Concurrent temporal stability of the apparent electrical conductivity and soil water content

Authors: PEDRERA-PARRILLA, AURA - IFAPA CENTRO ALAMEDA DEL OBISPO; Pachepsky, Yakov; TAGUAS, ENCARNACION - UNIVERSIDAD DE CORDOBA; MARTOS-ROSILLO, SERGIO - IFAPA CENTRO ALAMEDA DEL OBISPO; GIRALDES, JUAN - UNIVERSIDAD DE CORDOBA; VANDERLINDEN, KARL - IFAPA CENTRO ALAMEDA DEL OBISPO

Submitted to: Journal of Hydrology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/28/2016
Publication Date: N/A
Citation: N/A

Interpretive Summary: Overland pollutant transport and crop yields are strongly affected by soil water content. It is beneficial to find locations in the fields where soil water content is persistently higher and persistently lower than the average. Finding such locations via intensive water measurement is prohibitively time- and labor-consuming and, in most cases, impractical on farms. Soil electrical conductivity reflects soil water content; intensive sampling using soil electric conductivity has recently become feasible. Our objective was to test the hypothesis that the areas of persistently higher and persistently lower electrical conductivity are consistent with areas of persistently higher and lower soil water contents. We tested this hypothesis on sandy soils in an orchard, and found that indeed the areas ranked as having high, medium and low electrical conductivity substantially overlapped with the similarly ranked areas of soil water content. Results of this work can be useful to farmers and consultants in that they show the opportunity to establish zones with distinctly different soil water contents based on soil electrical conductivity surveys.

Technical Abstract: Knowledge of spatio-temporal soil water content (SWC) variability within agricultural fields is useful to improve crop management. Spatial patterns of soil water contents can be characterized using the temporal stability analysis, however high density sampling is required. Soil apparent electrical conductivity (ECa) measurements with high spatial density have been widely used to infer the spatial variability of soil water content. The objective of this work is to test the hypothesis that ECa temporal stability can be demonstrated and the relationships between temporal stability patterns of water contents and ECa can be established. The experimental catchment, “La Manga”, is located in SW Spain and covers 6.7 ha of rainfed olive orchard. ECa field-wide surveys and gravimetric soil water sampling were performed on six and eighteen dates, respectively. Temporal stability was evaluated for both soil variables. ECa spatial patterns were used to identify three zones with ECa values of similar magnitude, substantially lower or substantially greater than the spatial mean. The same was done for SWC. The locations with SWS close to average were found mostly in the zone with ECa close to average. The relationships between the spatial mean SWC and the corresponding location values were approximated with linear, exponential and power law regressions for each sampling location, and the Akaike Information Criteria was used to define the best fit among them. The non-linearity precluded using some locations as the representative ones. Overall, temporal stability analysis of ECa can help to find the representative for SWCs in the field.