Brazilian farm officials sided with commentators reducing expectations for Brazil's soybean crop as US attaches cautioned too over Argentina's harvest prospects.

Conab, the Brazilian crop bureau, cut by 1.3m tonnes, to 82.1m tonnes, its forecast for the domestic soybean harvest, if still meaning the crop is on track for a record high.

"The reason for the decrease is adverse weather conditions, such as excessive rain in the Midwest and drought in the south of the country," the bureau said.

However, conditions had not dented prospects for corn production, for which the forecasts was kept at 76.1m tonnes - including a 41.3m-tonne safrinha crop planted after the soybean harvest, and now seen outperforming the so-called main crop, viewed at 34.8m tonnes.

Spread of estimates

The revisions are the latest in a series by commentators on the Brazilian soybean crop, most of which have been negative, but with some analysts raising expectations.

These include Agroconsult, which earlier this week lifted its forecast by 200,000 tonnes to 84.2m tonnes, with Informa Economics on Friday upgrading its figure by 500,000 tonnes to 84.5m tonnes, making these groups among the most optimistic observers.

US Department of Agriculture attaches in Brasilia this week cut their forecast to 82.5m tonnes, 1.0m tonnes below the USDA's official estimate, while Celeres has proved among the most pessimistic forecasters, with a figure of 80.1m tonnes.

Nonetheless, this would represent a large crop – and it is Brazil's logistical hiccups, rather than the risk of crop disappointment, which is of more concern to investors.

'Rain came too late'

Separately, USDA staff in Buenos Aires cut their forecast for the Argentine soybean crop, to 50.0m tonnes - 3.0m tonnes below the department's official estimate – warning that the two-month hot and dry spell which broke last month had caused some "irreversible" damage, especially in the north of the country.

"For the early-planted soy in the southern Santa Fe, Cordoba and northern Buenos Aires province, the rain came too late," the USDA staff said.

"Pods were aborted during the driest part of the season and now they are already in the seed-filling stage.

"Contacts estimate that in this case, plants that would previously yield 4 kilogrammes per hectare are now expected to yield 2.5 kilogrammes per hectare, nearly a 40% drop."

The potential for frosts represented a threat of a further downgrade still.