GRAINS-Corn gains on firm cash market, rain-delayed planting

* Corn rises as rains affect already-delayed planting

* Nearby soy retreats as old-crop/new-crop spread narrows

* Traders awaiting further imports of South American soy

(Recasts with U.S. market open, adds quotes, updates prices, changes byline and dateline, previous HAMBURG/SYDNEY) CHICAGO, April 23 (Reuters) - U.S. corn futures advanced for a second straight session on Wednesday, adding more than 1 percent on firm cash markets and as cooler and wetter weather in the central United States stalled planting of the crop in the western corn belt. Soybeans were mixed, with nearby prices pressured by spread trading activity and expectations of more U.S. imports of South American beans amid weak near-term demand from China. Wheat was pressured early in the day on crop boosting rains in parts of the U.S. Plains winter wheat belt before turning higher on short-covering support. "We're looking at some planting delays over the next few days with the heavy moisture," said Rich Nelson, chief strategist with Allendale Inc. "But we are finding some resistance at higher prices as we move above this $5 (per bushel) level in corn," he added. Chicago Board of Trade May corn rose 6- cents, or 1.2 percent, to $5.02-1/4 a bushel by 11:07 a.m. CDT (1607 GMT) in a second straight day of gains after sinking to a three-week low on Monday. A storm system was expected to bring up to an inch of rain to pars of the Midwest through Thursday, including major corn production areas in eastern Nebraska, Iowa and southern Minnesota, Commodity Weather Group said. The storms will further delay planting activity that is already behind the average pace. Cash basis bids rose at some Midwest processing locations, including a large plant in Decatur, Illinois, and one in Cedar Rapids, Iowa. Traders shrugged off data from the Energy Information Administration that showed ethanol stocks rose to their highest level since February despite a large drop in production.

Spot soybeans fell for a fourth straight session for the first time since November, further narrowing an inverse to new-crop prices that hit a seasonal high last week of more than $2.70 per bushel. "Soybeans are still being weakened by the reports of imports into the United States, which may relieve tight U.S. supplies, and concern about low demand in China," said Ole Hansen, head of commodity strategy at Saxo Bank. Two Brazilian soybean shipments originally sold to China by Japan's Marubeni Corp have been switched to the United States, the latest of several U.S. import shipments expected this season. This followed a report China may default on soybean import deals from the United States and South America because of poor domestic demand. CBOT May soybeans dropped 2-1/4 cents, or 0.2 percent, to $14.77-1/2 a bushel while new-crop November added 5-1/4 cents, or 0.4 percent, to $12.20-3/4. CBOT May wheat added 6 cents, or 0.9 percent, to $6.79 a bushel.

Prices at 11:07 a.m. CDT (1607 GMT)

LAST NET PCT YTD CHG CHG CHG CBOT corn 502.00 5.75 1.2% 19.0% CBOT soy 1477.00 -2.75 -0.2% 12.5% CBOT meal 479.70 -0.10 0.0% 9.6% CBOT soyoil 42.54 -0.20 -0.5% 9.6% CBOT wheat 679.00 6.00 0.9% 12.2% CBOT rice 1517.00 -2.00 -0.1% -2.2% EU wheat 214.75 0.00 0.0% 2.8% US crude 101.65 -0.1 -0.1% 3.3% Dow Jones 16,493 -21 -0.1% -0.5% Gold 1284.40 1.40 0.1% 6.6% Euro/dollar 1.3820 0.0017 0.1% 1.2% Dollar Index 79.8190 -0.0860 -0.1% -0.3% Baltic Freight 956 17 1.8% -58.0%

(Additional reporting by Michael Hogan in Hamburg, Colin Packham in Sydney; Editing by Dale Hudson and Tom Brown)