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Evaluation of sampling and interpolation methods used for weed mapping

Summary
Weed mapping was carried out on 3 fields in central Bohemia in order to characterize the spatial structure and temporal stability of weed populations over six years (1999-2004). A rectangular grid 40 x 40 m or 20 x 40 m respectively was established applying GPS (Global Positioning System) along the wheel tracks on trial fields. The number of plants for each species and the total weed coverage has been recorded at the grid points. The resulting weed map is strongly affected by the sampling intensity and by the interpolation method used. This paper evaluates the quality of weed maps created using different sampling grids and sample sizes and compares recently used interpolation methods (Ordinary Point Kriging and Inverse Distance Weighting (IDW)). Sample size was found to be critical, particularly for weed species having low economic thresholds such as Galium aparine L. Kriging produced smoothed maps, when a spherical variogram model was used, IDW resulted in artificial contours with spots around the grid points if the setting of Power = 2 were used.

german version

Keywords/Stichworte:Weed mapping; spatial variability; interpolation; Kriging

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Autor:P. HAMOUZ, K. NOVÁKOVÁ, J. SOUKUP, L. TYŠER, Czech University of Agriculture, dpt. of General Plant Production, Kamycka 957, 165 21, Prague 6, Czech Republic, e-mail: hamouzp@af.czu.cz, novakovak@af.czu.cz, soukup@af.czu.cz, tyser@af.czu.cz

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