Hopes for big South American crops buyers are relying on to fill supply gaps left by drought-hit US harvests took a knock with the first talk that a difficult sowing season had curtailed yield harvest.
The run of upgrades to Brazil's soybean crop went into reverse as Michael Cordonnier, the respected crop scout, trimmed his forecast to 80m tonnes, from 81m-83m tonnes, albeit still a record high.
He warned that a downgrade was on the way to his forecast for Argentine corn too, following persistent rains which have left "fields two-feet deep in water as far as the eye can see".
And, separately, Oil World cautioned that "there is now a higher risk that initial estimates of a sharp increase in [South American] soybean production… will not fully materialise".
The analysis group has pegged the continent's 2012-13 soybean output at 153.5m tonnes, a rise of 36m tonnes year on year.
The downgrades follow a further period of weather extremes, following last season's drought, which has landed much of Argentina and southern Brazil with excessive rain, while leaving many central and northern parts of Brazil with too little moisture.
"Excessive rainfall has reportedly been received on roughly 50% of the total Argentine oilseed and grain area," Oil World said.
Dr Cordonnier, noting that Argentine corn sowings were 38% complete, some 20 points behind last year, said that "planting is very troublesome", adding that the slow rate of seedins was "becoming a big issue".
"Argentina is not going to get a lot of corn planted any time soon,"
While this could boost production of soybeans, as farmers switch to a crop which can be later planted, it was not clear that farmers "will not have problems planting soybeans as well", he told Agrimoney.com.
'Very hot and very dry'
In Brazil, soybean sowings were also running behind, by as much as 20 points in Goias, where weather has been "very hot and very dry", with temperatures reaching 103 degrees Fahrenheit, Dr Cordonnier, at Soybean and Corn Advisor, said.
Oil World said that Brazil's soybean sowings were lagging by 1.3m-1.5m hectares, as of October 19, adding that it was likely that "in the first or second week of November there will be headlines circulating in newswires about alarming soybean planting delays of around 3m hectares behind last year's pace in Argentina and Brazil combined".
The problem for the central and northerly regions was that in some areas, such as the western part of top soybean-growing state Mato Grosso, the first rains arrived on schedule last month, prompting farmers to make a start on sowings.
"But they never got the second rains" needed to support the crop, Dr Cordonnier said.
Germination rates were, at 25-35%, poor, meaning many farmers were "waiting for rain, and will then replant".
Rains are in fact forecast for the next two days, which could have a significant influence.
"it's time to get the stuff in the ground. It has been a spotty start to the growing season."