A third of the population of Swaziland will need food aid after the 2007 maize harvest was the lowest on record.
Swaziland has become dependent on food aid
The harvest follows a prolonged dry spell and high temperatures.
A United Nations assessment mission says some 400,000 people will need some 40,000 tonnes of food assistance before the next harvest in April 2008.
The situation is blamed on increasingly erratic rainfall, inappropriate farming strategies and declining numbers of farm workers as a result of Aids.
FAO economist Shukri Ahmed, who has just returned from assessing the situation on the ground, said the situation had been deteriorating year-on-year, but the estimated 60% drop in production this year was not only because of poor rainfall.
"The farmers are also not using the right crop mix... The government needs to accelerate projects involving crop diversification, small-scale irrigation projects and encourage water harvesting," he told the UN news agency.
The joint assessment mission to Swaziland by two UN agencies - the Food and Agriculture Organization and the World Food Programme - is the first in a series being conducted in southern African countries.