Ask an Agronomist: Why Sulfur?

Learn how and why sulfur should be effectively integrated into a fertility program to boost yield and quality

September 5, 2022
5 mins
Jason Haegele, Ph. D

Every acre counts when it comes to the return on investment for crop nutrition and fertilizer programs. With increased focus on soil health, environmental impact, and nutrient innovation, the nutrients and products we focus our dollars on become increasingly importantWe asked ICL’s agronomist some quick questions about major fertility trends and new opportunities for optimizing crop production profitably. Here’s the dirt. 

Ask An Agronomist: Why Sulfur? 

The Agronomist  

Jason Haegele, North American Agronomy Lead 

Jason Haegele leads ICL’s research collaborations with universities and third-party research contractors in North America to demonstrate the efficacy of ICL products on a broad range of row crops and specialty crops. He is a graduate of the University of Illinois and Iowa State University and has a broad range of experience in applied research and field sales support for plant nutrition, adjuvants, crop protection, and biological products. 

What is sulfur and why is it important? 

Sulfur is often overshadowed by N, P, and K, but it’s a powerhouse macro nutrient, and a limiting factor in crop yield and quality. Sulfur for crop nutrition can come from soil organic matter, irrigation water, or common fertilizer sources including ammonium sulfate and potassium sulfate. From a fertility standpoint, it is a building block of plant proteins, and can impact nitrogen use efficiency, photosynthesis, and protein content of grain or other forms of harvested crop produce. 

Why are we seeing an increased interest in sulfur? 

For years, sulfur deficiency wasn’t a top concern for many growers as mineralized organic matter and high sulfur emissions supplied more than enough to meet crop needs. In the last 30 years reduced sulfur emissions have substantially decreased atmospheric sulfur availability in North America. In combination with greater crop productivity, which increases the uptake and removal of sulfur with the harvested crop, visual and hidden sulfur deficiencies are becoming more common in many areas. 

Elemental vs sulfate-based sulfur: does it impact ROI? 

Elemental sulfur is one possible source for applying fertilizer-based sulfur. This form, however, must be oxidized to become crop available and this process can be slow and unpredictable. Sulfate-based forms are more readily available to the crop, but also prone to leaching in high rainfall environments. Newer fertilizer sources which contain sulfate, but have a more gradual release pattern, may be better suited for promoting nutrient availability exactly when the crop needs it, and in turn, increasing ROI to the grower. 

We’ve been hearing a lot about polyhalite as a sulfur source. What is it? 

Polyhalite is a naturally mined mineral containing potassium, sulfur, calcium, and magnesium. It is exclusively sold by ICL under the name Polysulphate. It caught my attention because of its relatively high sulfur content (19.2% for granular Polysulphate), gradual release pattern, and other favorable characteristics like low chloride and salt index. For growers this means it’s a 4-in-1 nutrient that addresses the need for sulfur as well as supplying other important macronutrients like potassium, calcium, and magnesium. 

What can farmers do to prevail over high fertilizer prices?  

Agricultural producers have a lot of great tools to optimize nutrient applications. These include traditional soil testing, tissue analysis, and digital tools which allow for more precise variable rate applications. Additionally, new technologies like biologicals, fertilizer enhancers, and nutrient sources like Polysulphate promote greater ROI from nutrients that are already in a grower’s plan. Reducing input costs by reducing fertilizer inputs is not always possible or desirable, and there are many tools available to maximize the return for every fertilizer dollar spent. 

Since optimization is key to profitability, how do multi-nutrient products help growers? 

Let’s use Polysulphate as an example. By removing yield limitations that may exist due to sulfur deficiency, profitability is increased through extra yield or by indirectly affecting relationships like nitrogen use efficiency. Additionally, because Polysulphate contains four nutrients, all in the same granule, agronomists and growers can consider options to reduce or eliminate other common fertilizer sources like ammonium sulfate, potassium sulfate, or gypsum. 

Sustainable crop nutrition is top of mind, how can nutrient stewardship also optimize yields and profitability? 

Crop nutrition is one of the foundations of our modern society. A growing world population, which requires a dependable source of safe and nutritious food, will increase the agricultural industry’s need to focus on methods that ensure crop productivity, while also addressing the long-term sustainability of the world’s mineral-based nutrient reserves or stewarding nutrients like nitrogen and phosphorus that impact water quality. Optimizing yield and input cost per unit of crop output with our current crop nutrition decisions is a critical part of ensuring the long-term sustainability of food and agriculture. 

Are sustainability and innovation more than trendy buzzwords? 

We hear the terms sustainability and innovation thrown around a lot, but the fact is that innovation and sustainability are the cornerstones for survival and growth in a world where we are challenged to do more with less. Innovation without sustainability can sometimes lead to exploitation, so we need them both to generate long-term financial, environmental and social success. I think that is why ICL is such an exciting company to work for. They invested $53M in R&D this year in food tech, new-generation fertilizers, e-mobility, and other innovative areas of digital agriculture. They are committed to finding new solutions to both local and global food challenges. In 2021, ICL was recognized for their work in climate change, ESG practices, gender equality in the workforce, and fertilizer innovation. Agriculture is always exciting, but we are facing some of the greatest challenges we have ever faced as a community and it feels good to be part of something that can change the world for the better.