As of 4 May, 1kg of rice cost 2,500 riel (US$0.61), against 3,200 riel ($0.78) a year earlier, according to the Economic Institute of Cambodia.
Declining food prices are creating difficulties for farmers who need to pay off debts, raising fears that urban workers returning to the countryside will not find work in the agricultural sector.
"Back-to-back effects of, first, the high food price crisis of last year and now the economic slowdown are likely to not only create categories of new poor... but also push into deeper food insecurity the already chronically poor," Jean-Pierre de Margerie, Cambodia country representative for the UN World Food Programme (WFP), told IRIN.
"Last year, a majority of poor households facing higher food prices had to resort to very damaging coping mechanisms such as contracting new debts or even cutting back on food consumption," he added.
Acute malnutrition in poor urban children increased to 15.9 percent in 2008 from 9.6 percent in 2005, as poor families cut back on food expenditure, according to the 2008 Cambodia Anthropometrics Survey, released in February by the government.
More women are also forgoing proper nutrition and healthcare during pregnancy, raising the risk of death during childbirth, the UN said in its 8 April statement.
Five pregnant women die every day in labour, giving Cambodia one of the highest maternal mortality rates in Asia at 472 deaths per 100,000 births, according to the most recent government data from 2005.
The World Bank expects growth to shrink to minus 1 percent in 2009 - the lowest in a decade after average growth of a record 10.5 percent since 2005, mirrored in Phnom Penh's construction and property booms.
About one-third of Cambodia's 14.5 million people live below the national poverty line of $0.50, according to government statistics.
In 2009, another 200,000 people could fall below the World Bank's regional poverty line of $1.25 a day - the highest number in Southeast Asia - it announced in April.
Food insecurity and retrenchment will result in rising child malnutrition and maternal mortality rates, the UN has warned.
Falling demand for clothing from the US and European Union and dwindling foreign investment have cost at least 60,000 garment jobs nationwide and 25,000 construction jobs.
Between 80 and 85 percent of garment workers are women, according to the International Labor Organization (ILO).
"When faced with layoffs, most workers will consume much of their savings while looking for a new job," Tuomo Poutiainen, ILO's chief technical adviser in Cambodia, told IRIN.
Many will ultimately return to the countryside, he said.
Poor families will also cope by removing children from school to work and selling household assets or land, the UN warned, although it was too early to provide figures.
Joblessness could pressure women and children into sex trafficking, hindering the progress made in the past decade against sexual exploitation, the statement added.
To cushion these effects, the government has announced it will release $25 million to the agriculture and garment sectors for training programmes.
"The economic downtime, when people are searching for jobs, can be used to enhance their existing skills or to train on new ones that will help them find work," Poutiainen said.
"In this way Cambodia will have a much more competent and productive labour force after the downtime ends," he said.
A report by the UN Economic and Social Commission for Asia and the Pacific (ESCAP), Sustainable Agriculture and Food Security in Asia and the Pacific, released on 24 April, recommends policymakers enact work-for-food schemes that guarantee employment, encourage poor people to grow private gardens rather than rely solely on income, and establish common property rights over water.