Three non-circulating hydroponic methods for growing lettuce are described which
do not require electricity, pumps or wicks. All of the nutrient solution is added prior to
planting or transplanting. In the simplest system, lettuce is seeded in a tapered plastic net
pot filled with growing medium and placed in a darkened, 4-liter plastic bottle filled with
nutrient solution with the lower 3-cm-portion of the pot immersed in nutrient solution.
Plants are automatically watered, because the entire growing medium in the net pot
becomes moistened by capillary action. Plant growth reduces the nutrient solution level,
creating an enlarging moist air space. Meanwhile, the root system expands and continues to
absorb water and nutrients. Leaf and semi-head lettuce cultivars are usually harvested at
about 6 to 7 weeks after seeding. A typical expansion of this concept to a commercial scale
employs a 14 cm high tank lined with polyethylene sheeting which is filled with nutrient
solution and covered with an expanded or extruded polystyrene sheet resting on the tank
frame. Lettuce is planted or transplanted into net pots filled with growing medium and
placed in holes in the cover. Lettuce seedlings are initially watered by capillary action, and
later, by direct root uptake. The crop is harvested before the nutrient solution becomes
exhausted. Another modification of this method is a float-support system in long
rectangular raceway tanks. Lettuce is planted or transplanted into net pots placed in a sheet
of extruded polystyrene. The cover initially floats on the nutrient solution, and then,
comes to rest on 2 parallel plastic pipes (10 cm diam) resting on the tank floor as the
nutrient solution level recedes due to plant growth. The tank is filled with water
immediately prior to harvesting and floating rafts may be easily moved to a harvesting
station.
Three non-circulating hydroponic methods for growing lettuce are described whichdo not require electricity, pumps or wicks. All of the nutrient solution is added prior toplanting or transplanting. In the simplest system, lettuce is seeded in a tapered plastic netpot filled with growing medium and placed in a darkened, 4-liter plastic bottle filled withnutrient solution with the lower 3-cm-portion of the pot immersed in nutrient solution.Plants are automatically watered, because the entire growing medium in the net potbecomes moistened by capillary action. Plant growth reduces the nutrient solution level,creating an enlarging moist air space. Meanwhile, the root system expands and continues toabsorb water and nutrients. Leaf and semi-head lettuce cultivars are usually harvested atabout 6 to 7 weeks after seeding. A typical expansion of this concept to a commercial scaleemploys a 14 cm high tank lined with polyethylene sheeting which is filled with nutrientsolution and covered with an expanded or extruded polystyrene sheet resting on the tankframe. Lettuce is planted or transplanted into net pots filled with growing medium andplaced in holes in the cover. Lettuce seedlings are initially watered by capillary action, andlater, by direct root uptake. The crop is harvested before the nutrient solution becomesexhausted. Another modification of this method is a float-support system in longrectangular raceway tanks. Lettuce is planted or transplanted into net pots placed in a sheet
of extruded polystyrene. The cover initially floats on the nutrient solution, and then,
comes to rest on 2 parallel plastic pipes (10 cm diam) resting on the tank floor as the
nutrient solution level recedes due to plant growth. The tank is filled with water
immediately prior to harvesting and floating rafts may be easily moved to a harvesting
station.
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