Corn futures posted their largest August rally in more than 50 years, according to Zaner Ag Hedge's Ted Seifried, as damage to Black Sea ports, record speculative fund buying, and rising concerns over the Strait of Hormuz combined to lift grain markets through mid-September.

The rally builds on weeks of cascading events. A Ukrainian drone and missile strike hit the main grain conveyor at Russia's Novorossiysk port on August 12. Roughly 70% of Russia's export capacity now sits idle, industry reports indicate. Ukraine's grain exports have fallen 60% year-over-year, pushing wheat and feed-grain buyers toward U.S. sellers.

"We just saw the largest rally (in the corn market) in the month of August in over 50 years," Seifried said on Iowa Public Television's "Market to Market" program. For the most part, he added, the market has "now factored that in."

What do the latest USDA numbers show?

USDA's September supply-and-demand report trimmed the 2026 corn yield estimate to 180.7 bushels per acre, based on Farm Service Agency certified acreage. Higher harvested area offset the per-acre cut, keeping production essentially steady at 16 billion bushels.

Private analysts put the yield higher at 181 bushels, but they removed 2 million acres. That combination widens the expected gap between U.S. supply and demand to roughly 330 million bushels, according to analysts cited by Wisconsin Farmer.

Why are funds piling in now?

Andersons Grain analyst Jacob Christy said managed-money funds now hold a record net-long position in corn. Speculators across agriculture — corn, soybeans, wheat — hold an aggregate all-time-high long, he noted. The last four weeks alone mark the largest speculative buying spree in agricultural market history.

His colleague Joe Brown said the macro backdrop explains the flow. Stocks remain under pressure, bond markets have struggled, and investors want inflation hedges. "In an environment filled with geopolitical uncertainty and volatile headlines, commodities have become an attractive destination for capital, seeking both inflation-protection and exposure to global risk events," Brown said.

How badly has Black Sea trade been hit?

Russia ranks as the world's top wheat exporter, with Ukraine second or third. Ukrainian attacks on Russian grain terminals and shipping vessels now span the Black Sea and Sea of Azov; Russia has shifted loadings to Baltic ports. Some war-damaged facilities will need months or years of repair, Seifried said.

Three Ukrainian ports near Odesa that account for roughly 60% of Ukraine's $3.5 billion in monthly export revenue face a possible Russian blockade, the New York Times reported. Egypt, historically a Russian wheat buyer, has already signed alternative supply deals. "There are now some actual structural issues and that's what is creating drama in the wheat market," Seifried told "Market to Market."

Nearly 25% of the world's grain typically moves through Black Sea ports — a flow now largely halted.

Which other producers are running short?

France and China are forecasting lower corn yields after summer drought and heat. France ordinarily exports 40% of its corn crop to other EU members, a flow that will shrink sharply this year. That shortfall channels additional demand to U.S. exporters alongside tonnage Ukraine cannot move.

South America faces a separate squeeze: limited fertilizer for next year's crop. The wildcard above all, Seifried said, is whether China resumes large grain purchases.

Why does the Panama Canal matter?

A strengthening El Niño has cut rainfall 34% below the May-through-August average across the canal watershed, with inflows running 44% below normal. Gatun Lake, which feeds the lock system by gravity alone, has dropped low enough that authorities reduced maximum ship draft to 47.5 feet. Daily transits now sit near 34, split nine through one lock and 25 through the other, and slot suspensions continue.

NOAA put the odds at 90% for a "very strong" El Niño this fall and winter, with a 69% chance conditions hit historic-strength thresholds between October and December. Each ship transit uses about 26 million gallons of freshwater that's then lost to the ocean. Smaller cargo loads and longer waits lift delivered costs for grain and fertilizer.

The canal carries more than 3% of global ocean commerce, typically moving around 14,000 vessels a year. This marks only the second time the waterway has imposed transit restrictions; the first came in the 2023-2024 drought.

Strait of Hormuz disruption, canal bottlenecks, and Black Sea outages now stack on each other, pushing logistics costs higher and keeping basis volatile for U.S. farmers still selling old-crop corn ahead of harvest. Whether September's rally extends through harvest hinges on how long Ukrainian attacks keep Russian terminals offline — and on whether Chinese buyers re-enter the market.