Corn prices soared nearly 4%, with soybeans jumping 2% as data showing that the wet US spring prevented growers planting on more than 8m acres compounded concerns over current Midwest dryness.
Corn for December closed at $4.72 ¼ a bushel in Chicago, a gain of 3.7% - and taking above 6% the contract's recovery from a low on Tuesday which represented the contract's weakest in nearly three years.
The rebound was fuelled by data from the Farm Service Agency, which is in charge of US agricultural support programmes, showing that 3.4m acres earmarked for corn were not sown, thanks to dismal spring planting conditions.
Richard Feltes at RJ O'Brien said: "At face value, today's FSA update suggests that corn, wheat and soybean acres may come down" from US Department of Agriculture estimates released in Monday's monthly Wasde crop report.
"I hear some calls that USDA's August acres may be overstated by 1.0m in corn and 500,000 in soybeans."
In Iowa alone - the top corn-producing state which recorded its wettest spring on records going back 141 years – farmers were unable to sow 613,000 acres which they had intended to plant with corn, and 106,000 acres which had been allocated to soybeans.
'Few opportunities for rain'
The figure supercharged headway which had already been made on concerns over a dearth of moisture in the Midwest – ironically, including Iowa, now the centre of dryness concerns, including a caution from USDA officials over the particular threat to soybeans.
"The trade in the row crop was already well supported when FSA data came out," Benson Quinn Commodities said.
"Current weather forecasts offer few opportunities for rain in the western Corn Belt and warmer temperatures.
"The corn and soybeans could use warmer temperatures, but some areas will continue to show stress without much needed moisture."
'Most supportive factor'
CHS Hedging said: "Dry and hot weather is pushing grains higher today. Weather forecasts show threats to crop development over the next 10-15 days."
And at Country Futures, Darrell Holaday said: "The most supportive factor is the lack of rain in the forecast. Temperatures will warm next week, but the models are not suggesting significant rain."
As an extra fillip to prices, weekly US export sales beat forecasts too, hitting 836,100 tonnes for new crop, ahead of expectations, including 309,000 tonnes bought by drought-affected Mexico.
Furthermore, technically, the rise took December corn above its 20-day moving average for the first time for getting on for two months, which it managed to close above too – for the first time since June 21.
That was an extra spur for hedge funds to close some of their hefty net short positions in corn, which were a record as of last week, and have indeed been profitable bets for the most of the last year.
'Brisk pace of exports'
Soybeans felt much the same kickers too, with dryness striking just as the oilseed is amidst its sensitive pod-setting phase.
(It was late-August rains last year which saved the crop from a harvest nearly as badly as corn's, after drought for most of the summer.)
Sure, the FSA number for prevent soybean plantings was not so large, at 1.6m acres.
But soybean export sales were uber-strong, at nearly 1.9m tonnes for 2013-14 delivery, making it the best new crop (ie buying ahead of the marketing year) week since February last year.
"Analysts were only expecting 1m tonnes at the high end of guesses," one broker said.
Richard Feltes said: "The brisk pace of new crop soybean export sales does not suggest world soy buyers getting more comfortable about Brazilian logistics," whose hold-ups have forced patience on importers.
Soybeans vs corn
The November soybean contract had its technical merits too, reclaiming its 50-, 75- and 100-day moving averages on Thursday, and getting not far off the 200-day line too.
However, one factor limiting its rise was its relatively high ratio with December corn already, which expanded to 2.75: 1 earlier this week, well above typical levels of 2.4: 1.
"The ratio had reached a point that if soybeans moved higher it would pull corn with it," one broker said.
"That is exactly what has happened as the ratio has dropped below 2.70: 1. Of course, the corn was so oversold that is was not hard to prompt some buying in that market, and it has occurred."
November soybeans closed up 2.1% at $12.65 ½ a bushel, reducing the ratio versus corn to 2.68: 1.
For the record, November soybeans have not risen more than $1 a bushel, or nearly 9%, from its 14-month low reached on Wednesday last week.
Also for the record, monthly US soybean crush data came in at 116.4m bushels, bang on expectations.
"How much more neutral a number can you get?" Jerry Gidel at Chicago-based broker Rice Dairy told Agrimoney.com.
Wheat was unlikely to lose, with the row crops gaining so strongly, and at a time when the poor performance in corn has represented a chain preventing gains on the back of decent demand signs.
But wheat's gains were limited, and by a succession of factors.
OK, prevent planting data on wheat were quite large, at 1.7m acres, although this was not entirely unexpected, given particularly wet conditions in the cop's heartland of North Dakota.
But weekly export data were a little underwhelming, at 490,000 tonnes, the lowest figure in two months.
And hopes for further sales took a dent from a further upgrade by Strategie Grains to its estimate for the wheat crop in the European Union, which has shown its export muscle by shipping 694,000 tonnes of the grain this week, the best figure of 2013.
Meanwhile, SovEcon cautioned the many investors itching to downgrade forecast for Russia's wheat crop, saying that a strong Siberian harvest – which, given the good condition of crops in neighbouring Kazakhstan, could well be on the cards – could yet force upgrades.
Wheat for September added 1.1% to $6.37 ½ a bushel in Chicago, still short of any of its major moving averages.
In Paris, milling wheat for November did better, up 2.1% at E185.75 a tonne, continuing to gain support from the EU export figure.
Among soft commodities, New York cotton managed gains, adding 0.3% to 91.79 cents a pound for December delivery, the contract's highest close in 17 months.
US exporters made an underwhelming entrance to the new cotton marketing season, recording sales of just 38,500 running bales for the first week.
But the fibre is gaining support nonetheless on forecasts of further rains for South East US cotton growing areas where crop quality is already being eroded by excess moisture.
"Over the next five days, all the significant rain will be over the Delta and the Gulf coast area," WxRisk.com said.
The tropical disturbance, ie potentially a nascent tropical storm, known as 92L threatens even worse if it makes landfall in the north east Gulf of Mexico as some suggest.
That would "enhance the rains over the south eastern states next week and cause severe and possibly catastrophic flooding for some locations" in the likes of Georgia and South Carolina, the weather service said.
But many other soft commodities struggled, especially those in which Brazil is a major player, as the real weakened again, recording a rate of R$2.35 to $1 for the first time since March 2009.
Arabica coffee for September eased 0.6% to 121.85 cents a pound, while raw sugar for October dropped 0.3% to 17.19 cents a pound, its first decline in seven sessions.