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Research: Sulfate of potash increases sweet potato yields

University studies sponsored by Great Salt Lake Minerals Corporation (GSL), North America's largest producer of sulfate of potash (SOP), indicate that sulfate of potash may be a more effective potassium fertilizer for sweet potato crops than traditional muriate of potash (MOP), increasing the yield of U.S. No. 1 sweet potatoes by as much as 32 percent in preliminary studies.

Ongoing crop trials at LSU AgCenter compared the effect of different sources of potassium fertilizer on the yield and quality of sweet potatoes. Preliminary results of the studies indicate that sulfate of potash positively affects sweet potato yields in Louisiana, according to a GSL press release.

In the crop trials, SOP treatments produced more bushels per acre of sweet potatoes and more U.S. No. 1s than treatments of MOP — a difference that is economically significant to sweet potato producers, GSL reported.

Additional sweet potato trials are under way with the University of California, Davis, and North Carolina State University.

Results of the Louisiana test show that the increased yield of U.S. No. 1s from the SOP-treated fields would produce additional revenue of approximately $1,400 per acre based on an average market price of $15 per 40-pound box of U.S. No. 1 sweet potatoes, GSL reported.

“Sulfate of potash gives sweet potato plants what we're calling a triple advantage — high potassium, low chloride and readily available sulfur,” said Jack Novacek, director of sales and marketing, Great Salt Lake Minerals.

“Under many soil conditions, SOP provides an efficient source of nutrients for sweet potato plants and other crops without excess chloride.

“Ultimately, this increases the possibility for higher yields and therefore greater profits for growers.”

Sulfate of potash, also known as the compound K2SO4, is a high potassium source.

Potassium is an important factor in plant growth and overall health, promoting efficient uptake of water and helping plants to resist the harmful effects of drought, temperature extremes and other stresses.

With 17 percent sulfur in plant-readily available sulfate form, sulfate of potash helps sweet potato plants photosynthesize and produce chlorophyll, proteins and amino acids.

Growth-promoting sulfate is critical for young plants and cannot be found in MOP fertilizers, GSL reported.

Sulfate of potash also has the lowest chloride content compared to other potassium fertilizers. GSL's sulfate of potash has less than 1 percent chloride.

Sulfate of potash delivers the potassium sweet potato plants need without the harmful effects that excess chloride has on this chloride-sensitive crop.

SOP from Great Salt Lake Minerals is available in various particle sizes to meet different application needs and comes in bags or in bulk via truck and rail.

GSL also offers an organic SOP that is listed as an approved source for potassium and sulfur by the Organic Materials Review Institute (OMRI).

For more information on GSL and the company's sulfate of potash products for sweet potatoes, go to or call (800) 551-8216.

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