Nikiski grower JD Megchelsen and his record-breaking pumpkin "Thunder Horse". Picture: Kenai Peninsular Online

Only a forklift could move a massive 707lb (320.6kg) pumpkin that doubled the previous record at the Alaska State Fair last week.

Nikiski grower JD Megchelsen's record-breaking vegetable "Thunder Horse", standing 3ft (91.5cm) high and measuring 4ft (121.9cm) across, was transported to the fair in a pickup truck. The pumpkin was covered with a quilt and connected to water tubes, Associated Press reported.

On July 9, Thunder Horse weighed 22lb (10kg), but by August 1 it had ballooned to more than 400lb (181kg). At its peak, it was gaining more than 60lb (27kg) a day.

Megchelsen said his fast growth secret had a lot to do with new seed varieties, new cultivation methods and even the internet, as pumpkin growers around the world were sharing their knowledge.

Despite his record-breaking farming feat, Megchelsen is a long way off the world record, which was set last year in Oregon at 1385lb (628kg).