Soil Salinity Assessment by Electromagnetic Induction of Irrigated Land
1992
Hendrickx, J. M. H. | Baerends, B. | Raza, Z. I. | Sadig, M. | Chaudhry, M Akram
The purpose of this study was to characterize the variability and statistical distribution of electromagnetic induction measurements for salinity assessment on irrigated land. Such information is needed to optimize future sampling schemes. A detailed salinity survey was carried out with an electromagnetic device (Geonics EM38) in a representative experimental area of 37 ha near Faisalabad, Pakistan. The apparent electrical conductivity of the soil was measured at >3400 locations. In addition, a visual agronomic salinity survey was conducted. A linear relation between the standard deviation of the data and their means indicated that the salinity data were log-normally distributed. Therefore, we recommend using log-transformed data for statistical inferences. Geostatistical analysis of the log-transformed data verified that the salinity of a field was principally determined by the irrigation management of the farmer. Significant salinity differences were found between abandoned, fallow, and cropped fields, but not between fields with different crops. We found that the electromagnetic induction meter (EM38) was in good agreement with the visual agronomic survey. The EM38 was superior because it had a better resolution, was more sensitive to salinity changes with depth and spatially, and could be conducted with or without a crop or at any stage of a crop. For random sampling schemes in our experimental area, the budgetary efficiency of the survey improved when entire fields rather than single points were selected for the survey. For salinity sampling with a stratified random sampling scheme, the strata can be based either on land use or on visually observed salinity status.
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