HGCA has released a new sulphur (S) publication to help growers get S levels back on track.

Based on the latest research, Information Sheet 28 can be downloaded from the HGCA website.

Over the last 45 years, ‘free’ sulphur deposits from the atmosphere have declined significantly due to reduced industrial pollution. Current deposition is estimated to be only 10% of 1980’s levels.

As soils store very little S, particularly on chalky or sandy soils, many more growers now need to consider making regular S applications.

However, the 2012 HGCA/Defra yield plateau project found strong evidence that S application in many wheat and oilseed rape crops could be improved.

The new publication includes data from two recently completed projects that looked at both supply and demand of this essential nutrient.

The first project investigated how sulphur levels impact on cereal quality.

James Holmes, HGCA Research and Knowledge Transfer Manager, said: “We know crop S requirements need to be met for a good loaf volume. But our new work shows S-deficiency can also be linked to higher levels of the processing contaminant acrylamide.”

Wheat trials, conducted on sandy soils highly likely to be responsive to S application, showed a clear and significant effect of S application in reducing the acrylamide-forming potential of wheat in five of the six trials.

Rothamsted Research, which conducted the work, concluded that 50kg SO₃/ha should always be applied in spring to wheat at responsive sites.

A second study, led by ADAS, looked to clarify S supply from organic materials, such as manures, slurries and biosolids.

“Organic materials contain useful supplies of S. These supplies are either readily available to the crop or locked up until mineralised.

“As the Fertiliser Manual (RB209) does not provide sufficient guidance on the S value of organic materials, HGCA commissioned this research to help growers get a better handle on the use of organic fertiliser sources of S,” said Mr Holmes.

On average, total S content of organic materials generally showed good agreement with the ‘typical’ values given in RB209, although biosolids tended to have a higher S content.

Nutrient analysis revealed the amount of S available to crops was dependent on the type of organic material. When applied in spring, available S varied from around 15% of total S for cattle farmyard manures to 60% of total S for broiler litter.

When applied in autumn, crop availability was reduced and more variable, due to overwinter rainfall causing leaching.

“It is important to remember that organic materials are highly variable and it is advisable to send a representative sample for analysis to help ensure that S targets are met,” concluded Mr Holmes.