Several agricultural studies over the past 20 years have confirmed what farmers are discovering in the field; less sulfur exists in today’s farming fields. The Clean Air Act is the interesting cause of this sulfur decrease. In turn, the demand for sulfur liquid fertilizers and API 650 liquid fertilizer tanks to store the products is on the rise.

The Clean Air Act was enacted in 1970 and amendments passed in 1990. The aim of this legislation was to significantly reduce six particular air pollutants, including the sulfur dioxide emissions from coal burning facilities. High levels of sulfur dioxide in the air cause haze and acid rain. This air pollution also increases respiratory health issues. People with asthma are particularly sensitive to higher levels of sulfur dioxide in the air.

The Clean Air Act and its Amendments have successfully reduced the atmospheric sulfur dioxide levels by 25% since its enactment. The graph below depicts the amount of sulfur dioxide emissions in each state in five year increments. The Midwest and south eastern states produced the most sulfur dioxide in the 1990s, and thus, experienced the most significant decrease in emissions based on the Clean Air Act requirements.

Lower sulfur dioxide emissions resulted in less acid rain, which for air quality is a good thing. However, that acid rain supplied the ground with sulfur that was used year in and year out by the crops planted and harvested in those areas. Farmers are now needing to use sulfur based fertilizers to restore the needed levels.

In line with the Midwest and south eastern states having the largest drops in sulfur dioxide emissions, increased demand for sulfur fertilizer has been progressing eastward over the past couple of decades. Below are graphs provided by Kugler Company. These graphs show the levels of sulfur in the ground in the 1990s compared to the 2000s. Again, corresponding with the decrease of sulfur emissions, the Midwest experienced the largest decrease in ground sulfur content.


On the macro level in the fertilizer business, the demand for sulfur based liquid fertilizers has increased and will likely continue upward. Ron Soden from Kugler Company says that they have seen demand for sulfur fertilizer continually increase and have a higher demand in the Midwest over the past decade. With the continued decrease in sulfur dioxide emissions, he says he expects the trend of higher sulfur fertilizer demand to continue.

At Heartland Tank Companies, we are seeing the sulfur shortage impact from the Clean Air Act as well. Ammonium thiosulfate is a common liquid fertilizer for supplementing sulfur. We have seen an increased demand for above ground storage tanks to store ammonium thiosulfate. This fertilizer is a common choice of farmers because it supplies both the needed sulfur and nitrogen to crops. Because of the product’s sensitivity to cold temperatures, we have also seen an increased demand for heated, insulated tank systems to prevent salting out. Using a heated, insulated system is especially recommended for year-round storage anywhere north of the I-70 corridor.

How do we know that this increased demand for sulfur products will continue? Several agricultural studies have evaluated the decrease of sulfur in the ground over the past 20 years. Every study confirms that we are just now seeing the beginning effects of decreased soil sulfur levels based on the effects of the Clean Air Act. Two major studies have been conducted by the extension programs of Michigan State University and the University of Illinois.

The Michigan State University Extension, conducted by forage educator Phil Kaatz, analyzed alfalfa throughout Michigan to observe the levels of sulfur. Kaatz chose alfalfa as his subject because the plant requires a lot of sulfur – “5-6 pounds per dry matter ton.” Healthy alfalfa plants and high yields are dependent on high levels of sulfur.

Part of the results of the Michigan State alfalfa study is that currently sulfur deficiency is a common occurrence when no sulfur based fertilizers are applied. This deficiency results in lower yields, stunted plant growth, and yellowing plants. Kaatz traces this soil sulfur deficiency back to the Clean Air Act in its success in lowering atmospheric sulfur dioxide that would deposit sulfur in the soil.

The main sources that deposit sulfur in the ground are fossil fuel combustion returning to the ground as acid rain, volcano eruptions, and ground water that has contacted coal or pyrite seams. In farming, sulfur is extracted from the ground by plants through absorption as sulfate. With the drastic decrease in ground sulfur and in result lower plant yields, the culprit has to be the decreased sulfur dioxide emissions from fossil fuel combustion, the aim of the Clean Air Act.

The type of soil and structure of the fields matters as to the depletion of sulfur. A twenty-year study was conducted by the University of Illinois Extension and found that fields with poorer soils and those with tile drainage systems experience the shortage of sulfur sooner.

The University of Illinois Extension study tracked the sulfur level of various farm fields, including those using tile drainage systems. One revelation was that even after applying bed ash to a field, initially providing a high concentration of sulfur, most of the sulfur had washed through the system in just three years. Thus, fields using tile drainage systems will likely need a steady application of a sulfur fertilizer to maintain good sulfur levels. This leaching was previously counter balanced by the atmospheric sulfur deposits by burning coal without restrictions on the sulfur dioxide air emissions.

So we expect to see more farmers needing to use sulfur liquid fertilizers. If you have customers in the Midwest and other regions that had a significant decrease in industrial sulfur dioxide emissions, you can recommend that they have their fields tested for sulfur levels if they experience a yellowing of plants or a dip in yields.

As your needs to store more sulfur liquid fertilizer increases, contact Heartland Tank Companies for assistance in strategically planning new liquid fertilizer tanks to keep up with the sulfur demand today and in the future.