Leafy Greens is a partnership that recently purchased a greenhouse facility from RBI in Waterloo, Nebraska. This greenhouse was designed for the hydroponic production of green onions, but is outfitted to grow a multitude of different crops. This 8,316 sqft poly arch house has roof vents that swing open on the windward and leeward sides for flexibility in the owners passive venting operations. The walls of the production zone, easily identifiable by the more transparent glazing, have roll up curtains tucked within the side purlins to increase light transmission through the sidewall while not employed.
This facility, although relatively small when compared to most commercial ranges, employs a relatively sophisticated recycling ebb & flow water system design. This system conserves a tremendous amount of water when compared with field grown or even drain-to-waste systems. This design also minimizes fertilizer runoff that might escape the greenhouse and contaminate local water resources. This closed recycling water system maintains the irrigation water by continually monitoring the conductivity of the electrolyte solution. Water samples are scheduled to being taken during operation to understand what elements the plants are taking out of the solution and to modify nutrient recipes accordingly. This will be important since there is limited data on the holistic nutritional needs of green onions; a necessity for optimal hydroponic production. Therefore, initial operation will be an ongoing experiment for these growers and I wish them the best of luck.
The palletized unit pictured below is responsible for the water treatment in this facility. This unit was specified by RBI and designed in accordance with Hortimax. It includes a control box for housing your I/O’s, a pump set to move the fluids to their desired location, a mixing tank for ensuring homogeneity of the solution, a filter to minimize system maintenance, both an EC & Ph feedback sensors for the controller, and three venturi driven dosing, or injection, channels. These dosing channels are for two unique fertilizer solutions and one acid injector for the neutralization process. Each primary component on this rig is designed, sized, and installed together on a pallet like platform that makes the easaes the installation process.
Ebb & Flow for Beginners
This hydroponic technique is vastly used in a number of floriculture and hydroponic applications. This is because it is a growing technique that is tried and tested for variety of horticultural applications. As you can see from the simplified graphic below, water “Flows” into and fills these shallow trays when the irrigation pump is on. This water is then absorbed into the growing media enabling the nutrients to be up taken during and in between irrigation cycles. The water that has been sitting in these trays then “Ebb’s”, or drains, into a reservoir preventing the roots from being completed submerged in the solution for an extended length of time. This is because exposure to oxygen is important to the root system.
Pictured below was taken during testing and exhibits the flooded nature of the tables. The solution will rest on these tables until the timing delay in the software elapses and the associated drain valve returns to its open position. Once this has occurred, gravity will return the solution to an underground reservoir where it will remain insulated from the heat until it is demanded. It will then be pumped up, filtered, neutralized, EC corrected, and directed via control valves to its associated flood zone. For this facility 8 zones were selected to keep the pump and associated mechanics down in size.