFUR  FERTILIZERS

Field Crop Fertilizers     (Available in this region, but not usually identified as S carriers.)
		Langbeinite (Sulfate of potash-magnesia, “Sul-Po-Mag”, “K-Mag” – 0-0-22) is a granular type potash fertilizer that also contains 23% S along with 22% K2O & 11% magnesium. It can be mixed with bulk N-P-K blends to supply all requirements in a single application. It is highly soluble and goes to work immediately. Langbeinite is a naturally occurring mineral salt and is approved for certified organic production.
		Agricultural Gypsum is a sparingly soluble mineral which also supplies calcium along with about 17% S. It is supplied as a powder and, therefore, it cannot be mixed into bulk fertilizer formulations. It should be worked into the soil with tillage before planting the crop to give it time to work. Fall application would be about as effective as spring. Higher S application rates should be used to compensate for lower solubility. It is the least expensive S fertilizer. Gyspum is approved for certified organic production.
		Ammonium sulfate (20-0-0) is a low analysis N fertilizer that contains 23% S in highly soluble form. (It produces the most soil acidity per kilogram N of any nitrogen fertilizer.) Ammonium sulfate is a granular type fertilizer suitable for blending with P & K fertilizers. Prohibited in Certified Organic Production.

Specialty S Fertilizers     ( not economic for use on field crops ).
		Ordinary superphosphate (O.S.P.), or Single Superphosphate (S.S.P), is not widely available in the Atlantic provinces. It is a lower analysis phosphorus fertilizer which contains about 12% S, in the form of gypsum. Like gypsum, it should be applied in spring and incorporated with tillage prior to seeding for best effect.
		Sulfur coated urea (SCU) is urea-nitrogen fertilizer covered with elemental sulfur (10-20% S). It is a slow release N fertilizer used in high value turf grass production. Its high price is prohibitive for field crop production.
		Epsomite, (14% S) is not available in quantities large enough for farm production. Home gardeners can obtain sufficient quantities in the form of "Epsom Salt" sold as bath salts at pharmacies. Epsomite is a highly soluble salt suitable for either surface application or incorporation.
		Elemental sulfur, sold as "Agri-Sul", and "Flowers of Sulfur" (about 90% S) can lower the soil pH into the extremely acid range, making the soil unsuitable for any crop; however, it is safe when used as a fertilizer at rates below 100 kg/ha. Elemental S must be oxidized before it can be taken up by plants. The time required for S oxidation varies widely, depending on soil conditions and size of the particles. Elemental S is a less reliable source of S fertility than the other fertilizers described above.