Since 2017, Dr. Zack Ogles, manager of agronomy, at Tessenderlo Kerley, has been trying to understand how applications of thiosulfate can inhibit nitrification when applied with a UAN.
In other words, by adding thiosulfate, increasing the sulfur rate slightly or making a slightly different application method, could one fertilizer benefit the other? Could 1 plus 1 equal 3?
Ogles says yes, as well as a recently published paper in the Soil Science Society of America Journal, which recaps the test results. Thiosulfates not only supply sulfur but also significantly reduce nitrogen loss by slowing the conversion of ammonium to nitrate in the soil.
"We're improving outcomes on multiple levels," Ogles says. "By delivering both sulfur and nitrogen protection in a single application, these products help growers maximize return on investment while advancing sustainable farming practices."
The light bulb moment.
Ammonium thiosulfate (ATS and sold under the brand Thio-Sul) and potassium thiosulfate (KTS) are used in liquid formulations, and typically, ATS is applied in a blend with urea ammonium nitrate (UAN) for a 28-0-0-5(S) fertilizer analysis.
Ogles says prior to the confirmation provided by the laboratory study as well as in-field research, agronomists had recognized the potential for thiosulfate to provide a similar benefit as Dicyandiamide (DCD), a commonly used nitrogen stabilizer.
"Both Thio-Sul and KTS were shown to inhibit nitrification comparable to DCD, in the three soils used in the published research. Additional studies are needed to fully understand how thiosulfates perform in a broader range of soil types and conditions," he says. "Prior to this research, thiosulfates were often regarded as weaker nitrification inhibitors and with limited effect. But what we discovered in this study was that at the rate thiosulfates are being applied today, we're seeing effects equal to, or even greater than commercially available nitrification inhibitors."
Ogles says with the increased focused of sulfur as the "fourth major nutrient," and most crops requiring sulfur fertility, a banded/concentrated application of thiosulfate applied at the time of planting brings a new agronomic opportunity.
"The big advantage is that you can use a fertilizer to help improve the efficiency of nitrogen," he says. "In other words, using a thiosulfate fertilizer with these enhanced properties helps improve the effectiveness of the nitrogen that's being applied."
The laboratory trials explained in the recently published paper include studies across soil different soil types, which were brought in from California, Iowa and Alabama– Marvyn loamy sand, Tujunga loamy sand, and Sable silt loam.
The trial applied urea solution along with between 15 and 30 pounds of sulfur in the form of ammonium thiosulfate or potassium thiosulfate.
