Crops had a bit of a struggle maintaining momentum on Wednesday, with the dollar turning from tailwind to headwind.
The dollar gained 0.2% against major currencies amid a feeling it had been oversold. The rebound made US exports, such as farm commodities, more expensive.
But they managed it in the end, helped by mounting expectation of a hard frost in key US growing regions.
"Very cold temperatures are predicted this coming weekend, probably ending the growing season in much of the northern half of the Midwest," Vic Lespinasse, marketwatcher for GrainAnalyst.com, said.
"This could do significant damage to the corn crop."
There is also a growing feeling that the bears have had their say in grain prices, with harvest pressure out of the way for wheat at least.
UBS, the investment bank, said that looks "increasingly likely" that crop markets have bottomed out, and dangled out the prospect of an "igniting" corn market if China does restart imports, as some analysts believe.
Moscow's Sovecon also raised hopes that Russia's bear market in wheat had run its course.
Technical factors also came into play, with Agritel, the Paris-based consultancy, noting that Tuesday's rally broke through several resistance levels on charts, notably $3.50 a bushel for Chicago corn.
That leaves crops more open to gaining from "the trend is your friend" investing.
Wheat for December closed up 2.75 cents at $4.63 a bushel, with December corn adding 1.5 cents to $3.59 ¾ a bushel.
Soybeans had an extra headwind to deal with – the prospect of a huge Brazilian crop.
Conab, Brazil's farm department, pegged the country's upcoming soybean crop at 62.3m-63.3m tonnes, up from 57.1m tonnes last year.
Strong Chicago prices, fostered by strong Chinese imports and the sidelining of Argentina from the export market by drought, have encouraged South American farmers to focus on soybeans for 2009-10.
That is somewhat to the detriment of corn plantings. Brazil is expected to product 50.9m-52.2m tonnes in 2009-10, around last year's 51m, Conab said.
Wheat sowings have fallen particularly low. Conab pegged Brazil's wheat harvest at 5.25m tonnes, down from a September estimate of 5.85m tonnes and 6.0m tonnes in 2008-09.
Chicago soybeans ended 2 cents higher at $9.11 ¾ a bushel.In Europe, Paris wheat for November ended up E0.25 at E125.50 a tonne, failing to hold ground above a resistance level of E126.00 a tonne.