Rice±®sh culture systems in the freshwater area
of the Mekong Delta are mainly characterized by the
concurrent culture of rice and ®sh. One ®sh cycle
usually spans two rice crops (each rice crop about
100 days) and a rice ratoon crop. Ratooning is the
ability ofthe rice plantto regenerate new tillers after
harvest (Chauhan, Vergara & Lopez 1985). Because
ratooned rice has a shorter growth duration than a
new rice crop, farmers chose rice ratooning when
hydrological or climatic conditions do not allow for
another normally seeded rice crop.