Argentina needs rain by the end of the month to maximize corn yields and to realize forecasts that the global supplier will have a record harvest of 28 million tons, farmers and agronomists say.

Skies have been rain-free over the sprawling Pampas farm belt and meteorologists see only sparse showers on the horizon, raising concern that some fields will not be wet enough for corn plants to take full advantage of their key flowering stages.

Consumer nations, stung by high grain prices, are counting on Argentina, the No. 3 world corn exporter, to help compensate for last year's poor crop in No. 1 supplier, the United States.

Estimates put Argentina's upcoming crop well above the country's biggest ever harvest of 23.8 million tons in the 2010/11 season. The U.S. Department of Agriculture (USDA) upped its estimate for Argentina to 28 million tons last week from 27.5 million tons.

"The harvest could be anywhere between 26 million and 30 million tons," said Melinda Sallyards, agricultural counselor at the U.S. Embassy in Buenos Aires. "To hit the 28 million mark, it would ideally start to rain over the next nine days."

Weather maps show dryness throughout Cordoba province as well as in northwestern Buenos Aires and southern Santa Fe. The Argentine government forecasts a total 2012/13 corn crop of 28 million to 30 million tons.

But if showers do not develop before the end of the month, farmers agree early-planted corn flowering may be stunted. This would hurt yields and fuel worries voiced by the United Nations that food prices will stay high in 2013 due to low stocks.

Corn is widely used in food production and livestock feed. So higher corn prices could drive up prices for a variety of foods, including meat.

"We will start to worry about dryness if we do not get some good rainfall by Jan. 25," said Santiago del Solar, who manages thousands of hectares of corn and soy fields in Argentina's main agricultural province Buenos Aires.

The season started with the opposite problem, when strong August-November storms flooded wide swaths of the Pampas.

The soggy conditions delayed corn seeding and forced some farmers to write off certain fields. But the wetness is also expected to increase yields in the areas that were planted, compensating for the flood-related losses.

"The early-planted corn is outstanding and should give record yields," del Solar said. "The downside is that some areas were flooded and could not be planted, while other areas were seeded much later than usual."

After the record 2010/11 crop, the 2011/12 season was hobbled by a six-week drought that hurt corn plants just as they entered the delicate flowering stage, reducing last year's harvest to 21 million tons.

"This season we've got good soil moisture and we're getting lots of sun with low temperatures at night, which is ideal," said Martin Fraguio, executive director of Argentine corn industry chamber Maizar. "Per-hectare yields will be the highest in our history."

The previous record is 7.8 tons per hectare. Fraguio says they should push closer to 8 tonnes per hectare this year. About three weeks ago, the rains stopped and clouds cleared in most parts of the grains belt.

"So far this has been positive because it reduced excess water and raised harvest expectations by allowing more areas to be planted," said Eduardo Sierra, climate advisor to the Buenos Aires Grains Exchange.

"At this point, it needs to rain immediately in order to avoid thermo-hydric stress on corn plants and hit the 28 million-ton production target," Sierra added. "And the fact is the forecasts show little rain through the end of January and perhaps into the first days of February."

(Editing by Bob Burgdorfer and Marguerita Choy)