He replaces Sir John Anderson.
It has forecast a lift in full-year operating earnings.
The Christchurch-based company flagged the departure of veteran businessman Anderson last month.
He was appointed to steer the company after its 2010 shake-up that followed the arrival of Agria as an investor with fresh equity at a time profits were weak and debt was high.
Agria subsequently lifted its holding to 50.5% after a takeover offer that was accepted by then major shareholder Pyne Gould Corp and endorsed by Wrightson’s board.
It took a $321 million charge against 2013 profit to write off goodwill and posted a decline in operating earnings that reflected last summer’s drought.
“Solid progress has been made to the foundations of this business over recent years and the challenge now was to use this strength to improve the performance of the business,” Lai said in a statement.
Anderson, in his final speech as chairman, said the company is on track to deliver operating earnings before interest, tax, depreciation and amortisation of $52 million to $56m this financial year.
That would be an increase from the $45.8m EBITDA reported for 2013. Shares in Wrightson last traded at 39 cents and have declined 11% this year.
