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Flood Floors & Irrigation

How small can you go?
Grower Talks Magazine Technology Report


Should a Grower even consider Flood Floors in a single Quonset house?
Or in a couple bays of gutter-connected houses? Maybe!

So far mostly larger operations have installed Flood Floors. The reason was not necessarily high initial costs, but the lack of experience with such systems. With little support available, it took a good measure of pioneering spirit and resources to do the jump. This has changed now. Small and medium size growers discover that they can have the same benefits larger ones do: saving labor, uniform watering, dry foliage for reduced disease problems, flexible use of the growing space, low maintenance, full water recirculation.

The Technical Side

There is no limit to how small and simple Flood Floors can be. A tree nursery in Oregon fills a plastic lined 100 square foot section of greenhouse floor with a garden house. Different size Flood Floor systems call for different designs. Simply scaling down a large system will make it expensive and often impractical.

In a Nutshell: With proper design, the quality of watering, re-circulation and basic automation can be maintained even in small systems.

Some features are common to Flood Floors of any size:

• The plants sit on concrete floors, which are pitched just enough to ensure puddle-free drainage.
• Curbs or special rubber barriers separate the floor area into manageable watering zones, which generally correspond with the bays of the greenhouse.
• Each watering zone is filled 1 - 2 inches deep with water, and drained again. The plants sit in the water for less than 10 minutes. This is time enough for the capillary action to provide a thorough watering, but not long enough to allow pathogens to migrate into the surrounding water.
• Floor heat is crucial for the optimum microclimate and provides valuable control of the root temperatures. Larger floor heat systems typically tie in with the overhead heat. Small systems can be as simple as a small boiler and a circulation pump connected to the in-floor tubing.

Other features vary with the size and application of a system. A system of 10,000 square feet or more typically has:

• 10 — 100 watering zones of 1000 — 6000 square feet each
• Short watering times of an hour or less per acre
• Two or three solution storage tanks that allow the grower to choose between fertilizer mixes or plain water
• Low maintenance water filtration
• Fully automated operation, often integrated with an environmental computer.

As the systems get smaller, the picture changes.

• The number and size of watering zones decreases. More and smaller zones add flexibility, but cost marginally more to install than fewer large ones.
• There is less need to push for high speed. Even a 'slower' system will water every thing in less than an hour. However, we still want to be sure the water does not sit for more than 10 minutes on any watering zone.
• Experience shows that a choice of one or two fertilizer solutions covers the needs of most small growers. With appropriate design it is easy to add more tanks later if needed. The higher costs for in-ground tanks are usually justified in larger systems; the smaller ones typically have above ground tanks for ease of installation. The size of the tanks is largely determined by the size of the watering zones, and not much by the number of zones in a system.
• Even the smallest systems normally run unattended on a programmable irrigation controller.

It's the Economy

No matter what the size of a Flood Floor system, the initial investment is considerable. Realistically we look at $ 4.50 - 6.00 per square foot. Now don't stop reading yet! These numbers include all materials and all (often hidden) labor costs from design to operating system. And it buys more than a labor saving irrigation system: concrete floors for flexibility and sanitation, floor heat for better growth and disease control, and a leap ahead of any environmental regulation.

Flood Floors are a long-term investment, with 10-20 years of low maintenance operation to be expected. For many smaller growers such up-front investment is out of reach, even if it pays back handsomely. That's where another aspect of Flood Floors comes in: practically all technology involved is simple. A grower with some handyman-skills can do almost all the work himself and with his crew. And not all work needs to be done at once. It is common to put the piping into the ground, pour the floors in increments, and add tanks, pumps and controls as the situation allows. Well draining concrete floors are an asset even before the flooding is operational.

Where Flood Floors of any size may not be a good investment:

Inexpensive greenhouse space that is used only seasonally for bedding plants is not a likely candidate. While many bedding crops do well on sub-irrigation, it is really the potted crops where the payoff comes in. Flood Floors can easily be installed in existing greenhouses, but if they are likely to outlast the structure, they can turn into a liability.

Ebb and Flood Bench systems are helpful where manual work on the crops is required. However, cost, high maintenance and labor-intensive handling on fixed and rolling benches make the floor option attractive for many growers.

Going for the Floors

Flood Floors are essentially simple. But well functioning simplicity is the result of competent design and lots of experience. Connect with growers who have built and operate Flood Floors. Talk to professionals about the many options to tailor a system to your specific needs, and prevent unnecessary expenses. 60 - 70% of the cost of Flood Floors lie in the concrete work. Sophisticated concrete placing and finishing equipment can be helpful, but is not essential for good floors; experienced and careful people are. Laser leveling is indispensable.