Deere & Co questioned forecasts of a jump in US corn sowings this year, predicting that soybeans would do a better job of holding their place in the annual spring battle for acres.

The maker of John Deere tractors concurred with outline US Department of Agriculture forecasts that plantings of America's four main crops – corn, cotton, soybeans and wheat – will rise 500,000 acres to 236.5m acres this year.

"Driven by strong global demand and low carryover stocks, our base case calls for an increase in total planted acres this year," Susan Karlix, Deere's manager, investor communications, said.

But the group limited the year-on-year rise in US corn plantings to 1.1m acres, taking sowings to 93.0m acres, the highest for four years but well below forecasts from many other forecasts.

94m acres, or more 

The USDA on Monday pegged sowings at 94.0m acres, the highest since 1944, a figure itself considered conservative by many investors.

At Benson Quinn Commodities, Jon Michalscheck said that while the USDA estimate was for "only" 94m acres, Monday's forecasts represented "a starting point".

However, Deere's numbers, while mirroring the USDA on what Ms Karlix called "a shift from cotton", failed to show the same shift from soybeans.

Indeed, area seeded with the oilseed was shown rising too, by 500,000 acres to 75.5m acres.

Battle for acres

Deere's stance tallies with a caution from the University of Illinois over expectations of a substantial switch from corn to soybeans, noting the relative firmness of Chicago's new crop November soybean lot over the December corn contract.

Farmers considering breaking with best agronomic practice by planting successive corn crops may be especially easily swayed to reverse these plans.

"The recent change in the relationship between new crop corn and soybean prices has reduced the potential profit advantage of a corn-after-corn rotation over a soybean-after-corn rotation," University of Illinois farm economist Darrel Good said.

"Average yields and projected costs still favour corn in those areas where corn-after-corn is common, but the margin has narrowed substantially since the first of the year and is still narrowing."

'Dangerous assumptions' 

Deere also factored in a lower corn yield than the USDA, of 162.2 bushels per acre. Monday's USDA forecast was of 164.0 bushels per acre.

Mr Michalscheck termed the USDA figure "somewhat optimistic".

And, at Australia & New Zealand Bank, Paul Deane forecast a yield of 154 bushels per acre, expanding on comments on Tuesday that the USDA had been unduly upbeat.

"US corn producers have only achieved an average yield of 160 bushels an acre or better twice in the last decade," he said.

And it was "dangerous" to make assumptions on extrapolating from past corn yields, given that they may have received a one-off boost in recent years from the adoption of genetically modified seed.

"The initial rapid adoption of GM corn has now run its course," Mr Deane said.