Former studies show, that lighting is the main tool when grower aims to lower nitrate levels. Since the iceberg lettuce is the main salad type grown in Finland, the latest field test was run by comparing 3 different iceberg type lettuce varieties in same growing environment during winter growing season. Results show that the nitrate levels of all the tested varieties were far below the limits set in EU regulation. However, one was clearly the winner with very low nitrate level – Finstar. Results indicate, that different varieties would need more specific growing recipes and that with right spectrum of lighting, very low nitrate levels can be achieved even during the winter time. Other interesting outcome was the form of ready salad head. When more and more professional greenhouses have automatized harvesting and packing, the form of salad is a crucial factor in cutting and packing processes. This study shows that under these growing circumstances, the variety Viivi (LX511) grew in most nice and compact form in terms of packaging.
