CHICAGO, Sept 16 (Reuters) - Spot basis bids eased for corn at U.S. ethanol plants on Monday, while Iowa processing facilities raised corn and soy basis bids.

* U.S. farmers are starting to harvest massive corn and soy crops, but some facilities are not seeing much supply come in from the fields yet.

* Ethanol plants in Indiana and Illinois reduced their corn bids by 5 cents a bushel and 6 cents a bushel from Friday, respectively.

* A corn processor in Cedar Rapids, Iowa, raised its bid by 2 cents per bushel to 22 cents over Chicago Board of Trade December corn futures for delivery before Sept. 22, in a sign the location is willing to pay a hefty premium for immediate supplies. The processor posted bids of 10 cents under futures for the last half of September and 20 cents under for October, when harvest will be farther along.

* The U.S. Department of Agriculture is slated to release updates on corn and soy crop condition ratings and harvest progress after CBOT trading ends on Monday.

* Recent dry weather has raised some questions over yield potential.

* Ahead of harvests, the U.S. soybean crush dropped below all trade estimates in August to the lowest point for a single month in nearly three years, according to National Oilseed Processors Association data.

* CBOT December corn was down 3 at $4.10-1/4 per bushel by 12:35 p.m. CDT (1735 GMT), and November soybeans

were down 1-3/4 cents at $10.04-1/2 per bushel.

Basis values are quoted against CBOT futures in cts/bushel:

ELEVATORS

CORN SOYBEANS

CINCINNATI OH -51 + Z UNC -65 + X DN 6

BURNS HARBOR IN UNQ UNC UNQ UNC

DECATUR IN UNQ UNC

DES MOINES IA UNQ UNC

LINCOLN NE -20 + Z UNC

PROCESSORS

CORN SOYBEANS

DECATUR IL -18 + Z DN 3 -20 + X UNC

DECATUR IN -33 + X UNC

MORRISTOWN IN -35 + X UNC

LAFAYETTE IN -30 + X UNC

CEDAR RAPIDS IA +22 + Z UP 2 -40 + X UNC

COUNCIL BLUFFS IA -15 + X UP 10

LINCOLN NE -25 + X UNC

BLAIR NE +10 + Z UNC

RIVER TERMINALS

CORN SOYBEANS

TOLEDO OH -55 + Z UNC -70 + X UNC

SENECA IL -40 + Z UNC -40 + X UNC

SAVANNA IL -31 + Z UNC -56 + X UNC

DAVENPORT IA -25 + Z UNC -62 + X UNC

ETHANOL PLANTS

LINDEN IN -40 + Z DN 5

UNION CITY IN -47 + Z UNC

ANNAWAN IL -30 + Z DN 6

COUNCIL BLUFFS IA -18 + Z UNC

SRW WHEAT

TOLEDO OH -45 + Z UNC

CINCINNATI OH UNQ UNC

DECATUR IN -75 + Z NC

BURNS HARBOR IN UNQ UNC

NOTE: 0 = option price, UNC = Unchanged, UNQ = Unquoted

NC = Not comparable, DPI = Delayed Price, N/A = Not available,

F = January, H = March, K = May, N = July Q = August, U = September, X = November, Z = December

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LINKS:

For U.S. forward basis spreadsheets, please click:

- CBOT corn report

- CBOT soybean report

- CBOT wheat report

- U.S. grain barge freight values

- U.S. Midwest cash grain PM

- U.S. CIF/FOB Gulf Grain

(Reporting by Tom Polansek in Chicago; editing by Jonathan Oatis)

((Thomas.Polansek@thomsonreuters.com))