Session 23. Products and Developments in Microirrigation
Use and Performance of Thermoplastics in Microirrigation Systems
Elaine Marans
Microirrigation applications require that system components be manufactured from suitable materials that will perform consistently over the lifetime of the installation. Manufacturing processes and harsh field conditions require the materials used to have outstanding properties. Requirements may include heat and hot water resistance, mechanical strength, resistance to chemical attack, creep resistance, UV stability, dimensional stability, impact and flexural strength, ease of processing, and economic feasibility. Thermoplastics are widely used in fluid engineering applications such as microirrigation, as they provide a partial solution to these stringent requirements. System components such as emitters, valves, fittings, filters, hose, pipe, and controller housings are molded or extruded from a variety of thermoplastics, such as ABS, acetal, nylon, polyester, polyolefins, and PVC. These materials have at lease one property that imposes limitations on either the end use of the product or the manufacturing process. Selecting the most suitable material for each component part involves a trade-off between processability and various performance criteria. Material selection and component end use would be enhanced by improving communication between plastic suppliers, component manufactures and agricultural customers.
Keywords: Microirrigation, Irrigation equipment, Plastic
Abstract taken from paper found on pages 675 to 681 in Proceedings of 5th International Microirrigation Congress, April 2-6, 1995, Orlando, Florida. American Society of Agricultural Engineers, 2950 Niles Road, St. Joseph, Michigan 49085-9659, USA. Phone: 616-429-0300 FAX: 616-429-3852 EMAIL: HQ@ASAE.ORG
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Single Swap-Top Spray Jet Does the Job of Three
Susan S. Thayer
The number one choice of spray jets for microirrigation of citrus and other trees has long been the 360o x 14 stream (or spoke) pattern. This full-circle stream jet, which provides complete feeder-root coverage with minimal waste of water or chemicals, is an excellent choice for mature-tree irrigation. However, this jet is not the most efficient choice for young trees or for frost and freeze protection. For these situations, the very fine mist of the fan pattern spray jet has proven itself far superior. The Maxijet Swap-Top (used in conjunction with the Max-One Fan or Max-Cone Down Spray) was developed to give growers the best of both worlds: a single jet assembly that provides both a stream pattern for irrigation and a fan pattern for frost/freeze protection or young-tree irrigation. The Swap-Top series of color-coded jets is designed with one jet style on top and another on the bottom so growers simply slide off the Swap-Top, flip it over and slide it back again to switch patterns. The Swap-Top has proven itself to reduce labor, reduce costs and increase profitability in a wide range of growing operations including citrus, ornamental, land-scape, nursery, and commercial irrigation.
Keywords: Microirrigation, spray jets, frost/freeze protection, innovations, trees
Abstract taken from paper found on pages 682 to 687 in Proceedings of 5th International Microirrigation Congress, April 2-6, 1995, Orlando, Florida. American Society of Agricultural Engineers, 2950 Niles Road, St. Joseph, Michigan 49085-9659, USA. Phone: 616-429-0300 FAX: 616-429-3852 EMAIL: HQ@ASAE.ORG
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Enhancing Subsurface Drip Irrigation Through Vector FlowTM
Douglas F. Welsh, Ph.D., Urs P. Kreuter, Ph.D., & Joe D. Byles
Water conservation has become a critical issue within the irrigation industry over the past several years. A leading technology in the search for increased irrigation efficiency and water conservation is subsurface drip irrigation.
Over the past decade, subsurface drip irrigation has become a viable water saving technology in agriculture. Transfer of this technology into landscape applications has, however, been troubled by questionable results. Non-uniformity of water application has been of particular concern. Poor horizontal movement of water delivered by subsurface drip irrigation frequently produces intermittent yellowing in turf grasses which has led to reduced spacing of drip lines and thus increased installation costs.
A new technique of manipulating the wetting pattern of subsurface drip irrigation is now available. It is based on the use of an impermeable membrane to transform the point sources of water in drip lines to a broad-band source from which capillarity operates to draw water upward and outward. This technology, called Vector FlowTM, thus incorporates the relative uniformity of broadcast irrigation and reduced evaporative losses associated with subsurface drip systems. Theoretical discussions and field observations for the new technology are presented.
Keywords: Capillarity, drip irrigation, landscape irrigation, subsurface irrigation, trickle irrigation, turf irrigation, water conservation, wetting pattern
Abstract taken from paper found on pages 688 to 693 in Proceedings of 5th International Microirrigation Congress, April 2-6, 1995, Orlando, Florida. American Society of Agricultural Engineers, 2950 Niles Road, St. Joseph, Michigan 49085-9659, USA. Phone: 616-429-0300 FAX: 616-429-3852 EMAIL: HQ@ASAE.ORG
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Microirrigation and Water Consumption in a Rain-Shielding Vinyl Film Greenhouse
Yoshisuki Nakano and Masaharu Kuroda
About 40% of vegetables in Japan are produced in greenhouse culture. The total area of greenhouse was about 58,000 ha in 1991 and the area is still increasing. One of the reasons for the increasing number of greenhouses derives from climatological characteristic in Japan. Under the condition of high rainfall amounts to 1800 mm/year, keeping soil moisture conditions suitable for crop growing is sometimes a very big problem. From technical point of view, irrigation is easier than drainage for controlling soil moisture. According to this situation, the demands for microirrigation systems are increasing with the development of the greenhouse culture. We briefly introduced characteristic features of rain shielding greenhouses.
When irrigated by point or line source irrigation methods, partial wetting fronts are formed on the soil surface. The evaporation from these small wetted portions cannot be treated as one-dimensional. We discussed a method to estimate soil surface evaporation and crop transpiration from partially irrigated field.
Keywords: Greenhouse, Evapotranspiration, Convection, Partial Wetting
Abstract taken from paper found on pages 694 to 700 in Proceedings of 5th International Microirrigation Congress, April 2-6, 1995, Orlando, Florida. American Society of Agricultural Engineers, 2950 Niles Road, St. Joseph, Michigan 49085-9659, USA. Phone: 616-429-0300 FAX: 616-429-3852 EMAIL: HQ@ASAE.ORG
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Considerations for Component Selection in Microsprinkler Systems
Brian J. Boman and Marion L. Parsons
Microsprinkler irrigation is by far the most popular irrigation method for citrus in Florida. Field installations typically employ 38-70 L h-1 (10-20 gph) emitters on stake assemblies with 0.6-0.9 m (2-3 ft)lengths of 4-mm spaghetti tubing. Spray emitters usually have slotted caps or deflector plates which typically distribute water in distinct streams. Spinners use a moving part which rotates to disperse the water stream over the wetted diameter. Both types of microsprinklers are often preferred over drip systems since they provide significant freeze protection for young trees and have a larger diameter wetting pattern, which is especially desirable in areas with coarse textured soils where lateral movement of soil water is limited. Over the last few years, the authors have conducted several studies to determine appropriate components and operational criteria for microsprinkler systems in Florida citrus. This paper briefly summarizes several of these studies which relate to application uniformity, clogging, insect problems, wear, and wetting patterns.
Keywords: Microirrigation, emitters, citrus, microsprinkler assemblies
Abstract taken from paper found on pages 701 to 707 in Proceedings of 5th International Microirrigation Congress, April 2-6, 1995, Orlando, Florida. American Society of Agricultural Engineers, 2950 Niles Road, St. Joseph, Michigan 49085-9659, USA. Phone: 616-429-0300 FAX: 616-429-3852 EMAIL: HQ@ASAE.ORG
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The Design of Trickle Irrigation Systems with Microtubes as Emitters
Achi M. Ishaq and Mohamed A. Ibrahim
Proper management of irrigation water in arid and semiarid regions is important not only from the point of view of water conservation but also from the point of view of optimum crop yields. In a country like Saudi Arabia where water is scarce, trickle irrigation systems become an attractive alternative for conserving water. Usually microtubes are used as emitters in the trickle irrigation network to deliver the same amount of water throughout the network. Microtubes also have many advantages compared to other emitters. For this reason, a comprehensive method for the design of microtube trickle irrigation systems is needed. Also, a device that can be referred to in the field where computing facilities may not be readily available is needed. In the study, a chart and nomographs have been developed for the design of microtube emitters to deliver the same amount of discharge by all microtubes along the network. In the case of coiled microtubes, design chart and nomographs have been modified.
Keywords: Microtubes, Trickle Irrigation, Monographs
Abstract taken from paper found on pages 708 to 716 in Proceedings of 5th International Microirrigation Congress, April 2-6, 1995, Orlando, Florida. American Society of Agricultural Engineers, 2950 Niles Road, St. Joseph, Michigan 49085-9659, USA. Phone: 616-429-0300 FAX: 616-429-3852 EMAIL: HQ@ASAE.ORG
