A South Australian farmer has written off 1,000 tonnes of potatoes, worth $300,000, after two freak rain events drowned the mature crop.

Terry Buckley received more than 120 millimetres of rain at his Mingbool property, in the state's south-east, and spent Tuesday afternoon frantically pumping knee-deep water out of paddocks to try and save what remained.

"We've only got 36 hours and they're done," he said.

"I'm digging a hole with the excavator and then have three little pumps that we use for this sort of thing.

"It's all about air. As soon as they get their air cut off, they suffocate and die."

For about 50 of his total 900 acres, it's too late.

Just three weeks out from harvest, the vivid green paddocks were turned to brown overnight.

"That should be 1,000 tonnes of potatoes, at $300 a tonne there," he said of three large paddocks.

"It's not good numbers."

The distance between Mr Buckley's 15 paddocks, usually a logistical nuisance, became his saving grace.

"There are days like today you're really glad it's spread around as much as it is," he said.

"The trouble is, there's hardly enough margin in the industry to sustain the losses.

"If you've got a higher margin you can write the crop off now and again but the margin's really not high enough to do that."

Mr Buckley was not covered by insurance, a protection measure he said was too expensive to justify.

"The cost of the insurance is so high, you just have to take the chance," he said.

"Whether it's time it was reinvestigated I'm not sure, but yeah, this is no fun doing what we're doing at the minute."

During the first rain event, on January 7, Mr Buckley said, there was about 48 millimetres of rain in less than 20 minutes.

"I was at one of the paddocks, looking across, you couldn't see the soil anywhere," he said.

"It was just a sheet of water from one side to the other.

"I had hail half an inch across, banging on the top of my ute."

A few days later, throughout the early morning of January 13, the same paddocks were hit by another 80-millimetre downpour.

"I've probably never seen rain that heavy around here before," he said.

"We already lost some spuds last week. Now we've added to that considerably.

"They're very hard to irrigate now 'cos you've got wet bits and dry bits and don't know when to start irrigating again. Life from here is very difficult."

Sporadic rain started falling again on Tuesday afternoon, as a team of men worked to create impromptu dams in three separate locations.

"It's pretty depressing, but you can't dwell on it or you wouldn't go on," Mr Buckley said.

"I think I'm still better off than the people in western Queensland that haven't had any rain for five years.

"Fortunately [my] mother's lambs are paying well. We'll definitely need those."

Source - http://www.abc.net.au