* Planting starts 10 days earlier than last season
* Brazil seen producing record soy crop
* 30 mm rain expected in coming days in Mato Grosso (Adds rain forecast, outlook for second corn crop, analyst quote`,s, Chicago prices)
By Roberto Samora and Caroline Stauffer
SAO PAULO, Sept 21 Farmers in Brazil's grain belt jump-started planting after early showers set the scene for what is expected to be a bumper corn and record soy crop, producers and analysts said on Friday.
If rains continue in the coming weeks as forecast, Brazil could churn out 81 million tonnes of oilseed and replace the drought-stricken United States as the world's top soybean producer, according to the U.S. agriculture department.
Strong and early 2012/2013 grains harvests from Brazil and neighboring Argentina would be welcome by food importing nations since lower U.S. production forecasts have driven up prices and stirred supply fears.
Farmers have sowed 0.6 percent of the projected area to be planted in top soy producing Mato Grosso state, where planting started 10 days earlier than a year ago, the privately-owned Mato Grosso Institute for Agricultural Economy (IMEA) said.
"There is planting going on throughout the state, except the Northeast where planting is usually done later anyway," Cleber Noronha, an analyst at IMEA, told Reuters.
COLD FRONT MOVES IN
A cold front brought 20 millimeters of rain to Mato Grosso in the past week, not necessarily enough to soak soils after a very dry August, but 30 additional millimeters of rain expected in coming days should do the trick, Somar Metorologia said.
"Farmers who already started to plant should not be punished, given our forecast," said Flavia Matiolio, a meteorologist at private forecaster Somar. The company feeds weather outlooks to local media, private companies and government studies in Brazil.
Brazil has harvested high-yielding crops in years when dry weather forced farmers to plant later in the season, but September sowing means harvesting can begin as early as January.
That schedule allows for smoother transport to Brazil's ports and timely exports. It also gives farmers ample time to plant second crops of corn and cotton, enjoying maximum productivity from Brazil's tropical growing season.
Brazil is now the world's No. 3 corn exporter, thanks mostly to increased output from the second of two annual corn crops. That crop, known as the safrinha, grew by 70 percent this year from a year earlier and the government says 2011/2012 corn exports should reach a record 16 million tonnes.
"Farmers want to get a head start on planting to take advantage of the second crop window... corn can be planted until Feb. 20," said IMEA's Noronha.
Local analysts expect an unprecedented soybean comeback in Brazil this year, with weather forecasts, prices and a favorable exchange rate encouraging bets on soy after drought left a disappointing 65-million-tonne crop last season.
On the low side, Minas Gerais-based analyst Celeres expects Brazil's overall soy crop to produce a record 78.1 million tonnes, while Safras e Mercado foresees an 82.3-million-tonne crop. Brazil's government starts official forecasts on Oct. 9.
Brazil's farmers, hoping to cash in on high soybean prices spurred by supply concerns, have already sold 46 percent of the 2012/2013 crop through forward sales.
The country's area planted with soy is expected to increase by more than 8 percent from last season to 27.14 million hectares, according to local analyst Celeres. That would be one of the biggest annual jumps in planted area in nearly a decade.
"A large area planted, favorable weather forecasts, high prices... producers are investing in technology, so we should have an exceptional soy harvest this year," said Flavio Turra, an economist at cooperative Ocepar, which represents producers from Brazil's No. 2 soybean producing state Parana.
"Today it is raining in various places and it looks like the people who haven't done so already will plant," he said.
Corn and soybean prices edged higher in Chicago on Friday, modestly limiting what looks to be big weekly losses. Crop reports showing the U.S. harvest was not as bad as originally thought and rain forecasts in South America helped grains prices ease off all-time highs this week.
CBOT November soy rose 0.22 percent or 2-3/4 cents to $16.21 a bushel on Friday while CBOT December corn added 0.47 percent or 4-1/4 cents at $7.5-1/4 a bushel. (Editing by Dale Hudson, Phil Berlowitz and Tim Dobbyn)