Submitted to: International Conference on Water Resources Engineering Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: March 31, 1999
Publication Date: N/A
Technical Abstract: Research results indicate that spatial yield variability for the SE Coastal Plain may be caused primarily by water relations. Management of water and chemical applications is difficult with conventional irrigation systems because they apply uniform depths of water to either the total area or to relatively large areas within the system. Thus, a site-specific center pivot irrigation system was developed that could independently apply variable rates of water and chemicals to 100-m**2 areas. A commercial center pivot system was modified by adding manifolds and nozzles in 13 segments (each 10 m long) along the truss to provide eight application depths at a given tower speed for each segment. A programmable, computer-controlled management system obtained the positional data from the center pivot controller and switched the appropriate valves to obtain the application rate desired. During a four-year period, the system applied water and N fertilizer to fixed-boundary plots in a field experiment. Measured water application uniformity values within control elements were similar to design values. Primary control is based on stored data but can be augmented via dynamic measurements. The control system was modified to provide site-specific management on areas of variation with irregular boundaries typical of the Coastal Plain. Infrared thermometers mounted on the system were used for thermal mapping of soils and crops. Within the same control element, a separate pesticide system provides site-specific pesticide applications that are independent of water and nutrient applications. Unique geospatial data and productivity functions for both water and nutrients on specific soils are required to optimally manage water and chemical applications to these areas of variation.