Mr O'Sullivan works on his family's 1000-cow dairy farm near Pleasant Point and also works with an irrigation design consultancy and co-owns a company specialising in irrigation- and effluent-pond liners.
His first prize package is worth more than $90,000, and includes a $52,990 Hyundai Santa Fe 2.2 seven-seater vehicle, a $15,250 Honda TRX420 four-wheel farm bike, $9000 worth of Ravensdown products and services, $7000 worth of ECHO equipment and $5000 cash from the National Bank.
Otago-Southland representative Richard Copland (30), of Gore, finished just four points behind Mr O'Sullivan and won $21,600 worth of prizes including a $5000 Lincoln University tertiary study scholarship.
Although disappointed he did not achieve his goal of winning the final in front of friends and family who had travelled to the occasion, he was pleased to finish second.
Mr Copland farms a 240ha sheep and deer farm in partnership with his parents and has shares in a dairy farm.
Chris Will, from Rongotea, Manawatu, finished third and Andrew Morris, of Morrinsville, fourth.
Next year's Young Farmers final will be held in Gore.