Sulfur Applications in Western Canada
Robert Mullen, Ph.D.
Director of Agronomy
To say Dr. Robert Mullen is passionate about agriculture would be an understatement. He holds a Bachelor of Science degree in ag business from Cameron University, along with a Master of Science degree in plant and soil science and a Ph.D. in soil science from Oklahoma State University. In addition, Dr. Mullen has been published in a variety of scientific and trade journals. But it’s not just his academic accomplishments that make him unique. It’s his unwavering ability to take complex data and — in simple terms — explain how it impacts a farmer’s bottom line. Dr. Mullen delivers the kind of insightful observations that can lead to a more profitable business. As a leading agronomy expert, Dr. Mullen has a goal to further educate farmers on best management practices that improve their yields and maximize their return on investment.
A major consideration with regard to 4R nutrient stewardship is: When is the best time to supply nutrients? And as one can imagine, it depends upon what nutrient is being considered, and the prevailing weather/soil conditions that may affect nutrient transport (or loss potential). Here, we will briefly focus on sulfur application in Western Canada.
The predominant forms of sulfur are salt forms (ammonium sulfate or gypsum – calcium sulfate) or elemental sulfur (bentonite products). Ammonium sulfate or gypsum are sources of readily available sulfur, and elemental sulfur is a slower release form that requires biological oxidation to supply sulfur (speed of oxidation is dictated primarily by particle size and soil temperature).
Recognize that sulfate is a mobile nutrient within the soil, so fall applications of sulfate salt forms in higher rainfall environments (even worse with coarse textured/sandy soils) can be conducive to loss. That being said, rainfall amounts in Western Canada tend to be low enough across most of the Prairie Provinces that loss of fall applied sulfate is relatively low (there are wet areas where these applications can be more susceptible for loss). Therefore, fall application of sulfur fertilizers can be a good way to supply sulfur in Western Canada.