2.3. Water and irrigation system
The effluent used as irrigation water came from a 100 m2
pond, that was fertilized with 10 kg of chicken manure before
stocking the tilapias (Oreochromis niloticus) in a density of
2.5 fish/m2. The fish were fed ad libitum two times a day with a
commercial diet containing 28% crude protein. Chemical
analyses of water and effluent were performed (Table 1). A drip
irrigation system was used with auto-compensated drippers at a
flowing rate of 2.3 L/h, spaced 0.5 m apart, with a filtration
system composed of two 120 mesh plastic disc filters. The
estimate of the irrigation requirement was performed on the
basis of the crop coefficients (Kc) recommended by FAO (Allen
et al., 1996) and evapotranspiration data from ESAM
Meteorological Station, located approximately 700 m from
the experiment site. The amount of water and nutrients was
recorded (Table 2). The adopted irrigation schedule was of
50 min per day throughout the entire crop cycle, being 25 min
in the morning and 25 min in the afternoon. Emitters were
sampled every other week and tests were performed to monitor
flow rates.