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Abstract: The management of irrigated agricultural fields requires reliable information about soil hydraulic properties and their spatio-temporal variability. The spatial variability of saturated hydraulic conductivity, K s and the alpha-parameter α vG-2007 of the van Genuchten equation was reviewed on an agricultural loamy soil after a 17-year period of repeated conventional agricultural practices for tillage and planting. The Beerkan infiltration method and its algorithm BEST were used to characterize the soil through the van Genuchten and Brooks and Corey equations. Forty field measurements were made at each node of a 6m×7.5m grid. The soil hydraulic properties and their spatial structure were compared to those recorded in 1990 on the same field soil, through the exponential form of the soil hydraulic conductivity given by the Gardner equation, using the Guelph Pressure Infiltrometer technique. No significant differences in the results obtained in 1990 and 2007 were observed for either particle-size distribution or dry bulk density. The mean value of α vG-2007 was found to be identical to that of α G-1990, while that of K s-2007 was significantly smaller than that of K s-1990. In contrast to the Gardner equation, the van Genuchten/Brooks and Corey expression was found to be more representative of a well-graded particle-size distribution of a loamy soil. The geostatistical analysis showed the two parameters, K s and αvG-2007, were autocorrelated up to about 30 and 21m, respectively, as well as spatially positively correlated within a range of 30m. Despite the difference in the mean values of K s between the two studies, the spatial structures were similar to those found in the 1990 experiment except for the covariance sign. The similarity in autocorrelation ranges indicate that the spatial analysis of soil hydraulic properties is independent of the infiltration methods (i.e., measurement of an infiltration flux) used in the two studies, while the difference in the covariance sign may be linked to the use of two different techniques of soil hydraulic parameterization. The covariance values found in the 2007 campaign indicates a positive relationship between the two parameters, K s and α vG-2007. The spatial correlations of soil hydraulic parameters appear to be temporally stabilized, at least within the agro-pedo-climatic context of the study. This may be attributed to the soil textural properties which remain constant in time and to the structural properties which are constantly renewed by the cyclic agricultural practices. However, further experiments are needed to strengthen this result. [Copyright &y& Elsevier]

Abstract: About 2000 active faults are known to exist within the land area of Japan. Most of these active faults have deformed the topographic surfaces which were formed in the late Quaternary, including fluvial terraces; and the formative ages of these terraces are estimated mainly by tephrochronology. Fluvial terraces in the eastern Hokuriku region, comprising the Toyama, Tonami, and Kanazawa Plains, northern central Japan, are widely distributed and have been deformed by reverse active faults. The formative age of terraces in this area has not been reported, as volcanic ash deposits are rarely visible within terrace deposits and the overlying loamy soil, and outcrops of fluvial terraces are quite scarce in this area. In the present study, we carried out a drilling survey on these terraces to obtain samples of the overlying loamy soil and upper part of terrace deposits. From these samples, we extracted some well-known widespread volcanic ash, from which we were able to estimate the approximate age of the terraces and the vertical slip rate of the active faults. Late Quaternary fluvial terraces in eastern Hokuriku are divided into 12 levels: Terraces 1 to 12 in descending order. Widespread tephras such as the Kikai-Tozurahara Tephra (K-Tz: 95 ka) are contained in the lowest part of the loamy soil in Terrace 4 and the Daisen-Kurayoshi Pumice (DKP: 55 ka) is present in the lowest part of the loamy soil in Terrace 6. From the ages and the vertical displacements of the fluvial terraces, the late Quaternary average vertical slip rates of active faults in eastern Hokuriku are estimated to be 0.2–0.9 mm/year (Uozu fault), 0.1–0.4 mm/year (Kurehayama fault), 0.1–0.3 mm/year (Takashozu fault), 0.1–0.4 mm/year (Hohrinji fault), and 0.5–0.8 mm/year (Morimoto-Togashi fault). We also estimated the recurrence interval of earthquakes related to active faults from displacement per event and ages of terraces and no significant difference in vertical displacement per single earthquake for different active faults, and recurrence intervals tend to be inversely proportional to vertical displacement rates. This study demonstrates that a combination of drilling of loamy soil and precise cryptotephra analysis of fluvial terraces can be used to estimate the formative age of the terraces and the average slip rate of active faults in areas where volcanic ash deposits are rare. [Copyright &y& Elsevier]

Abstract: Hydraulic conductivity is an important parameter of water and solute transport in soils. Hydraulic conductivity is known to be highly variable in space, but its dependence on soil horizonation has seldom been explored. We measured the near-saturated hydraulic conductivity of three soils located in the Centre of France, a Néoluvisol, a Calcisol, and a Calcosol (according to the “Référentiel Pédologique”), using tension disc infiltrometry. The Reynolds and Elrick''s multipotential technique has been applied to the steady state infiltration kinetics measured at potentials −1.5, −0.6, −0.3, −0.1 and −0.05 kPa to derive the hydraulic conductivity values. Each horizon of the three soil profiles has been characterised at least once at three locations 50-cm apart from each other on a flat surface prepared within the same access pit. Some horizons have been characterised on a second occasion in other access pits opened at nearly 10 m from the previous ones. On average, hydraulic conductivity values increased from 1.3×10−7 m/s at −1.5 kPa to 2.5×10−6 m/s at −0.3 kPa. Saturated hydraulic conductivity varied between 3.6×10−6 m/s for the ploughed layer of the Calcosol and 4.9×10−3 m/s for the Calcosol substrate (C horizon). The various horizons of the Néoluvisol had hydraulic conductivity values which were not significantly different from each other, except the ploughed layer which had lower hydraulic conductivity values than the underlying horizons. The tilled layers of the Calcisol and the Calcosol also had lower hydraulic conductivity values than their respective underlying cambic horizons. Further, the hydraulic conductivity of the tilled layer of the Calcosol was lower than that of the tilled layers of the Calcisol and the Néoluvisol. This difference was attributed to the effect of different tillage systems, the Calcosol being superficially tilled while the Calcisol and Néoluvisol were ploughed each year. The structural S cambic horizons of the Calcisol and Calcosol had similar hydraulic conductivities but lower than their respective substrate (limestone). [Copyright &y& Elsevier]