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Mar 30, 2024

Yellowing, streaking growth a sign of sulfur deficiency

FARGO, N.D. — For fertilizer , farmers usually think about N, P and K, but they also may be lacking in S, for sulfur. “Our focus for fertilizer has long been NPK — nitrogen, phosphate and potassium —

FARGO, N.D. — For fertilizer , farmers usually think about N, P and K, but they also may be lacking in S, for sulfur.

“Our focus for fertilizer has long been NPK — nitrogen, phosphate and potassium — but now we’re learning ... that sulfur is the fourth macronutrient and that growers are needing to reevaluate their fertility plans,” said Karl Wyant director of agronomy at Nutrien, a fertilizer company based in Canada.

Wyant was in Fargo, North Dakota, for the June 8 Cultivate conference, educating the agriculture industry on the need for sulfur and how to diagnose it.

“As the new growth comes up, the crop starts to turn yellow because it doesn’t have sulfur to make the chlorophyll,” Wyant said. “So you see that yellowing, that’s generally the first sign a grower would see.”

But farmers can still head off yield loss, which Purdue University research says can be as much as 11 bushels per acre in corn.

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“If you’re in season, if your corn is yellow, you’re going to want to apply an immediately available sulfur form, that’s usually looking for a product that has the word ‘sulphate’ in it. … The sulphate can be immediately used by the plant,” Wyant said.

The difference between a Nitrogen (left) and Sulfur (right) deficiency in corn is where the symptoms are located:N: pale green or yellowing of LOWER leaves, occurring in a V-shape on the leafS: pale green or yellowing of UPPER leaves, sometimes with interveinal striping pic.twitter.com/TBaiQTRj2M

While sulfate is a short-term fix, farmers might also need to address sulfur long-term, applying elemental sulfur, which needs more time to be effective, with their fall fertilizer applications.

“To build that savings account for spring, so it’s not such a reactionary approach,” Wyant said.

Sulfur deficiency is a relatively recent problem. North Dakota State University put out its first sulfur deficiency advisory in 2015.

Wyant jokingly blames former President Richard Nixon.

“The last five to 10 years, sulfur’s jumped on a lot of growers’ radars, that’s because we cleaned a lot of the sulfur out of the air,” Wyant said.

“Thanks to the 1970 Clean Air Act that Nixon signed, we’re scrubbing a lot of the sulfur out of the coal plants and other pollution sources.

“So on the good side, we have less sulfur pollution, we have less acid rain. But in terms of your growers, you’re getting less free sulfur that’s coming back down to the ground as a free fertilizer source.”

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Sulfur deficiency affects crops other than corn, too, such as soybeans, wheat and sugarbeets .

Sulfur deficiency is most common in ground that has sandier soil and is prone to leaching or is lower in organic matter.

“One piece that can drive deficiency are some of these large rainstorms we’ve had recently where that rainfall can actually push the sulfur below the root zone so the crop can’t get it,” Wyant said.

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