Greenhouse Production Systems
Substrate Culture
Ebb-and-Flow System
Ebb-and-flow benches (also called ebb-and-flood benches) combine an elevated benching system with a closed subirrigation system (Figure 15.7). It provides for individual watering and fertigation of a number of different plants on different spacing without individual feed lines going to each plant and without overhead watering. Commercial ebb-and-flow systems are used chiefly for plants that are on the production tables for a relatively short period of time, such as seedlings and the production of potted plants in the floriculture industry.
Advantages and Disadvantages
The ebb-and-flow system is one of the simplest hydroponic systems to set up and use, but it still takes some experience and effort to master. The ebb-and-flow system costs are usually very low in comparison to many other substrate systems because it doesn't require any high-tech, expensive components. The ebb-and-flow system is well-used because it can use many different types of growing media, such as expanded clay pellets, perlite, sphagnum moss, and rockwool.
Benches
Ebb-and-flow benches may be designed as stationary benches or as rolling benches, like Dutch trays. Either approach can work just fine, so the choice depends largely on personal preference and the desire to automate other production practices. The primary characteristic of an ebb-and-flow bench is the tray that makes up the bench surface. The tray may be made of hardened plastic or aluminum. The length and width of the tray vary depending upon the desired bench dimensions.
Irrigation Method
At one end of the tray, there is an inlet and an outlet. The inlet allows fertilizer solution (or water) to be pumped into the tray. As fertilizer solution is pumped into the tray, it first floods the deepest of the channels. When the deepest channels are flooded, the solution floods the next level of channels. After both sets of channels are flooded, the solution continues to rise above the bottom surface of the bench. In a production situation, containers with plants would be placed on the tray surface.
Dutch Trays
Dutch trays are placed on steel tracks that serve to not only support the trays, but the trays (which have small wheel-like structures underneath) roll on the metal support structure. This allows trays to be rolled together to maximize space usage efficiency, but the track system also serves as a transportation system around the greenhouse facility. When the plant material needs to be moved to another location in the facility, the trays may be rolled on the steel tracks to a major aisle or walkway.
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