Crop research. Researchers measuring the amount of natural radioactivity at different heights in a greenhouse. This is part of research to determine how natural conditions affect plant growth. This will help when making changes to increase the crop yield. The greenhouse is part of the Almeria Fruit and Vegetable Exporters Association (COEXPHAL), Almeria, Spain. Since the 1960s, the large-scale use of greenhouses to grow crops has dominated the Almeria region, and is a vital part of the local economy.