Spatial variability of four selected properties in a one-hectare field from Central Jordan Valley [geostatistical analyses; probability plot for lognormal value and semivariogram construction; GEO-EAS program]
1992
Abu-Sharar, T.M. | Saffarini, G. (Jordan Univ., Amman (Jordan))
A squared 1 ha field from Deir-Alla in the Central Jordan Valley was chosen to study the spatial variability of four soil properties: electrical conductivity of the paste extract (EC), sand content, NH4, OAC-extractable K, and NaHCO3 extractable P. The diagonals of the field were employed as transects (NW-SE and NE-SW) to collect soil samples on 4m intervals. Such a sampling scheme allowed data analysis using both conventional statistics and geostatistics. By dividing the field into 18 squared subplots of common center (diagonal intersection) and increasing area, the ratio of each area to the number of soil samples contained in that area (AR) and the coefficient of variation (CV%) for the given property pertaining to the respective area were calculated. The CV% decreased with increasing AR to a threshold value beyond which the CV% either remained relatively constant (EC and sand content) or increased. The CV% of the NAHCO3-extractable P increased to a relatively high and stable level beyond the AR threshold value of 40m2/sample. Semivariograms were constructed for each transect and for entire field using the GEO-EAS program. Results showed that all the parameters were anisotropic in nature. All semivariograms representing the entire field were fit to the linear model with the greatest and smallest dependance of on "h" being for NAHCO3 extractable P and sand content, respectively.
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