* Exporters struggle to source soy, corn for Oct. loadings
* Basis values could spike if rains persist
* Some exporters to renegotiate terms, pay demurrage
By Karl Plume
CHICAGO, Oct 9 (Reuters) - U.S. grain exporters are scrambling for corn and soybean supplies to meet their massive export sales commitments as persistent rains kept most farmers from harvesting their crops, trade sources said on Friday.
Exporters' basis bids are already at exceptionally strong levels and could strengthen further if rains continued to delay the harvest of a record soy crop and second-biggest corn crop.
Late spring planting followed by cool summer that slowed crop development and on-and-off autumn rains have exporters anxiously awaiting for an influx of corn and soybeans that, in a normal harvest year, would have hit export channels.
"It's going to be a tight and uncomfortable period for exporters and, until we get the harvest flowing more freely, they'll be scrambling," said Jay O'Neil, senior agricultural economist at Kansas State University's international grains program.
"We've seen the market act strong, act anxious for those bushels, but we haven't seen a real war take place yet for those bushels," he said.
Exporters at the U.S. Gulf, the main export point for U.S. agricultural goods, have a good supply of old-crop corn on hand, but basis levels have been firm as much of that corn may not meet export standards and needs to be blended with better quality new-crop supplies.
The spot soybean basis has been exceptionally strong due to a record export pace and the tightest supplies in 32 years at the end of the 2008/09 marketing year on Aug. 31.
On Friday, spot basis bids for corn shipped by barge to U.S. Gulf export elevators were around 60 cents a bushel over Chicago Board of Trade December futures contract CZ9, compared with about 55 cents over a year ago.
Spot soybean basis bids were 90 cents a bushel over CBOT November futures SX9, up from about 60 cents a year ago.
EYE ON HARVEST WEATHER
Traders said basis values for both commodities will remain firm as long as Midwest farmers are unable to forge ahead with their harvest the new crop.
Forecasters on Friday said that the U.S. Midwest could see scattered showers at times next week, but conditions would generally be drier than this week. However, fields may be slow to dry out due to colder temperatures. [ID:nN0966072]
"If we get some of that rain next week like the forecasts are calling for, it could get critical," said one Midwest soybean dealer.
Only 10 percent of the U.S. corn crop and 15 percent of the soybean crop were harvested as of last Sunday, well behind their five-year averages of 25 percent and 36 percent, according to the U.S. Agriculture Department.
If poor weather holds back the main thrust of the harvest for much longer, basis values, particularly for soybeans, could surge as exporters seek supplies to fill ocean-going vessels scheduled for loading later this month.
Exporters may be forced to renegotiate terms with their buyers if needed supplies are delayed. Stalled loadings of ocean-going vessels may be subject to demurrage fees, which can exceed $30,000 or more per day.
Soybean exports in the current marketing year are expected to reach a record 35.52 million tonnes, according to USDA. To date, U.S. export sales to China, the world's top soybean importer, are more than 220 percent ahead of a year ago. (Reporting by Karl Plume; Editing by Marguerita Choy)