Today’s growers’ face increased pressure to find cost saving methods in every facet of their production of plant materials. The growers then turn to dealers and manufacturers to come up with new products to save time, energy, labor, or raw materials to stretch their budgets and help with profitability. Modern irrigation techniques can reduce the costs not only of water, but also labor, energy, and pesticides, as well as significantly impact revenues by improving plant quality.
One area of concern is irrigation for mums, poinsettias, and other small potted plants that are being produced in large sections or plots. Sometimes the pots are indoors but mostly these are in long rows in large open fields outside.
The benefit of drip / micro irrigation on flowering potted plants is well known in the industry. NETAFIM USA has produced quality, high value products for the agriculture, greenhouse and nursery industries for over 25 years. Traditionally, these long rows of pots have been irrigated using low flow Multi-Outlet Dripper (MOD) assemblies that have 4 or 8 individual tubes with one going to each individual pot. This method is a proven winner since each pot gets the same amount of water delivered slowly to each pot near the roots. Now, there is a growing use of ThinWall Dripperlines (TWD) or “tapes” for these systems. Both methods work extremely well, but with somewhat different benefits in layout and flexibility. This article will give you the tools to determine which method is best for you. Of course, both methods result in huge labor cost savings by eliminating the hours of hand watering.
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Multi-Outlet Dripper
• Pressure compensation – the dripper and stake will provide each plant with the same amount of water without concern for elevation changes. Each dripper offers uniformity of approximately 94% to each pot even with long rows of pots since the polyethylene tubing can be sized according to the length and flow required.
• Water savings – the check valve feature on the dripper prevents the line from draining after each irrigation cycle. This is especially important when there are low spots in the fields or a constant slope. Without this feature, the lowest pots can become overwatered by the drainage from the supply pipes.
• Design flexibility – the distance between pots and/or rows can vary and the delivery of the water is the same.
• Initial cost – approximately 50 cents per pot* for the one time purchase of this system. The initial cost of this system will be offset over the life of the system since no additional purchases will be needed in each succeeding year of operation.
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• Portability and reuse – designed for use year after year. The MOD assembly is removed from the dripper which is installed in the poly tubing at the end of the year and placed into boxes for storage or transport. The dripper supply tubing with the dripper still attached is rolled up and stored separately.
• Flow requirement – Each plant gets either 0.25 or 0.50 gallons per hour (gph), depending on product selection, which means a 15 gallon per minute (GPM) water source can water 1800 to 3600 pots.
• Filtration requirement – 120 mesh.
• Pressure requirement – 20 psi to 35 psi depending on length of rows. The drippers operate with a consistent flow between 10 and 45 psi.
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Thin Wall Dripper
• Initial cost – With pots spaced every two feet, the price per pot* is approximately 7-8 cents. Since the cost is so low per plant, it is recommended that the highest quality TWD be used to assure reliability throughout the season and uniformity in the delivery of water to each pot. The TWD is typically disposed of at the end of each season.
• Non-pressure compensating – Best suited for short runs of approximately 150’ or less. Some TWD is available in PC although this has not yet seen widespread adoption.
• Spacing and layout – the TWD can be ordered with any spacing between each dripper. Once the TWD is laid out for each row, the pots are then lined up under the individual dripper. Often a stake or wire will be placed over the TWD and into a pot every so often to keep the TWD from being blown off the pot during rains or windy days.
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• Simple installation - Installation is best in the early morning to minimize the effect of expansion and contraction of the TWD during the day and night. Many installation methods are available to minimize the movement of the TWD. (See pictures) Some growers have used “bungee cords” attached to a fitting at the end of the line to allow for this expansion and contraction. Others have simply nailed the folded-over ends of the TWD to a board, which is stationary on the ground. Others have used a combination of both methods by nailing the TWD to a board or taping it to a pipe and then attaching the “bungee cords” at a few places to the board or pipe.
• Dripper up or down – normally the TWD will lay on the top of the pot, with the dripper opening facing down. This will let the water drip directly into the pot. However, with elevation changes the water could flow down the tube. The pot edge will normally catch the water and keep it in the pot. With good filtration, the dripper should not experience any clogging from debris. Some manufacturer’s “tape” is susceptible to clogging when in this position. Netafim USA’s TWD is specially designed to work under harsher conditions.
• Flow requirement – a standard dripper of 0.4 gph is normally used. For 150’, the gpm per row with a pot every 2’ would be approximately ˝ GPM. A 15 GPM water source could water approximately 2200 plants per zone.
• Filtration requirement – 120 mesh.
• Pressure requirement – 12 psi for 8 mil TWD.
Another aspect of these systems is the ability to deliver fertilizers and chemicals at a uniform rate to the plants. Since water and nutrients are delivered directly to the soil media and the root zone, losses are minimized compared to overhead watering methods. Also, pesticides applied to foliage will not be washed off from daily watering. Finally, water on foliage and flowers can spread disease.
Some general installation tips:
Debris can be a big headache if it is allowed to get into the system and travel to the drippers. To avoid this, remove all burs and shavings resulting from cutting and solvent cementing the PVC and flush the mainline piping. Then, connect the controls, filters, pressure regulators and sub-mains. Do another flush to eliminate any new debris. Finally, connect the poly tubing or TWD, but leave the ends open. Do another flush and close the ends to allow the system to pressurize. Check for any connections that are not secure and correct any found. Do an inspection of the system regularly to check for proper operation.
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