Grain growers in the United States are facing their worst wheat harvest in more than 50 years.

Prolonged drought followed by heavy rain has slashed yields throughout the country's wheat belt.

US market analyst Arlan Suderman, from Illinios, says he's tipping an increase in wheat prices as US farmers abandon their crops.

He says Kansas' primary wheat producing area is facing a bleak outlook this year.

"I'm 54 years old now and this is probably the worst crop I can remember seeing in my life," he said.

"In the high plains of Kansas, Oklahoma and Texas, a lot of yields are below 10 bushels per acre and many of those fields are simply stopping and calling their insurance agent and want to leave the residue behind to help hold the soil," he said.

Mr Suderman says while hard red winter wheat yields will be down, protein and quality levels should remain high.

He says the US' soft red winter wheat yields will be higher and will compete with grain from the Black Sea and European Union.

"We often talk in the United States about the dirty '30s," Mr Suderman said.

"We had a 42 month period of extreme drought in the great plains of the United States.

"Many areas of the plains this year wrapped up a 42 month period that was even drier than that period back in the 1930s.

"This is a drought that's been one of our worst droughts in the last 80 years or more and it just made it really difficult for the crop to ever get established."

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