Conab ditched expectations of matching last season's record corn crop, after weather delays to plantings, but stood by expectations for a huge soybean harvest, encouraged by "remunerative prices".
The official Brazilian crop agency, which in outline forecasts last month had held out the potential for an 82.6m-tonne corn harvest, reduced to 79.6m tonnes its expectation for the biggest result that could be achieved.
The figure reflected a slower start to the first-crop sowing season, with in the south 30% of plantings completed in Parana and 50% in Rio Grande do Sul, "lower compared to last year due to heavy rains at the end September, which hindered planting", Conab said.
In Santa Catarina, "for the same reason, planting has not yet started", with planters idled "waiting for a reduction in soil moisture.
In the key central states, such as Mato Grosso, too little rain is the problem.
"Producers are awaiting rains to enable them to initiate the seeding," the bureau said, adding that the harvest could be limited to 78.4m tonnes - although this would still be more than the 72m tonnes that the US Department of Agriculture has factored in.
For soybeans, Conab forecast a harvest of 87.6m-89.7m tonnes, a little higher than the range of 84.7m-89.9m tonnes made in last month's initial projections.
The forecast reflects expectations of area increases of up to 5.9%, as Brazilian farmers "prioritise" soybeans, thanks in part to "remunerative prices".
Conab forecasts for Brazilian crop production, 2013-14
Corn: 78.4m-79.6m tonnes
Soybeans: 87.6m-89.7m tonnes
Wheat: 4.77m tonnes
Indeed, sowings are expected to rise potentially to a record 29.4m hectares, "consolidating a increasing trend in all regions".
Wheat import prospects
The bureau also trimmed its estimate for the Brazilian wheat crop by 180,000 tonnes to 4.77m tonnes, reflecting a July frost which cost more than half production in Parana.
On top of some incidence of fungal disease, "the biggest damage has been caused by low temperatures", Conab said.
Nonetheless, with extra area set to lift the crop 9% above last year's result, the bureau curtailed expectations of large growth in imports, in fact seeing them drop to 6.7m tonnes in the year to the end of July 2014, from 7.0m tonnes the year before.
However, this forecast assumes a drop of more than 1.0m tonnes to 600,000 tonnes in Brazilian exports of the grain.
The country's wheat import needs are being closely watched by markets given the weak supplies in Argentina, Brazil's default source for imports, with orders seen being switched to Canada, Europe and the US.
*Separately on Wednesday, Lanworth lowered its forecast for Brazilian corn production by 1.8m tonnes to 74.10m tonnes, cautioning that weak prices will lower farmers' enthusiasm for spending heavily on second-crop, or safrinha, corn sown early in the calendar year on land cleared by the soybean harvest.
"The declining corn price and difficulty marketing last season's record large crop could prevent farmers in these states from purchasing inputs required to plant and/or maintain a high yield second corn crop," the consultancy said.