Tomato (
Solanum lycopersicon esculentum L.) was grown on rockwool at different EC-regimes. The experiments were carried out under different climatic conditions. The EC-regimes were realized by varying the quantities of nutrient elements supplied. The ratios between the elements were kept constant.
The maximum value of the EC in the root environment at which no yield depression occurred was about 2.5 dS.m–1 at 25°C. Higher EC-values decreased the yield with 5 to 7% per dS.m–1. However, a decrease of 10% was found in an experiment with a very high humidity level. High EC-values under poor light conditions did not affect yields adversely to any extent. It could therefore be concluded that in calculations of EC-induced yield reductions from data of experiments with varying EC-values, both the lengths of the EC-intervals and the light intensity during the intervals have to be taken into account.
Fruit quality was improved by increased EC-values. Potassium contents in the leaves were increased and calcium and magnesium contents were decreased. The effect on the nitrate and the phosphate contents was different for young and old leaves.
Key words climatic conditions - EC-values - quality - tissue analysis - tomato yield