Abstract
Vegetable production in greenhouses through the winter months presents various difficulties. One of them is the lack of enough solar radiation to ensure the normal development of the plants. The comparison of the lighting conditions between Bulgaria and the Netherlands, where supplementary lighting is applied, shows that despite our more favourable geographical location, they are almost the same. During the typically winter months the requirements for the main greenhouse vegetable crops are not provided tо a sufficient extent and that is why the application of supplementary lighting is needed. Application of supplementary lighting under the conditions of insufficient amounts of natural light significantly increases the growth, development and productivity of the plants. The expenses for the production of the crops compared with the traditional method are decreased and, at the same time, the yields and intensity of the production are increased, and that defines the promising outlook of this technology.
Key words: supplementary lighting, vegetables, greenhouses