* Q1 revenues up nearly 21 percent to $11.7 billion
* Energy, agricultural profits down from a year ago
CHICAGO, Jan 10 (Reuters) - CHS Inc, the largest U.S. farm and refining cooperative, said on Thursday its quarterly earnings fell 17 percent from a year ago, hurt by lower margins at its petroleum refineries in Montana and Kansas.
The St. Paul, Minnesota-based food and energy company said net earnings were $343.7 million for the quarter ended Nov. 30, down from $416.2 million a year ago.
Revenues for the first quarter of fiscal 2013 rose to $11.7 billion from $9.7 billion.
CHS is a major food exporter and processor, a supplier of crop nutrients to farmers and food ingredients for manufacturers, and operates petroleum refineries and pipelines in the United States.
CHS energy segment led results but earnings were down from a year go due to lower margins at its U.S. oil refining plants in Laurel, Montana, and McPherson, Kansas. Combined the two plants produce about 5.9 million gallons of fuel per day.
Profits from its agricultural business sector also fell, reflecting a drop in the amount of grain and oilseeds the co-op handled during the quarter as well as reduced fertilizer sales.
The drop in grains and oilseeds volume comes as CHS and other agribusinesses continue to face the fallout from last year's U.S. drought - the worst to hit the United States, the world's top food producer and exporter, in more than 50 years.
CHS processing and food ingredients earnings were up on the quarter as soybean processing margins improved.