Papers by Gonzalo Martinez
Soil water content (SWC) is a key variable for numerous physical, chemical and biological process... more Soil water content (SWC) is a key variable for numerous physical, chemical and biological processes that take place at or near the soil surface. Understanding the spatial and temporal variability of SWC at the field scale is of prime importance for implementing efficient measurement strategies in applications. An experimental field in SW Spain, where conventional (CT) and no-till (NT) management on a heavy clay soil are being compared since 1983, was sampled for gravimetric SWC on 38 occasions during 2008 and 2009. Topsoil clay content across the six plots is on average 55%, with a standard deviation of 2.7%. The soil profile was sampled at 54 locations, evenly distributed over the three CT and NT plots, at depths of 0-10, 25-35, and 55-65 cm. In addition, at 18 of the 54 points PVC access tubes were installed and SWC was measured on 64 occasions during the same period, using a Diviner 2000 capacitance probe (Sentek Sensor Technologies, Stepney, Australia). Measurements were made wi...
Soil water content (θ) is one of the most important drivers for many biogeochemichal fluxes at di... more Soil water content (θ) is one of the most important drivers for many biogeochemichal fluxes at different temporal and spatial scales. Hydrogeophysical non-invasive sensors that measure the soil apparent electrical conductivity (ECa) have been widely used to infer spatial and temporal patterns of θ. Empirical, time and location-dependent, regressions are usual to relate ECa and θ. These relations typically are weak in soils with high content of clay. The objective of this work has been to demonstrate an opportunity to improve the θ estimation in a clayey soil for any given time using spatially collocated time-lapse ECa surveys. The experiment was carried out at a field site with two different types of soil management. Total of 17 gravimetric soil water content sampling campaigns of the top 0.35 m and 13 topsoil ECa surveys have been performed. The studied periods were from January 2008 to May 2009 for θ and from March 2006 to February 2009 for ECa. Three of soil water content and ECa...
Journal of Hydrology, 2013
Occurrence of temporal stability of soil water content has been observed for a range of soil and ... more Occurrence of temporal stability of soil water content has been observed for a range of soil and landscape conditions and is generally explained as a consequence of local and non-local controls. However, the underlying factors for this phenomenon are not completely understood and have not been quantified. This work attempts to elucidate and quantify the effects of several local controls, such as soil hydraulic properties and root water uptake, through water flow simulations. One-dimensional water flow was simulated with the HYDRUS code for bare and grassed sandy loam, loam and clay soils at different levels of variability in the saturated hydraulic conductivity K sat . Soil water content at 0.05 and 0.60 m and the average water content of the top 1 m were analyzed. Temporal stability was characterized by calculating the mean relative differences of soil water content in 100 soil columns used for each combination of soil and season. Using log-normal distributions of K sat resulted in mean relative differences distributions that were commonly observed in experimental studies of soil water content variability. Linear relationships were observed between scaling factor of ln K sat and spread of the mean relative differences distributions. For the same scaling factor and soil texture, simulated shapes of the mean relative differences distributions depended on the duration of the simulation period and the season. Variation in mean relative differences was higher in coarser textures than in finer ones and more variability was seen in the topsoil than in the subsoil. Root water uptake decreased the mean relative differences variability in the root zone and increased variability below it. This work presents a preliminary research to promote the use of water flow simulations under site-specific conditions to better understand the temporal stability of soil water contents. The estimation of the spatial variability of K sat from soil water content monitoring presents an interesting avenue for further research.
Knowledge on the spatial soil moisture pattern can improve the characterisation of the hydrologic... more Knowledge on the spatial soil moisture pattern can improve the characterisation of the hydrological response of either field-plots or small watersheds. Near-surface geophysical methods, such as electromagnetic induction (EMI), provide a means to map such patterns using non-invasive and non-destructive measurements of the soil apparent electrical conductivity (EC a . In this study EC a was measured using an EMI sensor and used to characterize spatially the hydrologic response of a cropped field to an intense shower.
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Papers by Gonzalo Martinez