Biological Systems Engineering



Mohamed F. Dahab

Date of this Version



Goderya, F. S., Dahab, M. F., Woldt, W. E., Bogardi, I., "Spatial Patterns of Field Measured Residual Soil Nitrate," Geostatistics for Environmental and Geotechnical Applications, ASTM STP 1283, R. Mohan Srivastava, Shahrokh Rouhani, Marc V. Cromer, A. Ivan Johnson, Alexander J. Desbarats, Eds., American Society for Testing and Materials, 1996.


Copyright 1996 by ASTM International. Used by permission.


The purpose of this study was to assess the spatial variability of residual soil nitrate, measured in three contiguous 16 ha fields. Available data for residual soil nitrate were examined using conventional statistics. Data tended to be skewed with the mean greater than the median. Geostatistical methods were used to characterize and model the spatial structure. Three dimensional spatial variability was examined using two semivariograms: horizontal-spatial and vertical. Two dimensional horizontal-spatial semivariograms were also computed for each 0.3m (1ft) layer. Semivariogram analysis showed that there were similarities in the patterns of spatial variability for all fields. The results suggest that the spatial patterns in residual soil nitrate may be correlated with irrigation practices. Furthermore, a trend was found to be present along the vertical direction, which may be related to the time of sampling.