MU study shows shows long-term drop in sulfur levels in soil

COLUMBIA, Mo. – Research at University of Missouri’s Sanborn Field in Columbia shows that sulfur levels in agricultural soils have fallen steadily since the 1880s.

A study led by MU Extension state soil science specialist Gurbir Singh points to sulfur deficiency in Missouri cropland, a finding that calls for precision application technology, more emphasis on crop rotation and better nutrient management choices to maintain crop yield and quality.

Other researchers on the project include graduate research assistant Rajinder Kaur, researcher Harpeet Kaur, agronomy professor Kelly Nelson, agronomist Gurpreet Kaur, MU Soil and Plant Testing Laboratory director Rasel Parvev and MU Agricultural Experiment Station director Tim Reinbott.

Researchers analyzed soil samples collected at Sanborn Field from 1888 through 2020. The study found that average sulfur levels dropped from 807 pounds per acre in 1888 to 232 pounds per acre in 2020 for the whole soil profile (0-48 inches).

Singh says the decline is likely linked to several factors, including reduced sulfur deposits from the atmosphere following clean-air regulations, sulfur removal by crops during harvest, movement of sulfur deeper into the soil profile and the widespread use of fertilizers that contain little or no sulfur.

Researchers also found that cropping systems and fertility practices greatly affected how much sulfur remained in the soil.

Rotations that included corn, wheat and red clover and received manure retained substantially more sulfur than continuous cropping systems.

In 2020, the corn-wheat-red clover rotation with manure and nitrogen had the highest sulfur levels, retaining about 75% of its original sulfur content. Some continuous wheat systems retained less than 10% of their original sulfur.

The findings suggest that growers can no longer rely on atmospheric sulfur deposits to meet crop needs. Instead, sulfur management has become a planned part of fertility programs. Researchers recommend regular soil and plant tissue testing, accounting for sulfur removed in harvested crops and considering sulfur-containing fertilizers or manure when needed.

While the study includes a long-term projection showing sulfur levels could continue to decline if current trends persist, researchers note that future sulfur availability will depend on factors such as weather, crop management, soil conditions and fertilizer practices.

Key takeaways

• Sulfur is becoming a more important crop nutrient than it was in the past.
• Average sulfur levels at Sanborn Field declined by more than 70% between 1888 and 2020.
• Crop rotation and manure applications helped maintain higher sulfur levels in the soil.
• Continuous cropping systems generally saw greater sulfur depletion.
• Soil and tissue testing are important for determining sulfur needs.
• Growers may need to include sulfur-containing fertilizers in nutrient management plans.

More information

Sulfur history and future: Lessons from the 132 years of Sanborn Field is available for free download.

About Sanborn Field

Sanborn Field is the oldest, continuous experimental field west of the Mississippi River and the third oldest in the world. It was established in late 1888 by J.W. Sanborn, who was looking to demonstrate the value of crop rotations and manure in grain crop production. Chemical fertilizer treatments were added by the early 1900s. Many of the 38 plots have the same crop rotation today as they did in 1888. Sanborn Field is unique because of its many long-term treatments on the same soil type.