INTRODUCTION 3

fruits with blossom end rot and 2 % fruits with damage from lighting). Especially, when interlights were lowered in between the rows, the amount of unmarketable fruits (damage from lighting) increased. It seems that sugar content and taste of fruits were not influenced by the lighting regime.

A higher light intensity resulted in same number of internodes at a lower average distance of internodes and consequently smaller plants. However, DM yield of stripped leaves, cumulative DM yield (yield of fruits, leaves, shoots) and N uptake by plants increased with light intensity.

Energy is converted less efficiently into yield at higher light intensity than at lower light intensity. Also, the profit margin was highest at a lower light intensity; especially with the combination “high light intensity and low stem density” profit margin decreased notably. This was attributed to high expenses (of about half of the expenses) for the investment into lamps and bulbs and the electricity itself. Future speculations regarding energy prices are highlighting the importance for growers to get subsidisation from the government and also the need to reduce production costs. Possible recommendations for saving costs other than lowering the electricity costs are discussed.

With respect to a light intensity adapted plant density, it is supposed that at higher light intensities, a higher stem density should be used to have a positive effect on yield. However, from the economic side of view a low light intensity would be recommended. Hence, with increasing solar irradiation vegetable growers could possibly decrease supplemental lighting without a reduction in yield and thus lowering energy costs.