Last days of the month, and quarter, are often viewed as bringing a negative feel to agricultural commodity markets, as funds tidy up positions and withdraw cash for paying clients and bonuses.
This month-end had an extra negative twist, in Washington's failure to agree a budget deal, leaving a US government shutdown looking increasingly likely.
Furthermore, there was some downbeat news on the world's second-largest economy too.
A purchasing managers' index for the Chinese economy published by HSBC was, at 50.2, 0.1 points higher this month than in August, but well below the preliminary survey result of 51.2 that was announced just last week.
The upshot was a negative start to many markets, with shares tumbling 2.1% in Tokyo and 1.3% in Hong Kong, if adding 0.7% in Shanghai.
In Europe, shares dropped 0.9% in London and 1.1% in Frankfurt. They are expected to open a little lower on Wall Street too.
Among commodities, copper fell, if not anywhere near enough to jeopardise gains of 8% this quarter, the biggest quarterly gain since the first three months of 2012.
Brent crude shed 0.8% to drop below $108 a barrel.
'Broken out of its downtrend'
And agricultural commodities came under selling pressure too, even bulls' recent favourite – wheat.
Technically, the grain has transformed in investors' eyes to a far more bullish aspect, with Chicago's December contract pulling last week back over 50-day, 75-day and 100-day moving averages, the last of which for the first time in 2013.
Furthermore, from the contract's weekly chart, "you can clearly see where wheat has broken out of its downtrend", dating back to November, a US broker said, after the grain managed five successive positive closes last week.
"If the short-covering continues the next major target would be in the low $7.40s a bushel, right at the 38.2% retracement level," a key point for followers of Fibonacci analysis.
'A bigger feature'
However, while any position closing encouraged by month-end could look price supportive, given that hedge funds have a sizeable net short in Chicago wheat futures and options, of 35,000 lots, with short positions requiring buying to close, it is not quite so straightforward.
There are now enough investors who have bought long positions earlier in the month, as wheat begin its recovery of nearly $0.50 a bushel from a September 5 low, to mean that profit-taking on long holdings has become "a bigger feature", Benson Quinn Commodities said.
"Given the impressive value gained last week, who could argue with the speculative community about taking some profits off the table," the broker said.
Especially when there is a key report later, the US Department of Agriculture's quarterly report on domestic crop stocks, as of September 1, for which wheat is seen as taking the headline role.
It is "conceivable" that wheat stocks could come in below the forecast of 1.913bn bushels, as "many believe more wheat was fed in the last quarter than the USDA has accounted for", the broker said.
As an extra negative for wheat futures, the benchmark January contract eased on China's Zhengzhou exchange, by 0.1% to 2,849 yuan a tonne, with prices there being closely watched given China's return to buying imports en masse, following a rain-compromised domestic harvest.
In another country, Brazil, where import demand is being raised, for similar reasons, "the agriculture minister now believes that Argentina will have enough wheat to supply Brazil come harvest," CHS Hedging said, terming this "negative demand news for US wheat".
And while Ukraine is severely struggling with sowing its winter grains, mainly wheat, a positive for prices, that is being offset by what the broker terms, in the US "the best winter wheat seeding conditions we've seen in the last few years".
Wheat for December eased 0.8% to $6.80 ¾ a bushel in Chicago as of 09:40 UK time (03:40 Chicago time).
With wheat falling, it was hard for fellow grain corn to make ground either, given the pressure prices are under from a US harvest which is turning out better than expected, according to yield reports.
"Analysts continue to up their estimated national corn yield as positive yield reports flow in from the countryside," CHS Hedging said.
That said, the US corn harvest is still in its infancy, with USDA data later expected to show it 14-15% complete.
And, as in a sense a positive for prices, hedge funds have raised their net short in Chicago corn futures and options to a record high of more than 126,000 contracts, with extreme positioning often provoking doubts as to the appetite to take the trend further.
Corn for December rose, if only by 0.1% to $4.54 ½ a bushel.
'Bigger yield and better production'
Soybeans, however, found headway more difficult, dropping 0.4% to $13.15 a bushel for November delivery.
The oilseed is coming under pressure from the US harvest too, albeit one which is producing less promising results than for corn, if hardly the disastrous ones some investors had feared.
"The market feels like it is trading a bigger yield and better production" than the USDA has forecast," Benson Quinn Commodities said.
Furthermore, with a Chinese holiday in offing, "look for soybean export demand to be drastically reduced," CHS Hedging cautioned.
China is the top importer of the oilseed, and its purchases are closely watched.
Elsewhere in the oilseeds complex, palm oil did better, adding 0.2% to 2,314 ringgit a tonne, helped by a forecast that output from Indonesia, the top-ranked producer and exporter, will come in short of previous forecasts.
Derom Bangun, chairman of the Indonesian Palm Oil Board, forecast that output will hit 26.7m-27m tonnes, above last year's 25.5m tonnes but below a previous forecast of 28m tonnes.
The downgrade reflected "the wet weather in the last dry season disturbing pollination", Mr Bangun said.
The revision offset some disappointment at Malaysian palm exports, which Intertek showed rising 2.1% this month, a gain, but well below the pace seen earlier in the month.
Among soft commodities, robusta coffee recovered a little from a three-year low hit in the last session, adding 0.3% to $1,614 a tonne in London for November delivery.
But how long will the bounce last, given pressure from prospects of a strong harvest in Vietnam, the variety's top producer, starting next month?
"Going forward, the adding of new coffee supplies to current old-crop supplies will continue pressuring prices," Joyce Liu at Phillip Futures said.
Raw sugar for October added 0.5% to 16.96 cents a pound in New York, defying, on its expiry day, weakness elsewhere in the complex. With the March contact easing 0.1% to 17.72 cents a pound.
However, investors are braced for potential volatility, given talk of a huge delivery against the October contract,
"The delivery was pegged at potentially above 1m tonnes, larger than average, as Brazil entered its final phase of the crushing season," Ms Liu said.