Controlled environment agriculture (CEA)

CEA is a system to modify plant growth environment so that the production season can be extended and/or the plant productivity can be maximized with minimum input of resources. CEA has been used for strawberry production worldwide but less intensively in the US.  CEA enables the growers to control both aerial and root zone environmental conditions. Hydroponics (or soilless culture) takes the most important role in root zone environmental control to optimize water, oxygen and fertilizer input for desirable outcomes (productivity and produce quality).

Fruits and vegetable crops such as tomato, cucumber, pepper, lettuce and strawberry are the major crops commercially produced in greenhouse soilless cultures in many countries worldwide. In the US, introduction of greenhouse soilless culture has been the most successful for tomato, as nearly 40% of tomatoes available in U.S. retail stores are from North American greenhouses (Cook and Calvin, 2005) and approximately 70% of total greenhouse area is used for hydroponically producing tomato (USDA 2009). In addition to the high quality and yields, use of soilless culture systems can reduce the use of fertilizers and water significantly. Use of systems like a raised or suspended trough for strawberry can create better working environments as laborers do not need to stoop to work with plants and to harvest fruit.

While it is unrealistic to expect that all fruiting vegetable growers can move out from the open-field cropping systems, this technology should be utilized more effectively by growers who have no other alternatives to become sustainable. Growers in rapidly urbanizing areas are in need of an advanced technology to survive in this transition. There are ranges of technologies and innovations in soilless culture and greenhouse food crop production. Investments range from $2 to $20 per sq ft, or from a wooden-framed plastic-covered simple structure to a more sophisticated aluminum-framed glass-covered structure with integrated climate control system. The example of the former is the so-called high tunnel, and the example of latter is Dutch Venlo-style high-guttered greenhouse. Greenhouse strawberries in East Asian countries are typically grown in the ‘low-tech’ version of structures (including unheated high tunnels).

Basics of environmental control systems relevant to strawberry production

1. Greenhouse glazing (overall transmission, PAR, UV, NIR, diffuse and overall heat transfer)

2. Heating (overhead heating, target area heating, root zone heating, crown heating, and fuel source)

3. Ventilation (natural ventilation, forced (mechanical) ventilation, insect screen, chimney effect, vent size and location)

4. Evaporative cooling (pad and fan system, high pressure fog system)

5. CO2 enrichment (source of CO2, controlling strategy)

6. Supplemental lighting (photosynthetic lighting, photoperiodic lighting)

7. Shading

8. Air circulation

9. 9.Irrigation and fertigation (drip irrigation, lysimeter, recycling nutrient solution)
   

(Updated 8/5/13)