The hydroponic production of lettuce (Lactuca sativa L) by using hybrid catfish (Clarias macrocephalusxC. gariepinus) pond water: Potentials and constraints

An experiment was conducted at the Asian Institute of Technology, Thailand, for 54 days to investigate on the effect of pond water filtration and aggregates (hydroponic substrates) on lettuce (Lactuca sativa L.) production, nutrient uptake and growth. A 2x3 factorial experiment consisting of 2 filtration regimes (unfiltered versus partially filtered pond water) and 3 aggregates (styrofoam as control, sand, and gravel). The hydroponic units were placed on a bamboo platform across the pond surface. An earthen pond (226m2) was stocked with 8000 hybrid catfish with an average initial weight of 6.58±1.72g. The fish were fed with commercial pelleted feeds containing 30% crude protein. Twenty-one days old lettuce seedlings were transplanted on to hydroponic units after stocking catfish for 4 months in the pond. Pond water was partially filtered by using a settling tank and filtration tank, which contained netting materials to trap solids. Lettuce plots were irrigated twice daily at 0800 and 1600h using either filtered or unfiltered pond water for 45min. The highest head weight and yield of lettuce were observed with plants grown on the sand media followed by gravel and the control treatments. Partially filtered pond water treatments had significantly higher lettuce yield (P