Field-Scale Soil Moisture Pattern Mapping using Electromagnetic Induction

11 páginas, 12 figuras, 2 tablas.

Soil apparent electrical conductivity (ECa) responds to time-variable soil properties, such as soil water content (θ), and can therefore be used to characterize the spatial and temporal dynamics of θ at the field scale. When clay content is high and uniform and the θ range small, however, it is not clear whether ECa maps can be used for this purpose. A soil management experiment established in a Vertisol in 1982 was surveyed for ECa on 13 occasions to capture changing soil conditions and to determine the sources of this variability. Less variation with time was found in subsoil than in topsoil ECa patterns, especially within the conventional tillage (CT) plots, in areas with shallow soil, and along the drainage network. Using the 13 ECa relative difference data sets as variables, principal component (PC) analysis showed that the first three PCs explained 90% of their total variance. The time-stable or mean ECa pattern was significantly correlated with PC1 and could also be associated with topography, soil depth, and soil structure but could not be related to a single survey. Topography and soil management could be associated with PC2 and PC3, respectively. Time-stable θ patterns, inferred from 26 surveys, revealed topographical and management characteristics and showed significant relationships (P < 0.001) with ECa–derived patterns like soil porosity and infiltration caused by soil management, topography, and rainfall. Electromagnetic induction sensors were useful for mapping soil spatial variability and changing soil conditions due to management effects and external forcing in uniform clay soils.

This work was funded by INIA and FEDER through Grants RTA2006-00058- CO3-02 and PRE-2005, by the Junta de Andalucía though the Grants AGR-2349 and AGR-4782, and by the Ministry of Science and Innovation and FEDER through Grant AGL2009-12936-C03-03.

Peer reviewed