| | With a Veris mapping cart, scientists can measure the electrical conductivity of soils, which correlates with soil texture. (Photo by Mark Claesgens) |
| | | Figure 1. Overlaying a boundary using the LSU GIS database and the SSToolbox program identifies a 78.3-acre field, called the Gin Ridge field, on the Northeast Research Station at St. Joseph. |
| | | Figure 2. Comparisons of electrical conductivity surface data (EC) and topographic elevation maps facilitate soil texture mapping, which is used to determine rate of application. |
| | | Figure 3. A grid sample overlay of the nematode population densities indicates that high or very high nematode counts were found only on the ridge areas of the field that also correspond to the lighter soil textures. |
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Eugene "Gene" Burris, Richard Costello, Boyd Padgett, Charles Overstreet and Maurice Wolcott
LSU AgCenter scientists have launched a project to explore the use of geographical information system (GIS) and global positioning system (GPS) technologies to manage nematodes that affect cotton production in Louisiana soils. GPS-based equipment makes it possible to measure soil electrical conductivity for texture mapping, to develop topographic maps and to apply variable rate treatments. Currently, nematode treatments are usually applied uniformly across fields, often resulting in considerable over-application.
The southern root-knot nematode is a severe nematode pest in Louisiana soils. Crop rotation, root-knot nematode resistant varieties and pesticides are required to manage the pest. Agronomic options of crop rotation and use of resistant varieties are usually limited. When chemical treatments are selected as a principal means of control, costs can exceed $30 per acre for high infestations of root-knot nematodes.
In 2000-2001, preliminary data were collected from the Gin Ridge field at the LSU AgCenter’s Northeast Research Station near St. Joseph, La., which was highly infested with root-knot nematode. Surveys of the Gin Ridge field included soil electrical conductivity readings measured with a Veris mapping cart (see photo this page), topography data collected using precision laser equipment and soil samples taken on a 1-acre grid. From these samples, soil texture and nematode population densities were determined. All applications incorporated a differential global positioning system to ensure accurate data collection. These data were used to segregate the field into zones characterized by differences in soil texture and to show the relationship of plant parasitic nematode populations within different soil zones.
Information collected was analyzed using SSToolbox, a computer program used with GIS technology. In Figure 1, the 78.3-acre Gin Ridge field boundary is outlined and overlaid on an aerial photo. In Figure 2, the comparisons of field zones are shown for the Veris electrical conductivity data and the elevation data. Several different soil textures occur in the 78.3-acre field—Commerce silt loam, Bruin silt loam, Mhoon silty clay loam and Sharkey clay. In Figure 3, the results of nematode samples collected on a 1-acre grid are overlaid on the elevation map. These graphic depictions indicate that the root-knot nematode infests only a portion of the field. This has allowed the scientists to develop variable rate prescriptions for pesticide treatment, reducing the need for nematicide by 60 percent.
With the help of a grant from the U.S. Environmental Protection Agency, the LSU AgCenter research team will expand its efforts to provide better knowledge of plant parasitic nematode distributions and densities. The team will evaluate several fields with a history of nematodes and develop Veris information, topography data guidance systems and variable rate applications. The objectives of the research include enhanced ability to sample plant parasitic nematodes and creation of GIS/GPS-based strategies that will be user-friendly so producers can more effectively manage plant parasitic nematode infestations. |