ISHS Acta Horticulturae 278: Symposium on Scheduling of Irrigation for Vegetable Crops under Field Condition
STUDY OF THE SPATIAL VARIABILITY OF SOIL-WATER CHARACTERISTICS |
| Authors: | A. Castrignanò, G. Lopez |
| Abstract:
In order to study spatially variable soil-water characteristics, 45 disturbed cores were taken to a depth of 40 cm. The area test was located at the experimental farm of the Experimental Agronomic Institute, near Foggia (Southern Italy) on a bare silty-clay soil (Vertisol, Typic Chromoxerert). The measurements of soil-water content O and matric potential h, made in laboratory, were fitted to the five parameter van Genuchten model, for each site as well as for all data; then the probability density distributions of each parameter were studied. In order to reduce the scatter of data points around the mean soil-water characteristic curve, observations have been scaled by using the concept of similar media, introduced by Miller and Miller (1956). The scale factors of this analysis were derived from an empirical method called "functional normalization", based on least square regression analysis. We chose a simplified expression of the van Genuchten model to describe the analytical relationship between matric potential and saturation degree. This method allowed all relationships relative to each site to coalesce into a single reference curve that describes the data set as a whole. By the normalization procedure we determined one scale factor for each site relating the data measured at each location to the reference curve. Also, the frequency distribution of scale factors was determined and was found normal. | |
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