Subsurface drip irrigation : design and installation of SDI systems in North Carolina

Distributed in furtherance of the acts of Congress of May 8 and June 30, 1 91 4. North Carolina State University and North Carolina A&T State Uni¬ versity commit themselves to positive action to secure equal opportunity regard¬ less of race, color, creed, national origin, religion, sex, age, veteran status, or disability. In addition, the two Universities welcome all persons without regard to sexual orientation. North Carolina State University, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating. NC Design and Installation of SDI Systems in North Carolina As a part of the humid Southeast, North Carolina’s climate, topography, soils, crop¬ ping systems, and water sources require special consideration when considering and implementing a subsurface drip irrigation (SDI) system. This publication is not a step- by-step design manual, but it will help you in the design process of an SDI system appro¬ priate to North Carolina. Irregularly shaped fields commonly found in humid areas can result in a system layout that differs greatly from the “normal" layout found in the SDI system in an arid or semi- arid area. Installation is best done when the soil moisture is within an optimal range, which may seriously limit the time when a system may be installed in North Carolina. And fewer systems have been installed in hu¬ mid regions, so fewer professional installers and less installation equipment are available. This publication presents both design and in¬ stallation considerations to help the grower in a humid area who is considering a SDI sys¬ tem. Topics include design criteria; pumps; filtration; chemical injection; valves; main and submain (header), dripline, and flushing manifold design; instrumentation and control systems; design implementation; installation tips; and locating an installer. Introduction Subsurface drip irrigation (SDI) is similar to surface drip irrigation, but it has driplines that are buried beneath the surface. Some drip systems have lines that are buried up to eight inches deep, but are retrieved annually and are thus very similar to surface drip systems. This publication focuses on SDI systems with lines that are permanently installed below tillage depth (Camp and Lamm, 2003). Although SDI has many important benefits State University A&T State University COOPERATIVE EXTENSION Empowering People ■ Providing Solutions for modern crop production, many challenges also exist. SDI systems must be carefully designed and installed so that they operate with proper efficiency, and so that fertilizers and chemicals can be applied in a legal, uniform, and efficient manner. SDI systems are expensive and should be designed and installed to ensure a cost-efficient system. Significant amounts of technical skill and management are required to properly oper¬ ate the systems so that peak efficiency and benefits are realized. This means that trained personnel should be involved with the design, installation, and operation of the system. Proper training and management skills are very important to the success of any irrigation operation, and this is especially true with SDI systems in which driplines are buried. While SDI systems have been used successfully for many years in arid and semi-arid locations, the topography, soils, crops, cultural systems, and climate in North Carolina and other humid regions may require a different design and installation. Before the design of an SDI system is done, determine if the intended site is suitable for SDI. Do you have an adequate water sup¬ ply, acceptable water quality, and appropriate topography for an SDI system? Design Criteria Begin by collecting information needed for a successful design. This information is referred to as design criteria. For an SDI system, these criteria will include information on climate, crops, soils, and water quality, along with system management and operational consid¬ erations. Water Requirements The SDI system must deliver the required amount of water to the crop at the time it is needed. This is called the “crop water require¬ ment. "You will need to supply the “peak” wa¬ ter requirement, or the amount of water that a crop uses during its highest water use period. During this period of peak water use, your SDI system must deliver that amount of water.