Monday made for difficult going for risk assets anyway.
Eurozone debt concerns revived with a failure by Greece to reach a deal with creditors to see of the risk of default, and with a European Union summit pushing the issue back up the agenda.
Meanwhile, China disappointed many investors by reopening after new year celebrations without easing monetary policy, as many had hoped, given a slowing economy and apparently retreating inflation threat.
"China returned from holiday with no new financial policy," Paul Georgy at broker Allendale noted.
And, as if that were not enough for crops to crops to cope with, the news flow for crop fundamentals turned negative too.
"There is no confirmation as yet, but it doesn't help sentiment wise given Friday's announcement that Indian export quota may be increased at a February 7 meeting," Mr Briggs said.
Raw sugar for March closed down 1.5% at 23.85 cents a pound in New York, while London white sugar for the same month eased 0.5% to $634.20 a tonne.
And, in Chicago,
"The market reacted savagely to weekend rains in Argentina," Mr Briggs said.
And the particular setback for soybeans is that, as a later crop than corn, is has more chance of recovery from late rains.
"February is a key reproductive month [for soybeans] and the forecast is pointing to increase rainfall and moderate temperatures," Darrell Holaday at Country Futures said.
At weather service World Weather, Drew Lerner said that "sufficient rain will fall over the coming week to further reduce Argentina crop stress.
"Crop conditions will likely improve with the soon-to-be-reproducing soybeans, late
This on top of US export data (by cargo inspections) which did not impress, neither for soybeans, at 41.5m bushels (up week on week but down year on year) nor corn, at 22.5m bushels (lower on both scores).
US Commodities said it was "concerned with the slow soybean export pace, trailing last year's values by 417m bushels.
"South America competition is now closing in."
Mr Holaday said: "We mentioned last week that we have a lot of concern about the slow US export pace in the last month and that is a big factor in the sell-off today."
March soybeans ended down 2.8% at $11.85 ¼ a bushel.
For corn, at least, Monday's poor export data did not dampen expectations that US shipments will beat current US Department of Agriculture estimates.
Nor has the grain the same recovery potential from Argentine rains, as mentioned above.
But another support for corn, strong US cash prices, also began to crack.
"Basis is losing steam quickly and macros look to consolidate lower," GrainAnalyst.com trader Mathew Pierce said, adding that this was "not a good sign for all those on the bull side".
Corn for March closed down 1.6% at $6.31 ¾ a bushel in Chicago, after a seven-day winning streak.
"Over the next five days the main driving feature for Europe and Western Russia as well as the Ukraine will be the huge, massive Arctic high pressure system," weather service WxRisk.com said.
"This feature will simply dominate the weather maps for the next week - at least. Temperatures will run much below normal, and at times super below normal."
And, on export news, while weekly US exports were hardly booming, at 18.7m bushels, South Korea provided a boost by buying, cheaper, feed wheat over the weekend in place of corn.
There was some potentially positive weather news for Minneapolis spring wheat, given the dearth of rain in northern US and into Canada, major growing areas.
"Strength due to drought expansion in northern [US] states is a positive impact on this market moving into planting," Mr Pierce said.
But Minneapolis wheat for March in the end closed down 0.9% at $8.19 a bushel, faring worse than Chicago wheat, which finished 0.4% lower at $6.44 ¾ a bushel.
Paris contracts did better, if only thanks to a weaker euro, with the March lot adding 0.1% to E209.00 a tonne.
London wheat for May fell 0.3% to £165.00 a tonne.