Pumpkins lay in the backs of trucks at the start of the competition./ Chronicle photo by Lea Suzuki

A forklift helped move a stay-at-home dad's gigantic pumpkin at a US coastal city's annual pumpkin weigh-off this week.

Thad Starr of Pleasant Hill, Oregon entered his 1,524lb (691kg) pumpkin at the Half Moon Bay, California contest on Monday and won USD9144 in prize money, the San Francisco Chronicle reported.

Starr said he had no "big secrets" but used "yards and yards of chicken manure, lots of mixed compost and lots and lots of time".

According to the paper, the world record is a 1,689lb (766.1kg) pumpkin grown by Joe Jutras of Rhode Island this year.

The winning pumpkin will be displayed this weekend as part of the Half Moon Bay Art and Pumpkin Festival.