|Authors: ||N. Toth, R Vrhovec, J. Borošić, B. Benko, S. Fabek, I. Zutić, S. Radman|
|Keywords: ||Lactuca sativa var. capitata, hydroponics, abiotic factors, relative growth rate, head mass, yield|
Floating system and management of abiotic factors in the greenhouse achieved the optimal lettuce growth.
Aim of the research was to select the combination of cultivar and plant density (stand) which meets the market requirement of lettuce head mass (200-300 g) and provides the highest yield.
Five lettuce cultivars ('Tourbillon', 'Othilia', 'Maritima', 'Caipira', 'Bonaly') and 3 stands (13, 17 and 21 plants m-2) were tested by method of randomized block design with three replications.
Lettuce was sown on July 31 and the seedlings were deployed on polystyrene floaters on August 18 (100 plants m-2) and redeployed on August 28 at scheduled stands.
Morphometric analysis of lettuce was conducted five times during the growing period and also at the harvest on September 20. During the production cycle the mean air temperature was 22.3°C, while relative humidity ranged from 39 to 80%. Parameters of nutrient solution were: temperature 22.7°C, dissolved oxygen 7.8-8.3 mg L-1, pH-value 6.1 and EC-value 1.3-1.7 dS m-1. Relative growth rate was higher at the start of growing period, i.e., the younger plants were grown faster.
Adequate lettuce head weight (276 and 321 g) was recorded by stands of 17 and 13 plants m-2. The highest marketable yield was achieved by combinations: 17 × 'Bonaly' and 13 × 'Tourbilon' (4.07 and 4.17 kg m-2, respectively). Combinations of 'Bonaly', 'Othilie', 'Tourbilon' and 'Maritima' with stand of 17 plants m-2 can be recommended since they provided satisfactory head weight for sales per piece and thus a higher income per unit area compared to other combinations.
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