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Geometrical attributes of pore systems in soil have shown fractal scaling. Scaling in natural materials is inherently statistical, i.e., fractal dimensions may change with scale. While fractal dimensions characterizing pore surface roughness, D s , or scaling of pore sizes, D v , have been reported, seldom are both measurements made at more than one scale. We examine a scale effect...
Structural units in freshly tilled soil are mainly fragments derived from tillage. Fractal geometry is potentially useful to model this structure. This research was designed to test the applicability of fractal models for mass- and number-size distributions, and surface roughness of soil fragments produced by tillage; and evaluate relationships among parameters of these fractal models. Fragments were...
Tillage practices and soil texture can influence the dynamics of soil organic matter (SOM) transformations, so that direct indicators of SOM quality are needed to assess its biological, chemical and physical functions. A field study was conducted to investigate the characteristics of diethyl ether (DEE) and chloroform (CHCl 3 ) extractable lipids following a three-year rotation of maize, soybean...
The humic substances (HS) of two Brazilian Oxisols, one under native grassland (NG) and the other submitted to a long-term (19-year) tillage systems experiment including no-tillage (NT), minimal tillage (MT) and an adjacent eucalyptus-planted forest (F), were extracted with sodium pyrophosphate, analysed and fractionated by exclusion chromatography on controlled pore glass (CPG). Chromatographic analysis...
Little is known about the in situ hydrological properties of soils in the semi-arid regions of the world where subsistence agriculture is the common land use. The work reported here concentrates on three major soil types, considered representative of the agriculturally important Zimbabwean fersiallitic group of soils, and describes the water regimes that develop under conventional (flat) and improved...
There is limited information on the application of fractal concepts to Vertisols. The objectives of this study were to: (i) test the applicability of the fractal fragmentation theory to Vertisols and (ii) see whether the parameters of fractal models reflect differences in soil management and with depth. The soil was sampled at 0-10, 10-20, and 20-40 cm depths in early May 1998, 15 days after the rice...
Despite that dissolved organic matter (DOM) and water-extractable organic matter (WEOM) represent only a small part of soil organic matter, they appear to be involved in many soil processes. This review intends to compile the current information on the influence of land use and management practices on soil DOM and WEOM, and to identify the gaps in our knowledge that sometimes preclude from drawing...
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...
The index of soil physical quality, S, which was introduced in Part I is applied to problems of agricultural soil mechanics, especially soil tillage and hard-setting. S is equal to the slope of the water retention curve at its inflection point. The retention curve must be plotted as the logarithm (to base e) of the water potential against the gravimetric water content (kg kg -1 ). The...
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”),...
The content and fractional composition of humus in soil exposed to conventional, shallow and minimum tillage for 40 years was investigated on Cambisols. Humus status depended on tillage methods and depth. In cultivated soil, conventional annual tillage can be replaced by shallow or minimum tillage, since this significantly increased soil humus content in the 0–10 and 10–20 cm soil layers. In both...
Rainfed permanent crops such as almonds, olives and vines cover important areas in the drier parts of the Mediterranean. The acreage of almonds has expanded rapidly into marginal soils of the hillslopes of southeast Spain. This expansion starting in the 1970s was reinforced by the subsidies under the EU Common Agricultural Policy since the late 1980s. Trees are widely spaced and the soil in between...
Soil aggregation plays a crucial role in soil physicochemical and biological processes, thus influencing soil nutrient retention. It is possible to improve soil aggregation by choosing appropriate agricultural practices. The objective of this study was to evaluate the effects of tillage, crops and fertilizer sources on size distribution of water-stable aggregates (WSA) and nutrient concentrations...
Soil surface roughness is known to influence water infiltration, runoff and erosion. Soil surface roughness changes with management and weather and its mathematical description still remains an important issue. The main objective of this study was to investigate the effect of tillage on the two fractal indices, fractal dimension, D, and crossover length, l, currently used in characterizing soil surface...
The effect of management systems and crop rotation on soil phosphorus (P) fractions and selected soil properties were studied from 2002 to 2005 on an experiment established in 2001 in a volcanic derived Ultisol from southern Chile. Two tillage systems, no tillage (NT) and conventional tillage (CT), and two crop rotations, oat–wheat and white lupine–wheat were evaluated in order to determine the effects...
The objective of this study was to explore if more crop-specific plant growth modules can improve simulations of crop yields, and N in tile flow under different management practices compared with a generic plant growth module. We calibrated and evaluated the Root Zone Water Quality Model (RZWQM) with the Decision Support for Agrotechnology Transfer (DSSAT v3.5) plant growth modules (RZWQM–DSSAT) for...
Agricultural system models are tools to represent and understand major processes and their interactions in agricultural systems. We used the Root Zone Water Quality Model (RZWQM) with 26 years of data from a study near Nashua, IA to evaluate year to year crop yield, water, and N balances. The model was calibrated using data from one 0.4 ha plot and evaluated by comparing simulated values with data...
An extensive soil condition assessment should include some appropriate tools to measure crop management influence on the soil condition. Univariate (partial regressions) and multivariate (canonical correspondence analysis, partial canonical analysis of correspondence and the method of variation partitioning) were used to determine the independent and joint effects of crop management and the spatial...
Alarming erosion rates have been reported in olive groves on sloping and mountainous land with some regional averages supposedly as high as 40–100 ton ha −1 yr −1 . These figures are based on empirical models that apply a simple multiplication of adverse environmental factors such as steep slopes, erodible soils and low vegetation cover. We present experimental data from rainfall simulations,...
The objective of this study was to examine the interactive effects of tillage and land forms (erodibility) on the redistribution of C, N and P within an agricultural landscape. Soils were sampled from an undulating maize field in central Belgium. Half of the field was under conventional tillage (CT), while the rest was under minimum tillage (MT) management. Based on slope and curvature characteristics,...
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