Market expectations that US farmers have planted far more soybeans than they originally intended may be wrong, a broker has said, warning that talk of a big switch from corn may have been overhyped.

Alaron Trading, the Chicago-based broker, has bucked the consensus among its rivals that Tuesday's updated US Department of Agriculture estimates on farm plantings will show a sharp rise in soybean acreages.

Brokers surveyed by Reuters, the news agency, on average expect the USDA to raise its soybean plantings estimate by 2.1m acres to a record 78.1m acres - with analysts at Farm Futures forecasting a 79.6m-acre figure.

'Not likely'

However, Alaron has forecast that the USDA will trim its estimate by 675,000 acres to 75.3m acres, noting that talk that farmers have switched out of corn wholesale to take advantage of robust soybean prices looked misplaced.

"This would mean tossing out expensive corn seed and fertilizers and repurchasing bean supplies. Not likely," Alaron said.

And although corn planting had been dogged by rain delays, soybean sowing had to, with official data showing that 9% of designated US beans acreages remained to be planted on June 21.

Given that the cut-off date for statistics in Tuesday's report was June 20, "it makes sense" for the briefing to show a drop in soybean acreages, Alaron said.

This forecast may be adjusted upwards in July and August "if remaining acres end up planted".

Corn acreages to slip?

The broker forecast USDA will revise corn plantings to 84.2m acres, marginally higher than the 84.0m-acres consensus.

The department in March forecast corn plantings at 85.0m acres.