Submitted to: Applied Engineering in Agriculture
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/19/2005
Publication Date: 2/23/2006
Citation: Stone, K.C., Sadler, E.J., Millen, J.A., Evans, D.E., Camp, C.R. 2006. Water flow rates from a site-specific irrigation system. Applied Engineering in Agriculture. 22(1):73-78. Interpretive Summary: Irrigation of agricultural crops is essential to profitable production in many locations. Traditional irrigation systems apply water at the same rate over an entire field. In fields with numerous different soils, this could result in some areas being over irrigated and other areas being under irrigated. New technology now enables site-specific management of irrigation systems. The site-specific irrigation allows precise amounts of water to be applied to specific areas where and when plants need them for optimal growth. A Site-Specific Center Pivot Irrigation Facility was built in Florence, SC, to study the management and operation of site-specific irrigation systems. This system has been in operation since 1995. To evaluate how the system has operated and verify how well it delivers water to each irrigated plot, we conducted an experiment to exhaustively measure the flow rates from the site-specific irrigation system. The irrigation system could apply different water rates in 30-foot distances along its entire length. We tested each of these 30-foot distances. We found that the irrigation system was delivering water to each 30-foot section at rates approximately as it was designed. Only a few of these sections applied water significantly above or below the designed amount. This provides us with information needed to properly interpret results from crops grown under the irrigation system.
Technical Abstract: Site-specific irrigation is defined as delivering precise quantities of water to specific areas in irrigated fields. Since the 1990's, site-specific irrigation research has been expanded to include the precise delivery of water and nutrients to these specific areas based on soil type, soil moisture status, crop needs, and other user defined objectives. A site-specific center pivot irrigation system was designed and installed in a field with highly variable soils of the US eastern coastal plain. The system consisted of 13 segments (or rings) along the length of the center pivot with three delivery manifolds in each segment. The system was designed to apply approximately 12.5 mm of water in any selected ring when operated at 50% travel velocity. Quantifying the amount of water from the site-specific irrigation system is essential to documenting the system's performance and interpreting experimental results. We developed a measurement system to evaluate the water delivery of the irrigation system. We compared the measured water delivery from each segment of the site-specific irrigation system to the design parameters. We found that the irrigation system was delivering water to the control areas at rates approximately as it was designed. A total of 77 ring and manifold combinations were tested. Of these 77 combinations, we found that 8 had flow rates greater than 10% different from the design flows. The manifolds with the lower flow rates typically were more likely to be significantly different from the design values. This was most likely related to potential clogging of the low flow nozzles that have smaller orifices. When the manifolds were used in combination, they compensated for each other and produced application depths that were fairly uniform to the designed data.