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ARS Home » Southeast Area » Florence, South Carolina » Coastal Plain Soil, Water and Plant Conservation Research » Research » Publications at this Location » Publication #85979


item Camp Jr, Carl
item Sadler, Edward

Submitted to: Irrigation Associations Exposition and Technical Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 10/17/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: The site-specific application of irrigation water and fertilizer should offer opportunities to conserve water, to reduce the chance of either drought or flooding stress, and to reduce leaching of fertilizer or pesticides below the field in the areas subject to such losses. A center pivot irrigation system was modified to permit a range of water and chemical application rates to areas about the size of a 2-car garage. The water application system consisted of multiple segments 30 ft long, each with three manifolds. Each manifold was controlled separately, allowing up to eight separate water application depths for any given speed of the system. The system is controlled by a computer using specialized software and soil, crop, and cultural information stored in a database. While the modified irrigation system was being developed and improved, it was used to apply water and nitrogen to a corn-soybean field experiment with regular plot boundaries during 1995-97. Initial measurements of water and N-fertilizer applications show acceptable uniformity. The irrigation control system was improved, and its reliability was increased during this experiment. A second center pivot system is being modified to provide variable-rate applications of water, nutrients, and pesticides to areas with irregular boundaries, which are typical of Coastal Plain soils.

Technical Abstract: Research suggests that spatial yield variability for the southeastern Coastal Plain may be caused primarily by water relations. This causes difficulties in scheduling irrigation for conventional center pivot systems. Thus, we designed and constructed a site-specific center pivot irrigation system that could independently apply variable amounts of water and chemicals to 900-sq-ft areas within the irrigation system. A commercial center pivot system was modified by adding three 30-ft manifolds in each of 13 segments along the truss. Manifolds and nozzles were sized to provide eight depths, 0 to 0.5 in. in 0.07-in. increments, when traveling at half speed. A computer-controlled management system obtained the position from the center pivot controller and switched the appropriate valves to obtain the application rate desired. During 1995-97, ,the system was used for water and N-fertilizer applications in a fixed-boundary field experiment. Initial observations and measurements of water and N-fertilizer application uniformities were acceptable. A second center pivot system is being modified for site-specific water, nutrient, and pesticide management on a field with soil variation (irregular boundaries) typical of the Coastal Plain.