NEWS for North Dakotans
Agriculture Communication, North Dakota State University
7 Morrill Hall, Fargo, ND 58105-5665

September 9, 1999

NDSU Specialist: Postpone Sulfur Applications on Dormant-Seeded Canola until Spring

Canola producers who intend to plant their canola this fall should hold off on applying sulfur until next spring, says a soil scientist with the North Dakota State University Extension Service. And because of research results from NDSU and parallel studies in Canada, all canola producers may want to re-evaluate the form of sulfur they apply next year.

Application Options

"With spring-seeded canola, applying sulfur can be a tough problem. With dormant seeding, it's a tougher problem," says Dave Franzen, extension soil science specialist at NDSU. "If you put sulfur on in the fall, you're gambling that it's not going to leach. During the last few years, that gamble wouldn't have paid off."

For dormant-seeded canola, producers have several springtime application options. They can apply ammonium sulfate granules by ground before the crop emerges or early in the crop's growth stage, when stems are still flexible. Franzen says aerial application also works for granules.

"You're not going to get leaf burn from granules if the leaves are dry," Franzen says.

Similarly, spring-seeded canola can receive a broadcast application of ammonium sulfate before plants emerge. When seeding in the spring, canola producers also have the option of applying ammonium sulfate granules at planting time; however, the seed and fertilizer need to be separated by at least 1 inch. Franzen says a lateral placement of the granular fertilizer works best.

Another option for both dormant- and spring-seeded crops is to apply ammonium sulfate or ammonium thiosulfate in solution. Franzen says these liquid fertilizers should not go on the crop until there are at least five true leaves on the plants. He explains, "Leaf burn is reduced at this stage because the plant has been able to develop a waxy protective covering on the leaves."

The Data on Elemental Sulfur

The latest research studying the breakdown of elemental sulfur shows that the bacterial action required to transform this form of sulfur into sulfate is less effective than soil scientists previously thought.

"We knew that the transformation doesn't happen over the winter, but our latest data, based on four years of trials, shows us that it has a hard time happening even through the growing season," Franzen says. "Soluble sulfate sources are better than elemental sulfur sources, so we don't recommend elemental sulfur for either a fall or a spring application."

The key reason for the new NDSU recommendation is yield differences, as indicated by the following 1998 data involving spring applications of sulfur. The trial was conducted by NDSU researchers near Rock Lake, N.D.

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Source: Dave Franzen (701) 231-8884
Editor: Dean Hulse (701) 231-6136