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Title: Delineation of Management Zones for Site Specific Management of Parasitic Nematodes Using Geostatistical Analysis of Measured Field Characteristics

Author
item ORTIZ, B - UNIVERSITY OF GEORGIA
item Sullivan, Dana
item PERRY, C - GA
item VELLIDIS, G - UNIVERSITY OF GEORGIA

Submitted to: European Conference on Precision Agriculture Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 3/12/2007
Publication Date: 6/3/2007
Citation: Ortiz, B.V., Sullivan, D.G., Perry, C., Vellidis, G. 2007. Delineation of Management Zones for Site Specific Management of Parasitic Nematodes Using Geostatistical Analysis of Measured Field Characteristics. 6th European Conference on Precision Agriculture Proceedings.

Interpretive Summary: Delineation of management zones for site specific management of cotton-parasitic nematodes requires the study of their spatial and temporal variability. The study involved the analysis of the spatial variability of the southern root knot nematode (Melodogyne incognita) and its spatial correlation with soil texture, soil electrical conductivity, elevation, slope, and spectral reflectance in 10 cotton fields in Georgia, USA in 2005 and 2006. Continuous data sets were developed for soil electrical conductivity, elevation, and slope. Spectral reflectance was obtained 4 times during the growing season from a 4-band multispectral camera mounted on an aircraft platform and used to develop several indices including the normalized difference vegetation index (NDVI). A systematic sampling design with square grids of 0.20 ha in size was used to sample nematodes prior to, during, and after the growing season. The 2005 results indicate that NDVI and elevation showed significant advantages in reducing the root knot nematode within-zone variability and could be used to create management zones for site-specific application of nematicides. The 2006 season is still in progress but results will be available for inclusion in the conference proceeding.

Technical Abstract: Delineation of management zones for site specific management of cotton-parasitic nematodes requires the study of their spatial and temporal variability. If the nematodes follow a spatial structure and this structure is correlated with the spatial variability of specific biotic or abiotic conditions present in the field, those conditions can be used as surrogate data to identify areas at risk of cotton yield reduction due to nematode damage. The study involved the analysis of the spatial variability of the southern root knot nematode (Melodogyn incognita) and its spatial correlation with soil texture, soil electrical conductivity, elevation, slope, and spectral reflectance in 10 cotton fields in Georgia, USA in 2005 and 2006. Continuous data sets were developed for soil electrical conductivity, elevation, and slope. Spectral reflectance was obtained 4 times during the growing season from a 4-band multispectral camera mounted on an aircraft platform and used to develop several indices inducing the normalized difference vegetation index (NDVI). A systematic sampling design with square grids of 0.20 ha in size was used to sample nematodes prior to, during, and after the growing season. Because it is known that nematodes are prone on sandy areas, soil cores of 1-m long for soil texture assessment were also collected. The soil cores were taken based on a proportional stratified random sampling design where the strata were zones delineated based on soil electrical conductivity data. Geostatistical analyses to study the spatial variability of the variables under analysis involved the calculation of semivariograms, identification of the degree of spatial structure, kriging interpolations, and cross correlograms for each variable under study. Areas having a high probability of nematode populations above threshold values were identified through analyses of Indicator and Disjunctive kriging of the variables strongly related with the nematodes’ spatial variability. The 2005 results indicate that NDVI and elevation showed significant advantages in reducing the root knot nematode within-zone variability and could be used to create management zones for site-specific application of nematicides. The 2006 season is still in progress but results will be available for inclusion in the conference proceeding. In this paper we will present the results of the two year study and make recommendations on the most efficient approach for creating management zones for site-specific control of root knot nematode in cotton.