By Carl Zulauf
Fertilizer price increases associated with the conflict in Iran seem likely to result in higher fertility costs for farmers for the 2027 crop year. Much attention has been given to higher nitrogen fertilizer prices. Prices for phosphate fertilizers, such as Diammonium Phosphate (DAP), have also been increasing. Today’s article links the increases in phosphate fertilizer prices to the significant increase in the price of sulfur, a primary input to the production of phosphate fertilizer products.
Phosphate Fertilizers
DAP and monoammonium phosphate (MAP) are two of the most common fertilizer products used by farmers to provide phosphorous nutrient to their crops. DAP contains 18% nitrogen and 46% phosphorous. MAP’s typical nutrient content is 11% nitrogen and 52% phosphorous. Thus, both products also contribute to nitrogen needs.
The production of DAP and MAP combines mined phosphate rock with sulfuric acid to produce phosphoric acid. The phosphoric acid is then combined with ammonia to produce a slurry which is then typically dried and granulated into the dry forms of MAP and DAP commonly used by farmers. Relative input requirements to produce DAP are 1.5 to 2 tons of phosphate rock with 0.4 tons of sulfur and 0.2 tons of ammonia. Changes in the prices of these primary inputs will translate to changes in the cost to produce phosphate fertilizers.
The primary source of sulfur is as a byproduct during the production of oil and natural gas, with a smaller portion of global production coming directly, or as a byproduct, from mining. China is the leading global producer of sulfur, accounting for nearly 23% of global supplies (USGS, 2026b). The U.S. is the second largest producer, accounting for close to 10%. Other major producers include Russia (8.9%), Saudi Arabia (8.6%), the United Arab Emirates (7.5%), Canada (6%), and Kazakhstan (5.7%).
The U.S. net import reliance on sulfur and sulfuric acid stood at 14% in 2024 and 2025 (USGS, 2026b), similar to net reliance on phosphate rock imports (see farmdoc daily from July 29, 2025 and USGS, 2026a).
DAP and Sulfur Prices
Figure 1 shows average DAP and anhydrous ammonia prices for the Corn Belt region of the US and Vancouver spot prices for sulfur since January 2024. Sulfur prices increased from less than $100 per ton in 2024 to more than $200 per ton by the spring of 2025. Sulfur prices surpassed $400 per ton at the end of 2025 and have in recent months exceeded $1,000 per ton. The sharp increase since March of 2026 is attributed to logistical disruptions in the Middle East region due to the conflict in Iran. The disruptions are also leading to export restrictions being put in place by major producers, such as China and Russia, to address domestic supply concerns putting further pressure on global supplies and contributing to higher prices and the potential for continued volatility moving forward.
Source : illinois.edu