Integrated use of Azolla in irrigated rice fields

Wild species of freshwater fish used to flourish in irrigated rice fields in various parts of the Philippines, but the development and use of pesticides has triggered their disappearance. They began to reappear in the early 1970s, and efforts were subsequently initiated to increase fish harvests in irrigated rice fields. This paper describes field trials to determine the benefits of integrating rice and fish using azolla as a nitrogen fertilizer for rice and a feed ingredient for fish. Azolla could be used to provide 30% of the nitrogen normally provided by inorganic fertilizer. A homemade feed formulation using dry azolla meal was as effective for fish as a commercial feed. Polyculture of common carp and tilapia produced higher fish yields than tilapia alone. The integration of fish and rice produced higher net incomes over the short term, but longer term benefits must still be evaluated.