A farmer works at a rice paddy field where rice sprouts are covered by plastic sheets for protection against cold weather and strong winds in Bac Ninh province, outside Hanoi January 30, 2013. The Vietnamese government will allow domestic companies to start buying winter-spring rice from next month to build a stockpile equivalent to 1 million tonnes of husked grain to avoid price falls, the official Vietnam News Agency reported. REUTERS/Kham (VIETNAM - Tags: AGRICULTURE BUSINESS FOOD)