Growing Lettuce by a Float-Support Non-Circulating Hydroponic Method in Hawaii and Pennsylvania

摘要

Similar experiments were conducted in high tunnels at Volcano,Hawaii and StateCollege,Pennsylvania.Styrofoam boards (61 x 122 cm) were configured to hold 12 lettuce plantsin net pots.They floated on nutrient solution in a 14 cm deep tank and came to rest on 8,10 and 12cm diameter plastic pipes as nutrient solution was lost by evaporation and transpiration,thuscreating 3 different heights of humidified air spaces.There were also continuously floating andfixed supported treatments.There was only an initial application of water and nutrients.Electricalpower and pumps were not needed for aeration and circulation.Yields from semi-head,romaineand leafy cultivars were similar for the fixed supported,continuously floating and the float-supporttreatments in the Pennsylvania trials.The same was true for leafy and semi-head cultivars in theHawaii trials.However,romaine lettuce yields were significantly lower in continuously floating and8 cm float-support treatments than fixed supported and 10 and 12 cm float-support treatments in theHawaii trials.Heads were allowed to develop to a larger size in the Hawaii trials,because boltingwas not a serious threat in the cool upper elevation climate.