MAP closed the week ending Oct. 2 at $978 per short ton and DAP at $945.56, according to USDA Agricultural Marketing Service distributor asking-price data — even as sulfur, the raw material whose price climbed from below $100 per ton in 2024 to more than $1,000 at points in 2026, began retreating across several regions.

The disconnect defines the current fertilizer market. DAP asking prices slipped 1.7% for the week and MAP traded below recent levels, while the international sulfur market softened enough to shift negotiating power toward buyers heading into fourth-quarter settlements, ICIS reported Oct. 2. QatarEnergy cut its October sulfur price by $45 per metric ton from September, and Tampa and European fourth-quarter contracts were expected to settle below third-quarter levels.

The open question is whether cheaper sulfur works through the phosphate supply chain before U.S. growers lock in fall purchases for the 2027 crop.

Why sulfur drives phosphate costs

Producing one ton of DAP requires roughly 1.5 to 2 tons of phosphate rock, 0.4 ton of sulfur and 0.2 ton of ammonia, according to research from the University of Illinois and Ohio State University. Mined phosphate rock is treated with sulfuric acid to produce phosphoric acid; ammonia is added before processing into finished MAP or DAP. That input structure turned the sulfur rally into a direct cost shock for one of agriculture's core nutrient chains.

The university researchers documented sulfur below $100 per ton during 2024, above $200 by spring 2025 and beyond $400 by the end of that year. Spot values exceeded $1,000 per ton during 2026. Their analysis found a 0.70 correlation between Corn Belt DAP prices and Vancouver sulfur prices since 2024; the DAP-anhydrous ammonia correlation ran at 0.65. Correlation is not causation, but the raw-material and finished-product markets have moved in near lockstep.

Supply geography compounds the exposure. China produces nearly 23% of the world's sulfur, the United States close to 10%, Russia 8.9%, Saudi Arabia 8.6%, the UAE 7.5%, Canada 6% and Kazakhstan 5.7%. Despite its oil and gas sector, U.S. net import reliance for sulfur and sulfuric acid ran about 14% in 2024 and 2025.

The October shift

Entering October, the sulfur rally met resistance from the industry that consumes it. ICIS reported in September that prices fell by roughly $40 to $150 per metric ton across several importing markets as phosphate producers cut operating rates or postponed purchases. High feedstock costs had squeezed manufacturing margins to the point where buying less sulfur beat running plants at uneconomic rates. Additional shipments from Kazakhstan added supply relief.

That dynamic creates a paradox for growers. Falling sulfur prices point toward lower phosphate manufacturing costs, but weaker sulfur demand can also signal that phosphate plants are producing less MAP and DAP. ICIS noted that reduced sulfur purchasing could ultimately limit phosphate output and cap how far finished fertilizer prices decline. Cheaper feedstock on one side; tighter finished-product supply on the other.

Tight inventories and logistical risks argue against assuming a rapid return to historically normal prices, even after the October softening.

Price transmission lag and the farm bill

The USDA-based figures are national averages of distributor asking prices, generally FOB — not final farm-gate costs. Freight, dealer margins and local supply conditions can push the actual bill higher. Fertilizer markets also rarely transmit raw-material declines immediately; inventories, contracts, freight and previously purchased feedstocks create lag before upstream savings reach the farmer.

The broader numbers frame the timing. Potash stands at $571.35 per ton (up 6.8% on the week) and anhydrous ammonia at $945 (up 15.9%). On a nutrient basis, current asking prices translate to roughly $0.94 per pound of P₂O₅ in MAP and $1.03 in DAP, before crediting nitrogen value.

Those economics land on a tightening farm budget. USDA's September forecast puts 2026 U.S. production expenses at $492.8 billion, up $21.2 billion, or 4.5%, from 2025. Fertilizer, lime and soil conditioner expenses are projected to rise $5.3 billion, or 15.3% — among the sharpest increases of any major cost category. Net farm income is projected at $158.4 billion, down 2.6% in nominal terms and 5.5% after inflation.

Agronomic constraints on cutting phosphorus

Potassium cannot replace phosphorus, and additional nitrogen cannot correct a phosphorus deficiency. Drawing down soil reserves for one season can buy financial flexibility; repeating that strategy across several crop cycles pushes soil-test values toward critical levels and raises agronomic risk. Growers and retailers are therefore leaning on soil testing, variable-rate application, nutrient removal calculations and field-by-field prioritization. Livestock manure offers an alternative phosphorus source where supplies and freight economics allow, and biological crop nutrition products are under evaluation — though the source notes they should be judged on replicated agronomic evidence and economic return rather than treated as automatic substitutes for phosphorus removal.

QatarEnergy's $45-per-ton October reduction and expectations of lower fourth-quarter settlements suggest the raw-material market may have passed its most extreme phase. Whether that correction reaches growers in time to materially lower 2027 fertility costs is now the question that matters most.