Author
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Camp Jr, Carl |
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Sadler, Edward |
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Submitted to: Irrigation Journal
Publication Type: Popular Publication Publication Acceptance Date: 2/13/1997 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: Spatial crop yields, since 1985 at Florence, SC, show little correlation with expected yields for soil map units. However, areas of higher and lower yields in corn persist from year to year, even in drought years. This suggests that, for the SE Coastal Plain, a primary cause of spatial variability is poor water relations. Irrigation would normally be used to supplement rainfall, but soil variability interferes with scheduling irrigation for center pivots. To solve this problem, we designed and constructed a site-specific center pivot irrigation system that could apply different rates of water and chemicals to each 100-sq-m area. A center pivot was modified by adding three 9.1-m manifolds in 13 segments along the truss. Nozzles were spaced 1.5 m apart, and both manifolds and nozzles were sized in 1x, 2x, and 4x multiples. At half speed, all combinations of the three manifolds provided up to 7x the minimum rate, totaling 12.5 mm in 1.8-mm increments. A programmable, computer-controlled management system was installed on the movable part of the center pivot system. This controller obtained the position from the center pivot controller via a radio and switched on valves to obtain the application rate for each specific area. During 1995 and 1996, the system was tested on a field experiment. Using these experiences, a second center pivot will be modified for site-specific water, nutrient, and pesticide management on irregular-shaped areas typical of a Coastal Plain field. |
