SULPHUR in Agriculture
 

 

 

 


Which Crops Respond to SULPHUR?
  Yield responses to applied SULPHUR were first found on second-cut silage in the early 1980s.  Recently, responses have been found consistently in oilseed rape grown on light land, especially in East Angola and the southern countries.
In the past two years, yield increases have been found in winter wheat and first-cut silage.  Trial results go back to 1984 where responses were monitored on wheat, rape and silage from research funded by Hydro Agri.
Last year, yield responses from first-cut silage showed an average increase of 1.04 tons of dry material/ha, worth about L80/ha for a cost of L3-5/ha for SULPHUR.
Leaf tissue tests can give an accurate picture of SULPHUR availability and are best taken when crops are just coming into flower, because it is at this stage they will have taken up all their needs.  Current advice suggest supplementation is needed in oilseed rape if total content is below 0.4%.
For wheat, leaf samples should be taken on leaves two and three immediately below the flag.  SULPHUR deficiency is possible where the nitrogen:SULPHUR ratio is greater than 17:1, and SULPHUR content less than 0.12% in the dry matter of the grain or below 0.25% in leaf tissue.... total SULPHUR is below 0.25.
 
How to Check for SULPHUR Deficiency
 
Without adequate SULPHUR, crops cannot reach their full potential in terms of yield, quality or protein content. Nor can they make efficient use of applied nitrogen.

When fed to livestock, SULPHUR deficient forages can reduce animal performance.
With today's variety of fertilizers and application techniques, SULPHUR deficiency is easy to prevent and correct.  But it's not always easy to identify.
To prevent unexpected losses from SULPHUR deficiency, and to get an accurate reading of SULPHUR requirements, you'll need to check the following:
 
Develop a sharp eye
SULPHUR deficiency - like shortages of other nutrients - leaves its own distinct mark.  SULPHUR - deficient crops are typically small and spindly, with short and slender stalks.  New leaves turn yellowish - green in color, with even lighter - colored veins.
These symptoms can be easy to recognize -  if SULPHUR deficiency is the crop's only problem. Unfortunately, SULPHUR deficiency is often accompanied by shortages of other nutrients, which can mask these "text book" symptoms.
Other diagnostic measures will be needed to positively identify SULPHUR deficiency, but learning to recognize its symptoms will give you an edge and help reduce your losses.

Ask about soil tests for SULPHUR
 Like nitrogen, SULPHUR is a mobile nutrient that moves rapidly in the soil.  A soil test will therefore provide a general indication of your SULPHUR reserves, but the information gathered should only serve as a basis for your diagnosis.
Not all labs are equipped to test soils for SULPHUR, and those that are may do it by special request only.  Be sure to specify SULPHUR when sending in your samples.  Also, check with your soil lab for sampling guidelines, as they may want soil from various depths.  For example, 0 - 6 inches, 6 - 12 inches, 12 - 24 inches.

Plan on Plant Analysis
A plant analysis, or tissue test, is regarded as the most accurate means of measuring SULPHUR.  The information is especially useful when combined with soil-test results.
Agronomists generally recommend sampling plants early in the season so corrective measures can be taken.  Check with your testing lab for specific sampling procedures and timing.

Keep Tabs on N:S Ratios
Research shows that, for optimum performance and efficiency, plants should contain 1 part SULPHUR(S) for every 15-20 parts Nitrogen(N).  If the results of your plant analysis show a N:S ratio greater than 15:1, your crop could benefit from SULPHUR fertilization.
Likewise, if the N:S ratio is borderline, consider what it might be after you apply additional nitrogen - without SULPHUR.  University research shows that applying nitrogen alone can sometimes induce SULPHUR deficiency.

Evaluate Nitrogen Efficiency
Does your crop respond well to applied nitrogen?  If not, it could signal SULPHUR deficiency.  In one university field trial, a hay crop had failed to respond to 150 pounds N.  But when the same crop was fertilized with 33 pounds of SULPHUR, the crop yield nearly tripled.  Similar results have occurred on wheat, corn and canola.  Make sure your SULPHUR use keeps pace with your nitrogen rates.

Is Protein up to Par? 
SULPHUR plays an important role in protein synthesis.  If your grains and forages have been testing low in protein, your crops may not be getting enough SULPHUR.
A small investment is SULPHUR could have a dramatic impact on protein levels, while reducing your needs for expensive protein supplements.

Review Field History
High yields naturally remove high levels of SULPHUR from the soil.  If you've enjoyed bumper crops in recent years, your land could be on the verge of a SULPHUR shortage.

Scrutinize Fertilizer Records
Unlike the fertilizers used 10 - 20 years ago, today's popular, high-analysis grades of nitrogen, phosphorus and potassium do not contain significant amounts of SULPHUR.
If you've been fertilizing with such popular materials as urea, anhydrous ammonia, nitrogen solutions, tripplesuper phosphate, DAP or muriate of potash, your crops may not be getting as much SULPHUR as they did in previous years.

AssessAirQuality 
Pollution - control regulations have reduced SULPHUR-dioxide pollution by about 30 percent.  That's good news for the environment, but it also means that crops are getting less "free" SULPHUR from the atmosphere.  In high-yield situations, this can result in SULPHUR deficiency - even on farms near industrial areas.
Does your crop still get enough "free" SULPHUR to support your production goals?

Consider SoilType 
Traditionally, soils that are coarse in texture and/or low in organic matter are most susceptible to SULPHUR deficiency.  If your soils meet this description, the odds are good that your crops will benefit from SULPHUR fertilization - even if there are SULPHUR reserves beneath the sandy topsoil.  Traffic pans or soil acidity may prevent root penetration into the subsoil and reduce SULPHUR uptake.
Farmers with fine-textured, clay soils should also be careful, as intensive land use makes all crops vulnerable to SULPHUR deficiency.

Don't Over look Soil Temperature 
Cool soil temperatures can limit root development and reduce SULPHUR availability - even in heavy soils with rich SULPHUR reserves.
Whether topdressing a winter crop or just getting an early start on spring planting, always consider soil temperature and nutrient availability.  Conservation tillage situations can also produce cooler soils.  SULPHUR may be needed to stimulate early growth and nurse the crop through this stressful period.

Gauge Your Rainfall 
Like nitrogen, SULPHUR can be leached from the topsoil by heavy rains.  Irrigation can also carry SULPHUR beyond the reach of crop roots.
If your crop needs a mid-season application of nitrogen.  It also might benefit from SULPHUR.

Try a Test Plot 
You may not have the time or equipment to fuss with a scientific field trial, but leaving a check strip or putting out a few test plots will give you a glimpse of SULPHUR's impact on crop yield, quality and protein.
Before you start, check with your local crop specialist or fertilizer dealer about the difference between elemental and sulphate SULPHUR materials.  Using the right source at the right time will ensure best results.