Will livestock farmers, importers or ethanol plants blink first?
US farm officials are poised later on Friday, in their flagship Wasde crop report, to cut their forecast for domestic corn supplies to the lowest since the 1930s.
Analysts believe that, following last week's revelation by the US Department of Agriculture that domestic corn stocks were much lower in March than the market had expected, the official estimate for inventories when the 2010-11 crop year closes in August will be cut to 586m bushels.
That's tight. When compared with demand, this would imply a so-called stocks-to-use ratio, a key measure of supplies, of some 4.3%, falling below the 4.5% reached in 1937.
Even so, the estimate would assume significant rationing in the second half of the crop year.
America's corn inventories were 170m bushels short of forecasts in March. The USDA is expected to pass on only half that into its estimate for stocks at the end of 2010-11.
The trouble analysts are having is assessing which users will be the first to throw in their hand.
Livestock farmers might appear the obvious weak link, given that they can switch to alternative sources of feed, notably wheat. Indeed, broker Allendale earlier this week said, that on a protein-adjusted basis, feeding wheat was already cheaper than using corn in fodder.
Forecasts for Wasde estimates for US corn stocks, end 2010-11
Average of estimates: 586m bushels
Highest estimate: 650m bushels
Lowest estimate: 515m bushels
Current USDA estimate (March Wasde): 675m bushels
Stocks at close of 2009-10: 1.71bn bushels
Sources: USDA, Thomson Reuters
"We could see some use of soft red winter wheat," whose early summer harvest will come "as the US is getting low on corn supplies".
Even so, the figure of extra wheat use in feed, which is currently running at well under 200 bushels a year, might be, at best, 50m-150m bushels, a level which would "not have a huge impact on the corn balance sheet".
Furthermore, record cattle and hog prices have shielded livestock farmers from the higher grain prices, and indeed encouraged them to maximise animal weights to make the best of diminished herd numbers.
Substitution of corn with wheat was more likely abroad, in countries such as China, which might be more tempted to tap ample supplies of feed wheat from Australia and Canada rather than import expensive corn, Mr Bos said.
Forecasts for Wasde estimates for soybean, wheat stocks, end 2010-11
Soybeans: 137m bushels, -3m bushels on current USDA estimate. (End 2009-10 151m bushels)
Wheat: 857m bushels, +14m bushels on current USDA estimate. (End 2009-10 976m bushels)
Sources: USDA, Thomson Reuters
Shipments are, at nearly 12.6m tonnes, 20% higher than those at the same time in 2010, on Agrimoney.com calculations, and many believe more Chinese orders are on their way, despite the appeal of Aussie wheat.
Nor do ethanol plants, which consume approaching 40% of America's corn crop, look obviously ready to trim their demand yet.
Latest official data, for the week to April 1, showed output down, but, at 902,000 barrels a day, only by 1,000 barrels a day on the previous week, supported by higher gasoline prices.
"So far so good as far as margins are concerned," Tom Waterman at US-based Ethanol Monitor said.
"Ethanol prices are holding up largely due to the fact that gasoline prices are up. And we're exporting more."
One key to the issue of who cracks first may come down to the levels of corn that different user groups bought forward while prices were cheap.
"Many livestock producers have actively hedged their corn input costs, which means they have been insulated from the corn price increase to date," Mr Bos said.
US Commodities said: "Most ethanol plants have three-to-eight weeks of corn coverage."
"The key to this market is when ethanol production/demand slows," the broker added, reporting that some western US ethanol plants were already running at a loss, although some other analysts believe that sites can absorb significantly higher corn costs.
An alternative scenario was presented by Sid Love, at Kropf-Love Consulting, who said that demand may just make it through to lower stocks after all, taking them well below the end-year figure of 600m bushels that many consider the "pipeline" supply.
"The actual number could go as low as 400m bushels. But I don't think [the USDA] will want to throw fuel on the fire."
After all, that would imply a stocks-to-use figure of just under 3%, with obvious implications for raising prices.