DuPont Co. doubled its profit in the fourth quarter as the company benefited from significant revenue growth in its agriculture segment, Fox Business News reported. The Delaware-based company also announced a $5 billion stock buyback plan, to include $2 billion in stock to be repurchased this year. DuPont reported net income of $185 million, or 20 cents per share, compared with $92 million, or 9 cents per share, for the fourth quarter of 2012. DuPont's agriculture business, Johnston-based DuPont Pioneer, set the pace with revenue of $1.81 billion, up 18 percent year-over-year.