ISHS Acta Horticulturae 133: Nutrient Film Technique and Substrates, XXI IHC
GREENHOUSE LETTUCE PRODUCTION AT HIGH DENSITIES IN HYDROPONICS |
| Authors: | J.V. Morgan, A. Tan |
| Abstract:
An archway concept is described for the production of lettuce at high densities in hydroponics. Growing tubes are arranged in horizontal tiers sloped to provide for effective solution recirculation. The arch framework at ca. 280 cm wide and 230 cm to the apex is designed for use in a Venlo structure. The arch configuration doubles the cropping surface so that densities of 40 plants/m2 are obtainable and some 8 crops per season are possible. Propagation begins with the covering of level trays/benches with readily-decomposable moistened tissue paper. The area is then covered with 12.5 mm polystyrene sheets in which 10 mm holes are drilled at 35 mm intervals. A pelleted seed is deposited in each hole and after germination occurs complete nutrient solution is introduced to provide a depth of 2–3 mm of recirculating solution. Within 16–20 days the paper has broken down and seedlings with 4–5 true leaves are transferred to the growing tubes without root damage. Plants are spaced 20 cm apart in the 30 mm diam. plastic tubes. No further cultural work is necessary until harvesting. The propagation, planting and harvesting operations are easily mechanised. Data are presented to illustrate the influence of solution temperature, specific conductivity and nitrogen and potassium levels on growth and development during the propagation and growing-on stages. The advantages of the technique over the traditional soil production method are outlined. | |
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