“When its called a secondary nutrient, it annoys me as high yields of good quality produce are only possible when there is sufficient S in the soil,” said Graeme Blair.

“It’s certainly a macro, rather than micronutrient.”

Speaking at Incitec Pivot’s recent Victorian Agronomy Community conference, Dr Blair said that certain food crops had a higher need for sulphur than others.

In terms of the Australian broadacre cropping industry, canola is the one that needs the most, although cotton also needs a reasonable bank of S to do well.

And application time is also crucial.

“With canola, it doesn’t need much as a seedling, but needs it later on in the growing season, whereas cotton does not need it at flowering, but rather earlier on.

“So an early application of S would be good for cotton, but not so good for canola.”

He said growers needed to work on getting the balance between nitrogen and sulphur right if they were to get the best out of their crops.

For example, in canola, he said while nitrogen boosted yields, without sufficient sulphur, oil levels would suffer.

Dr Blair said one critical factor growers had to be aware of was how quickly paddocks can become sulphur deficient.

“We’ve seen growers who have switched to phosphate fertilisers without any sulphur and they have quickly become sulphur deficient.

Gypsum is one good way to replace sulphur levels, however as a low analysis product it can be costly to move.

He said research was showing the best way to apply sulphur was a mixture between sulphur in a sulphate form, as in many fertilisers, and in elemental form.

“When you mix it up, you can get both good results early in the year and also some late release, the sulphate being released earlier, and the elemental S becoming available later in the season.”

“The take-home message is that sulphur ain’t sulphur and a mixture of sources is usually the best.”