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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 #73110


item Camp Jr, Carl
item Sadler, Edward

Submitted to: American Society of Agricultural Engineers Meetings Papers
Publication Type: Proceedings
Publication Acceptance Date: 7/15/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Patches of sandy or clayey soils can cause big differences in crop yield from area to area in the same field. These differences are the reason for current interest in site-specific crop management, in which fertilizer, pesticides, plant population, or irrigation is customized for the soil at a specific place in the field rather than applied uniformly over the entire field. Most development in the site-specific farming area has been for spreading fertilizer. The site-specific application of irrigation water 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 water application system consisting of multiple segments 9.15 m long was developed and attached to a commercial center pivot irrigation system. Each segment includes three manifolds attached to the main truss system. Each manifold is controlled separately, allowing up to eight separate water application depths for any given speed of the system. The smallest controllable area is about 10 m on a side, making more than 500 controllable plots under the 5.9-ha system. Soil, crop, and cultural information stored in a database will allow computer control of the system. The modified application system was installed on a commercial center pivot system and used to apply water and nitrogen to a field experiment in 1995.

Technical Abstract: Soils in the southeastern Coastal Plain are predominantly coarse-textured and are also extremely variable with respect to properties that affect crop growth, often within the area of a small center pivot irrigation system. Large differences in soil properties over small distances severely complicate water and nutrient management because the entire system area must be managed uniformly for most commercial irrigation systems, especially center pivot and linear systems. The objective of this research was to develop a multiple-segment water and nutrient application system for a center pivot irrigation system to allow variable application rates within small areas of the system at a given speed of travel. Each segment is 9.15 m long and consists of three manifolds sized to provide 1x, 2x, and 4x rates, where x is a minimum application depth. The three manifolds are operated either individually or in various combinations to provide eight application depths (0-7x) at a given travel velocity. Water application depths vary from 0 to 12.4 mm when the outer tower is moving at 50% of full speed. Water is delivered via industrial, full-cone and wide-angle spray nozzles that were selected to provide the desired range of application depths for the entire pivot length. The variable-rate application system was installed on a three-tower, commercial center pivot system and used to apply water and nitrogen to a field experiment in 1995.