Design and Components of an OHS/APS System

    The basic components of an OHS system are as follows:

  • Drip irrigation system
  • Self-priming pumps
  • Electric power (diesel power is possible, but more complicated)
  • Automated fertilizer injection
  • A minimum of two fertilizer supply tanks
  • Control systems capable of full automation of valve operations, and proportionate metering of fertilizer
  • Capability to apply the proper amount of water to meet the needs of the trees during the available daily pulse period.

    Proper design of an Open Field Hydroponics (OHS) system is critical.  The system must be capable of supplying water and
    nutrients in a very exacting manner.  Fully automated zone controls and fertilizer injection is essential.

    OHS theoretically includes the irrigation and fertilizer application technology, and OHS systems can certainly be used in classical
    grove designs.  However, Arapaho recommends adoption of a Advanced Production Systems (APS) approach layered over the
    OHS core technology.

    The Advanced Production Systems approach includes the following:

  • High density plantings - 250 to 400 trees per acre
  • Aggressive Psyllid control to reduce tree losses to Greening
  • Plant growth, flowering and fruit set management to achieve early production
  • Intensive pruning practices designed to maintain dense tree canopy

    Together, OHS and APS will allow Florida citrus growers to achieve high yields early in the life of a new grove.  South Africans
    have also proven that APS is the most effective way to achieve long-term effective management of Greening.

    OHS/APS Costs:

    The systems cost about 20% more per acre than microjets, and of course there is a higher tree cost per acre due to the number
    of trees.  However, the cost per tree is much less than conventional planting systems.  This is the driving factor behind the
    economic performance.  The establishment and operating cost is much less per tree, and therefore per box, until the trees form
    a solid hedgerow.  Since this occurs earlier in the life of the grove, operating profits are much higher over a 10-year period.  We
    have developed a  cost-comparison model for you to use when evaluating different planting schemes..

    We are finding that production costs in the first few years are much lower per-acre than conventional microjet blocks, and only
    about half the per-tree cost of conventional.  In later years, production costs may be higher due to the requirement of hand labor
    for pruning.  The pruning is a combination of hand and machine as opposed to all mechanical as we now use in Florida.  Other
    operations, such as girdling, may require more hand labor as well.  On the other hand, savings will be achieved due to
    elimination of broadcast fertilizer applications, reduced herbicide costs since water and fertilizer are applied only to small
    surface areas and the trees will begin shading in the row sooner, and irrigation operation as result of hands-off automation and
    less maintenance of emitters and lines.

    See for yourself -- Download Arapaho's Cost Comparison Model Here
Below - 4 year old OHS Lemon Planting near Nelspruit, South Africa.  This planting produced 500 boxes per acre of seedless
lemons 36 months after planting.  Greening is present in the grove, but tree losses have been minimal due to psyllid control with
imidacloprid injected into the drip system.
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