Greenhouse Mechanization and Material Handling
Greenhouse Benches
Greenhouse benches provide basic convenience in the production of crops. The use of greenhouse benches has several advantages over planting directly in the greenhouse soil or setting pots on the greenhouse floor: (1) plants are at a more convenient height to work comfortably; (2) benches permit a more effective display of plants; (3) benches provide improved air circulation and environmental control around the plants; and (4) benches permit better disease and growth control.
Benching Materials
The most prevalent commercial greenhouse bench material is metal because of its durability and versatility. Construction consists of galvanized tubular steel legs and cross members topped with aluminum or steel side rails. Ideal for greenhouses, the simple design of metal benches facilitates ease of construction while providing an aesthetically pleasing display. Its lightweight construction allows ease of movement, offering flexibility in layout. Additional advantages include longevity, low maintenance, good air circulation, corrosion resistance, and passage of water and soil through the bench top. Wood benches offer the greatest array of design of any greenhouse bench, as they can be commercially produced or built by the grower.
Bench Layout and Size
Three basic layouts exist for the arrangement of benches in the greenhouse: longitudinal, peninsular, and moveable bench layout (Figure 4.1).
Bench Layout
Longitudinal layout results in the arrangement of benches in a linear fashion, with all benches and aisles running the same direction in the greenhouse. This permits long continuous runs of watering lines, heating pipes, and/or plant support techniques. Peninsular layout utilizes a large main aisle with benches running perpendicular to the main aisle, with smaller aisles between these benches. Aisle width must be kept to a minimum.
Aisle and Bench Size
Center aisles are typically 3 to 4 feet (0.9–1.2m) wide to accommodate service carts and other large pieces of equipment. In very large greenhouse operations, center aisles may be up to10 feet (3m) wide to accommodate many workers and a large volume of cart traffic. Side aisles, however, are typically 18 inches (46cm) wide, allowing only for people access to the crop. The size of the benches and width of the aisles greatly affect the amount of available growing area.
Stationary Benches
These strong, durable benches remain in one place (See Figure 3.1). The main reason to use this type of bench is to provide additional aisle space when more access to the plants is needed. Stationary benches are common in retail, educational, and research growing operations.
Container Benches
Container benches (also called movable benches, rolling benches, pallet benches, or Dutch trays) offer complete handling of plant material from planting to shipping. By using a container bench system, a grower can easily move the crops between different climate zones. Some growers move the benches in and out of coolers where plants are vernalized (given a period of cold so they’ll initiate flowers). There are two types of movable systems: moving benches and transport trays.
Ebb-and-Flood Benches
Ebb-and-flood benches typically consist of a metal frame that can be leveled with a water-tight liner or water-tight movable trays to contain the nutrient solution (See Figure 3.6). Channels in the bottom of the bench allow the water to distribute evenly and to drain rapidly when the water supply is shut off. This allows the bench top to dry reducing algae growth and disease potential. In operation nutrient solution is pumped from a holding tank to a level of ¾ to 1 inch depth in the bench and held there for 10 minutes or long enough for the media in the container to absorb the solution.
Trough Benches
Trough benches typically consist of a metal frame that supports a series of troughs running lengthwise across the bench (See Figure 3.7). The troughs are usually made of aluminum or polystyrene plastic. Unlike an ebb-and-flood bench system, which is perfectly level, trough systems arc usually sloped slightly from one end to the other.
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