Why cleaner air may be bad for your sourdough bread

Sulfur a toxic precipitation that is harmful to human health but helped crops and made for tastier bread

CHICAGO, US:

Less acid rain is good for the environment, but potentially bad for bread, cereals and pasta.

A decline in US power plant emissions over the last 30 years means the air has less sulfur, a crucial nutrient for wheat and many other crops that researchers are now working to replace with fertilizer applications.

For decades sulfur seeped into the soil via acid rain, a toxic precipitation that is harmful to human health but helped crops and made for tastier bread.

Bread’s delicious structure is mainly thanks to the gluten in wheat. Gluten gives bread its elastic nature and allows pizza dough to be stretched and tossed in the air. But gluten is held together by sulfur-to-sulfur bonds. Without enough sulfur, bread has a harder crust and poor crumb structure — resulting in something more like a brick than a baguette.

In Kansas, the sulfur deficit is plainly visible each spring as wheat plants in some areas emerge from their winter dormancy and resume growing. Most wheat fields are green, but some have a distinctive yellowish tint, the result of new leaves emerging from the tops of wheat plants low on sulfur.

European farmers have been applying sulfur for years, after research in the mid-2000s showed sulfur-deficient wheat when combined with other ingredients in baking can form acrylamide, a chemical linked to cancer.

In the United States, sulfur deficiency “is more of an emerging problem,” said Mary Guttieri, a US Department of Agriculture researcher who is studying sulfur and Kansas wheat. “It’s not been something that these farmers’ grandparents or even their parents needed to worry about.”

Adding sulfur on top of the common nitrogen, phosphorus and potassium fertilizers that US farmers have applied for years, is a boon to fertilizer companies, but raises costs for growers at a time commodity prices have slumped due to trade tensions with China and years of overproduction.

“The sulfur application is usually not cost-prohibitive, but because of the way the markets are going right now, any amount of increased cost is going to be scrutinised,” said Ron Olson, an agronomist with The Sulphur Institute.

Sales of fertilizer products containing sulfur are on the rise, manufacturers say. Demand for ammonium sulfate, for example, has grown by 5% annually in the last decade in Canada and the United States, according to Canadian fertilizer maker Nutrien Ltd.

Nutrien this week released a new fertilizer that combines elemental sulfur with phosphate.

“As the amount of atmospheric sulfur deposited via rainfall steadily declines, additional sulfur should be added to the soil through fertilizer applications,” Cristie Preston, Nutrien senior agronomist, said in a statement

With lockdowns due to the coronavirus curbing air pollution globally, sulfur deficiency could become even more acute in the US farm belt, soil scientists said, although the impact will likely pale in comparison to gradually reduced emissions over the last 30 years.