Aquaponics is an integrated food production technology of aquaculture and hydroponics. Lettuce (Lactuca sativa L.) is an economically important vegetable crop that can be grown aquaponically. In addition to selecting the right choice of lettuce cultivars, developing an optimal harvest strategy could increase lettuce production. Lettuce production using two harvest methods, Cut-and-Come-Again (CC) and Once-and-Done (OD), was evaluated using 'Red Sails' lettuce in a flow-through aquaponic system rearing trout. With the CC method continual harvesting was possible on a weekly basis after the initial harvest, while it took five weeks for each harvest using the OD method. The total yield of lettuce by the CC method was 6.7 kg from 9 trays, while 22.6 kg of lettuce was harvested by the OD method using 54 trays. In harvests by the OD method, 6 times as many seeds were sown compared to the CC method. The average yield per tray harvested by the CC method (744.4 g/tray) was 78% higher than that by the OD method (418.5 g/tray) because the CC method used 6 times less trays. Productivity, calculated by the average yield per growing week, of the two harvest methods at the first harvest was similar, but 4.8 times higher in the CC method than in the OD method at the second harvest due to the shorter harvest time. However, visual and decay ratings of lettuce harvested by the CC method began to decline afterwards. Together, the OD method after two consecutive harvests by the CC method would help growers to obtain increased yield of quality lettuce.
Aquaponics is the combination of hydroponics and aquaculture that sustainably produces both animal and plant food products. Soluble nutrients are released into water by the fish providing nutrition for plant growth. Lettuce (Lactuca sativa L.) is one of the most popular vegetables grown in aquaponic systems. In this experiment, the feasibility of year-round lettuce production utilizing a cold water flow-through aquaponic system (FTS) growing trout (Oncorhynchus mykiss) in a high tunnel was evaluated. A high tunnel is a greenhouse-like facility constructed with polyethylene covering a metal frame which extends the growing season and protects the crop from cold temperatures. The average night air temperature inside the high tunnel during winter in Wardensville, WV was 2.9±3.4 °C and it helped extend the growing period into the fall and winter. Results from this pilot scale experiment showed the potential for year-round lettuce production in an FTS. Average yield (fresh harvest weight per tray) in the spring season was the highest, while productivity (average yield per week) during the summer season was higher than that in spring. During the extended growing seasons (fall and winter), more than a quarter (30.6%) of the total lettuce production was obtained. The yield per unit area (7.4 kg m -2 ) from our pilot study was significantly higher than that from the reported average field production (3.1 kg m -2 ) in the U.S. except California and Arizona where year-round production of lettuce occurs. To compensate for lower lettuce yields during cold seasons, high value crops requiring less nutrients and tolerant to the colder environment may be considered.
Aquaponics is the integration of aquaculture (the rearing of fish) and hydroponics (the conventional method of soilless farming). Effluent produced from the production of fish can be utilized as a source of nutrients by plants for growth in a hydroponic subsystem. Lettuce (Lactuca sativa) is an economically important vegetable crop that can be grown aquaponically. However, the suitability of lettuce for production in cold water flow-through systems (FTSs) is poorly described. The purpose of this study was to evaluate the growth, market rating, and nutrient uptake of lettuce grown in a cold water FTS. Three objectives were established to examine lettuce production and nutrient uptake in this system: (1) evaluate various lettuce types and cultivars for performance; (2) compare two harvesting methods, cut-and-come-again (CC) and once-and-done (OD), for lettuce yield and market quality; and (3) assess year-round lettuce production in a pilot scale setting for lettuce yield, nutrient removal, and economic viability. To achieve the first objective, 28 lettuce cultivars were grown for ten weeks in aquaponic, hydroponic, and spring water conditions and lettuce productivity was compared. Productivity was calculated by grams of harvestable fresh weight divided by the number of growing weeks until harvest (g•wk-1). Twenty cultivars, 71% of cultivars, showed no difference in productivity between the hydroponic and aquaponic treatment; Only one cultivar, 'Speckled Amish', had higher productivity in the aquaponic treatment compared to the hydroponic treatment. Productivity in the eight of the cultivars was greater in the hydroponic treatment compared to those same cultivars grown in the aquaponic treatment. Maturity of lettuces grown in the spring water control, which had little nutrient to sustain continual growth, was the only rating description with observed differences. Maturity ratings in the spring control were immature. While lettuce types and cultivars were evaluated in objective one, two harvesting methods, CC and OD, were evaluated in objective two. With the OD strategy, all plants in the system are sown and harvested at the same time. After harvest, a successive crop is sown to complete a new growing cycle. With the CC strategy, all plants in the system are sown, but cut above the meristem at harvest to allow for continued growth. A successive crop is sown when the crop no longer continues to produce. There was no difference in productivity between the harvesting methods during the first two harvests. CC productivity declined significantly after that period. Productivity in the CC treatment was better when growing time was incorporated into the final harvest. In addition to evaluation of lettuce types and cultivars and harvest strategies for lettuce production in FTS, seasonal effect on lettuce production and nutrient removal was investigated First and foremost, I would like thank God, who has blessed me with many opportunities and gives me the strength to proceed when there is doubt. To my parents, Tiffani and Garl...
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