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For the uplifted coral atolls of the Loyalty Islands (New Caledonia), the prime source of potable water is the freshwater lenses that underlie the islands. The recent adoption of more-intensive agricultural practices, particularly the use of nitrogeneous fertilizers, may, however, represent a threat for these fragile Pacific ecosystems. To assess the risk posed by nitrate leaching, experiments have...
The capacity of soils to supply water to growing plants was expressed in a static and dynamic manner by calculating 'available water' (AW) and the 'soil moisture supply capacity' (MSC), respectively. Four methods of increasing complexity were compared for the AW and two for the MSC, using measured moisture retention and hydraulic conductivity curves and data derived from class- and continuous pedotransferfunctions...
Soil deformation and unsaturated transient water flow in swelling soil on a laboratory scale is predicted using a one-dimensional numerical model. The model is based on a soil water flow equation and extended to soil deformation using Lagrangian description (LD). The specific features of the model are inclusion of an overburden component in the total potential of the flow equation, introduction of...
Interest in site-specific agronomic management in intensively cropped regions necessitates characterization of subsurface water movement for efficient water management (irrigation timing) and control of off-site agrichemical movement. Soils formed in fluvial sediments in portions of the Upper Coastal Plain of Georgia (USA) are extensively used for peanut, cotton, and corn production. Certain proximate...
A formal analysis was carried out to evaluate the efficiency of the different methods in predicting water retention and hydraulic conductivity. Efficiency can be defined in terms of effort, cost or value of information. The analysis identified the contribution of individual sources of measurement errors to the overall uncertainty. The value of information summarises the quality of the prediction,...
The aim of this investigation was to check the capability of the Mualem/van Genuchten model to predict unsaturated soil hydraulic conductivity values from water retention data in the absence of spatial variability and effects of macropores. Furthermore, different techniques of parameter estimation were tested.Soil cores of 250 cm 3 were filled with a repacked silty loam soil. After measuring...
The stress-strain processes in structured unsaturated arable and forest soils depend very much on the internal soil strength and on the existing hydraulic and mechanical boundary conditions. These variables affect soil deformation by compaction and shearing to a great extent. As soon as the internal soil strength, defined as the precompression stress value, is exceeded by external forces, an intense...
Conversion of cropland to perennial grasses will, over time, produce changes in soil hydraulic properties. The objective of this study was to characterize and compare hydraulic properties of fine-textured soils on adjacent native grassland, recently tilled cropland, and reestablished grassland in the Conservation Reserve Program (CRP) at three locations in the Southern Great Plains. A tension infiltrometer...
Evaporation is a major component of the water loss from the soil whose structure is modified by traffic and tillage. This study was undertaken to analyse, in field conditions, the effect of tillage and traffic on soil structure and evaporation, and to determine the role of the change in hydraulic properties on soil drying using water transfer model. Three structures of the ploughed layer were formed...
Water sometimes infiltrates into a sandy soil along preferential flow paths called fingers, rather than homogeneously. In order to understand the physical fundamentals of fingering flow, we carried out two-dimensional infiltration tests under continuous rainfall. Each finger was composed of two moisture structure zones, a finger core and a finger-swelling zone surrounding the finger core. Each finger...
The accurate determination of the wetting soil hydraulic properties for a wide range of water contents is essential for studying and predicting infiltration processes. We present a laboratory infiltration method for determining hydraulic conductivity function, K(θ), in the low-to-medium water content range. An initially air-dry soil core is subjected to infiltration from the bottom where the pressure...
Ferralsols under native vegetation have a weak to moderate macrostructure and a well-developed microstructure corresponding to subrounded microaggregates that are usually 80 to 300 μm in size. The aim of this study was to analyze how the hydraulic properties of a clay Ferralsol were affected by a change of structure when the native vegetation is cleared for pasture. We studied the macrostructure in...
The index of soil physical quality, S, which was proposed in Part I and which was applied to the problems of tillage in Part II is applied in Part III to the unsaturated hydraulic conductivity of soil. S is equal to the slope of the soil water retention curve at its inflection point. This curve must be plotted as the logarithm (to base e) of the water potential against the gravimetric water content...
Little is known about the sustainability of irrigated oasis agriculture in northern Oman. The objective of this study therefore was to examine which factors allowed agricultural productivity to be apparently maintained during the two millenia of a mountain oasis' existence. Soil moisture and physico-chemical properties were measured in a typical flood-irrigated field sown to alfalfa (Medicago sativa...
The soil formation process ripening can be used as a bioremediation technique for dredged sediments that are polluted with organic chemicals. Currently, data are lacking that quantify the effects of physical ripening on parameters that affect aerobic bioremediation. We quantified the effects of physical ripening on shrinkage, swelling, moisture retention, hydraulic conductivity, and oxygen diffusion...
A 13-year long-term experiment on the Loess Plateau of China was used to evaluate the effect of two different fertilizer regimes on the soil's physical/hydraulic properties. The fertilizer regimes included (i) control without any fertilizer (C), (ii) applications of chemical fertilizer (NPK), and (iii) applications of chemical fertilizer plus dairy manure (MNPK). Undisturbed soil cores were collected...
Use of treated wastewater (TWW) for irrigation of semiarid and arid soils may lead to degradation of soil hydraulic properties, the magnitude of which may depend on the type of the irrigation system. Most studies evaluated the impact of irrigation with TWW on soil hydraulic conductivity (HC) using repacked samples, which do not necessarily represent soil field conditions. Our objectives were to (i)...
Direct determination of soil hydraulic properties is often costly and laborious hence the use of indirect methods such as pedotransfer functions (PTFs). Despite progress made in PTF development in general, little evaluation of PTFs has been done for the sandy soils of Niger. We tested the ability of three PTFs, (Campbell, van Genuchten, and Vauclin) to determine soil water retention and unsaturated...
Re-packed soil columns of the Crediton series were sown with white clover or perennial ryegrass, with nitrate managed according to organic and conventional farming regimes respectively. Visual observations revealed a rapid enhancement in soil structure beneath white clover compared to ryegrass and unplanted soil. Enhanced structural differentiation beneath white clover was supported by greater permeability...
The Priorat region, a traditional area for wine production in the Mediterranean mountain environment of NE Spain, has been undergoing drastic changes since the 1990s, with the conversion of abandoned and natural vegetation areas into new terraced vineyard plantations. In most cases, these land cover changes involve land terracing, with risers more than 2 m high and benches with the soil surface structure...
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