The index averaged 230 points in March 2011, down 2.9 percent from its peak in February, but still 37 percent above March of last year.
"The decrease in the overall index this month brings some welcome respite from the steady increases seen over the last eight months," said David Hallam, director of FAO's trade and market division. "But it would be premature to conclude that this is a reversal of the upward trend," he added.
Hallam said the picture would become clearer in coming weeks as information on new crop plantings filters through.
However global factors mean uncertainty is not likely to ease any time soon.
"Low stock levels, the implications for oil prices of events in the Middle East and North Africa and the effects of the destruction in Japan all make for continuing uncertainty and price volatility over the coming months," said Hallam.