A yellowing appearance to crop foliage and interveinal chlorosis are often signs of nitrogen deficiency. But, in some cases, these symptoms may be caused by a deficiency in another essential nutrient, sulfur.

“With the cars being cleaner and not as much coal being burned, we're not getting as much elemental sulfur out of the air as we used to, so we're starting to see deficiencies across the Midwest,” said Jeremy Stock, crop specialist at Prairieland FS.

While the Clean Air Act has resulted in lower atmospheric sulfur deposition rates, the regulations did as they were intended. This is beneficial to and supported by agriculture, but a crop's sulfur needs may now need to be addressed through an application.

With this type of deficiency in mind, a 2020 FS MiField Applied Research trial tested the response of soybeans to a sulfur application. For soybeans, sulfur is necessary for chlorophyll production, cell growth and development, carbon and nitrogen metabolism, and protein synthesis.

The trial took place on 32 acres farmed by Jon Webel near Perry, Illinois. One hundred pounds of ammonium sulfate was applied to 28 acres one week before planting, with four acres left as untreated test strips.

“There was an increase of seven bushels per acre,” said Webel. “And the soybeans looked better. They were taller and greener than the other [untreated] ones.” In addition to a yield bump, Webel also saw a high return on investment (ROI) on the application.

“At the time of harvest, soybean prices were around $10 per bushel,” said Stock. “It cost $25 per acre for the application, so with an increase of seven bushels an acre, the ROI was $45 per acre, on average.”

While Webel did see increased yield and ROI, tissue testing is recommended for confirmation before making a sulfur application, as symptoms are easily confused with other deficiencies.

“Farmers should look at their ground and soil tests and the price of commodities to see if a sulfur application is a viable option,” said Webel. “With the yield bump and the way prices are right now, it was a real big benefit for my operation.” To learn more, visit: https://www.fssystem.com.