AUSTRALIAN wheat growers should tread warily after reports on the prospects of the coming season.

German trader Toepfer International reported that the global market should remain "comparatively comfortable" in the 2012-13 marketing year.

But its outlook depended on production forecasts in the major grain-producing regions remaining relatively unchanged.

Toepfer said there was expected to be a slight increase in the area sown to wheat, but yields were dependent on weather conditions.

It said bigger plantings were expected in the US, Russia, Kazakhstan and European Union countries.

It said relatively mild conditions in Russia should result in a low winter kill rate, boosting grain production.

Plantings in the EU should rise as farmers switch out of canola production in favour of wheat due to adverse weather.

"There is, however, expected to be a significant reduction in acreage in the Ukraine, where wheat was not able to develop well due to a lack of rainfall between mid-August and mid-November, meaning above-average winter kill is expected," Toepfer said.

Wheat growers may have to rely on tight corn supplies to again prop up prices.

But Toepfer was expecting corn prices to ease, due to a probable improvement in yields and a modest increase in the ethanol mandate in the US.

It was forecasting record corn production globally in 2012-13, with the area planted to the crop increasing by a million hectares to 169 million ha.

Toepfer said the price of corn relative to soyabeans on the Chicago Board of Trade tended to favour planting of corn in the midwest of the US.

"There is also expected to be an increase in the Ukraine, as many of the areas lost as a result of the dry conditions are expected to be replanted with corn," it said.

"China is also expected to experience another significant increase in corn planting."

These would be offset by a decrease in plantings in Argentina due to weather patterns, though the US Agriculture Department predicts a slight increase in corn production there.

Toepfer said soyabean forecasts were harder because it would be nine months before the South American crop was sown.

Canola plantings were expected to increase in Australia and Canada as a result of high prices and good recent crops.