Greenhouse Production Systems
Substrate Culture Systems
Floor Culture System
Floor culture systems are one of the most efficient and cost-effective methods of soilless culture, which involves replacing the soil with a media, typically sand, in the greenhouse (See Figure 14.12). Floor culture systems have been successful used for vegetable production in greenhouses and is considered a good means of providing plants with a uniform, well-drained rooting medium. The principal crops grown in sand culture systems are tomatoes and cucumbers. Sand culture systems for greenhouse crops (e.g., tomatoes or cucumbers) are typically irrigated and fertilized by drip emitters. Perforated (ooze) hose is installed more easily but is not as durable (it must be replaced between crops). As with other open irrigation systems, the nutrient solution is applied to the upper surface of the substrate, and any excess solution applied is allowed to drain from the substrate out to the environment.
Advantages and Disadvantages
Floor culture systems have many advantages over other substrate systems. The fact that it is an “open” irrigation system, whereby the nutrient solution is not recycled, greatly reduces the likelihood of diseases such as Fusarium and Verticillium spreading in the medium. Another advantage is the excellent capillary action of sand, which results in lateral movement of nutrients so that there is an even distribution of nutrients throughout the root zone. Practical advantages of sand culture include lower construction costs, simplicity of operation, and easy maintenance and service.
Bed Construction
Assuming the greenhouse has concrete footers, the soil is first removed to a depth of 12 to 16 inches (30 to 40 cm) before lining the excavated area in the greenhouse. The footing refers to the point at which the greenhouse structure meets the soil where structure rests upon. The floor should have a slight grade of 6 inches. (15 cm) per 100 feet (30.5 m), so that the area may be drained or leached when necessary. Generally, two layers of 6-mil plastic are used to cover the entire floor. Before installing the polyethylene, the floor should be graded· and packed. Polyethylene sheets should be overlapped several feet (0.6 m) when more than one sheet is required in wide greenhouses.
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