Controlled environment structures for strawberries grown commercially use distinct types of structures.
High tunnels (AKA table-top systems)
Indoor farms (without sunlight, as shown in the photo below)
Soilless production systems
Soilless substrate based production system is the most widely used commercially. Other soilless/hydroponic systems can be used but productivity seems to be limited in water-culture-based production systems (such as NFT and deep water culture). Regardless, production systems are designed so that workers stand instead of bending over the crops, improving worker efficiency.
Table-top production systems
Soilless substrate based production system using a simple raised gutter supported by a leg structure anchored in ground is called ‘table-top system’. Table-top systems are typically placed inside a simple structure such as rain shelters or high tunnels. This system is widely used in Europe and is slowly being introduced in North America.
On top of these gutters, plants are typically grown in containers or bags, filled with selected soilless substrates. Nutrient solution is delivered through a drip irrigation system controlled by timers and solenoid valves.
Greenhouse hanging gutter systems
Steel hanging gutters similar to those used for high-wire production are available for strawberry. A typical spacing between gutters is 0.8 – 1.0 meters (center-to-center). On top of the gutters, containers and bags filled with soilless substrates are placed with drip irrigation systems.
Strawberry raised trough systems
This is a minor system in North America but a major system in Japan and other Asian countries. Plants are grown in troughs filled with selected soilless substrates. The trough width is typically 20-30 cm with ~15 cm depth and can be of any length. High density Styrofoam (polystyrene) troughs are used to improve the root-zone temperature stability. Plants tend to grow better in an unrestricted root zone with substrate of optimum physical and chemical characteristics, in our observation.
Nutrient film technique (NFT) has been tested in commercial production but it never became a reliable standard. The reason NFT use is limited may be associated with the long production cycle of strawberry and that NFT is a risky system with little buffering capacity upon any system failures. According to Van Delm et al. (2016), NFT was successfully used for strawberry in late 1970s to early 1980s in the UK, Belgium and the Netherlands but the use rapidly declined as the system was not suitable for their major cultivar highly susceptible to Phytophthora disease. NFT channels are available in various sizes, and NFT for strawberry employs a wide channel to assure the nutrient circulation through the large mass of roots.
In addition to NFT, various systems were introduced for strawberry at a limited scale, including 1) aeroponic system in which roots are hanging in the air with frequent spraying of nutrient solution, and 2) vertical stacking bucket system with nutrient solution trickling down from the top container to the bottom. It is recommended that growers test these production systems at a small experimental scale first to assure the benchmark productivity.
Vertically stacking bucket system or tower system is visually attractive, and for that reason, we have seen them used in you-pick operations. However, it is more challenging to obtain uniform growth and fruit yield for strawberry, as plants in the lower buckets do not receive enough light due to the shading by neighboring systems, while plants in the upper buckets may receive over-saturating light intensity. One solution may be increasing the spacing between towers but that may defeat the original purpose of high density production. The differences in light intensity and the resulting strawberry fruit yield between upper and lower layers of vertical growing system was reported by Takeda (1999).
Takeda, F. 1999. Out-of-season strawberry greenhouse production in soilless substrate. Advances in Strawberry Research 18:4-15.
Van Delm, T., P. Melis, K. Stoffels, M. Vervoort, D. Vermeiren, and W. Baets. 2016. Historial milestones, current methods, and strategies resulting in year-round strawberry production in Belgium. Intl. J. Fruit Sci. 16:118-128.