Protected Edible Crops

Tomatoes are the most important crop in terms of market value (84 million EUR, Defra statistics), followed by cucumbers (45 million EUR), lettuce (26M million EUR) and sweet pepper (14 million EUR). Other protected edible crops (excluding mushrooms) account for 21 million EUR.

Most of the protected edible crops are grown in heated glasshouses that are computer controlled so that the aerial environment can be precisely controlled. Boilers or increasingly combined heat and power plants (which produce electricity for the National Grid) provide heat and carbon dioxide. Carbon dioxide concentrations are often enriched to increase photosynthesis and hence yield. Most crops are not grown in the soil, instead hydroponic growing methods are used. This usually involves growing plants on stonewool fibre or in channels in which nutrient solution flows. However, some growers have recently returned to growing crops in soil, so as to obtain organic status.

Few pesticides are used in modern production systems. This is possible because of the introduction of natural predators and parasites, bred for this purpose by specialist companies. Furthermore, bumble bees are introduced to houses to pollinate flowers.

Research on protected edible crops at Warwick HRI is funded by Defra, the Horticulture Development Company and commercial companies. The site is equipped with modern glasshouses equipped for growing semi-commercial crops as well as a range of controlled environment facilities.