Non-circulating Hydroponic Methods for Growing Tomatoes

‘Big Beef’ tomatoes produced 2.68 kg/plant from a 72 day harvest period when they were grown in 0.35 liter aluminum beverage cans by a sub-irrigation hydroponic method. Tomatoes growing in net pots (70 ml) suspended by expanded polystyrene bead boards with a sub-irrigation method gave similar yields in one trial but lower yields in another trial than tomatoes growing in beverage cans. Tomatoes growing in 10 cm square plastic pots filled with perlite (700 ml) rested on 5 cm high upside-down nursery trays and yielded significantly higher than plants growing in aluminum beverage cans resting on the tank floor in 2 trials. Placing a 5 cm high nursery tray as a support for a 10 cm pot increases the root exposure to moist air (i.e. air between the nutrient solution surface and the tank cover) and provides a net-type surface which encourages root formation and anchorage. Hawaii’s lower elevations are warm and very conducive to mosquito reproduction in these non-circulating hydroponic tanks. In an effort to control mosquitoes, window screen was supported on the nursery tray above the nutrient solution level, thus trapping newly hatched mosquitoes below the screen where they eventually died. Tomatoes were also grown in 7.6 liter pots which were sub-irrigated by microtubes. Each pot contained an upside-down 3.8 liter pot with slits, so only 3.8 liters of cinder growing medium was needed to fill the pot. In several cases, roots grew into the microtubes supplying the nutrient solution and this blocked nutrient flow to the pots, thus killing the plants. Tomatoes growing in both of these mosquito-proof systems yielded similarly when protected by a simple polyethylene rainshelter from 158 cm of rainfall during the growing period, but unprotected tomato plants yielded 55 per cent lower in the pot-screen-tank system and no salable yields were obtained from the unprotected sub-irrigated 7.6 liter pots.