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ISHS Acta Horticulturae 458: International Symposium on Water Quality & Quantity-Greenhouse

WATER UPTAKE BY TOMATO PLANTS GROWN IN CLOSED HYDROPONIC SYSTEMS DEPENDENT ON THE EC-LEVEL

Authors:   D. Schwarz, R. Kuchenbuch
Keywords:   Lycopersicon lycopersicum, Nutrient Film Technique, salinity, transpiration coefficient, water uptake efficiency
Abstract:
In recent years the salinity of hydroponic nutrient solutions used in the production of high-quality fruit vegetables such as tomatoes has increased. The aim of the present study was to determine the effect of the concentration of the nutrient solution, controlled as electrical conductivity (EC), on water uptake of tomato (cv. Counter) in closed hydroponic systems. The hypothesis that higher EC-levels result in decreased water uptake was tested in a small scale as well as in a large scale experiment, i.e. under commercial conditions during a 6-month period. EC-levels between 1 and 9 dS m-1 were used.

Tomato growth and yield decreased with increasing EC. At 6 dS m-1, yield was 50 % that of plants grown at 1 dS m-1. Dry matter content of the fruits, however, increased with increasing EC. Water uptake was also reduced with increasing EC independent of related parameters such as growing area or leaf area. At 9 dS m-1 water uptake was reduced to 60 % compared to plants at 1 dS m-1. Reduced water uptake was mainly the result of a decrease in leaf area. At an EC of 9 dS m-1, the leaf area was 20 % less compared to plants grown with the lowest EC. However, changes in growth, leaf area and water uptake were caused by both total solar radiation and EC level and their interactions. The transpiration coefficient decreased with rising EC for the total dry weight, however, when compared to the yield it increased.

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