SW—Soil and Water: Soil Macroporosity Distribution and Trends in a No-till Plot using a Volume Computer Tomography Scanner

Abstract Soil macroporosity (voids with a diameter of 0·54 mm or more) was estimated in undisturbed soil columns obtained from eight 1 m by 1 m plots of a no-till field using image analysis, the soil samples having been scanned with a laboratory volume computer tomography (CT) scanner. Estimates of soil macroporosities in the A horizon, the B horizon and the entire field were found to be log-normally distributed. For the entire depth under consideration (0–400 mm), and the A horizon (0–200 mm), there was a significant decreasing trend in the soil macroporosity with depth. In the B horizon, the soil macroporosity showed neither a decreasing or increasing trend with depth. Using the Kolmogorov–Smirnov two-sample test, it was observed that both the physical and mechanical processes creating the soil macropores in the A and B horizons were completely different or if they were the same then the extent of the physical and mechanical processes involved in soil macropore formation were completely different e.g. the number of earthworms present in each horizon based on the availability of residue which acts as food and the number and type of plants roots available at each horizon.

[1]  Janice L. Stolzy,et al.  Effects of spatial variability of soil hydraulic properties in water budget modeling , 1977 .

[2]  Tammo S. Steenhuis,et al.  Preferential movement of pesticides and tracers in agricultural soils , 1990 .

[3]  L. Barker,et al.  Spatial Variability in Alluvium Properties at a Low-Level Nuclear Waste Site , 1994 .

[4]  Aaron Fenster,et al.  Quantification of soil macroporosity and its relationship with soil properties , 1999 .

[5]  A. Wild,et al.  USE OF FLUORESCENT DYES TO MARK THE PATHWAYS OF SOLUTE MOVEMENT THROUGH SOILS UNDER LEACHING CONDITIONS: 2. FIELD EXPERIMENTS , 1979 .

[6]  A Fenster,et al.  A high-resolution XRII-based quantitative volume CT scanner. , 1993, Medical physics.

[7]  G. W. Thomas,et al.  Chloride and Tritiated Water Flow in Disturbed and Undisturbed Soil Cores1 , 1974 .

[8]  P. Bullock,et al.  Rothamsted studies of soil structure II. Measurement and characterisation of macroporosity by image analysis and comparison with data from water retention measurements , 1979 .

[9]  T. J. Gish,et al.  PREFERENTIAL MOVEMENT OF ATRAZINE AND CYANAZINE UNDER FIELD CONDITIONS , 1991 .

[10]  R. E. Phillips,et al.  Spatial Distribution of Water and Chloride Macropore Flow in a Well-Structured Soil , 1994 .

[11]  John L. Nieber,et al.  Characterizing Macropores in Soil by Computed Tomography , 1989 .

[12]  J. W. Biggar,et al.  Miscible Displacement: II. Behavior of Tracers1 , 1962 .

[13]  Richard W. Healy,et al.  Variability of an unsaturated sand unit underlying a radioactive- waste trench , 1991 .

[14]  W. Ehlers,et al.  OBSERVATIONS ON EARTHWORM CHANNELS AND INFILTRATION ON TILLED AND UNTILLED LOESS SOIL , 1975 .

[15]  R. Protz,et al.  Comparison of morphology and porosity of a soil under conventional and zero tillage , 1987 .

[16]  L. D. Norton,et al.  Characterizing macropores that affect infiltration into nontilled soil , 1988 .

[17]  Joseph B. Murphey,et al.  FIBERGLASS ENCASEMENT OF LARGE, UNDISTURBED, WEAKLY COHESIVE SOIL SAMPLES , 1981 .

[18]  C. Axness,et al.  Three‐dimensional stochastic analysis of macrodispersion in aquifers , 1983 .

[19]  M. Sharma,et al.  Spatial variability of infiltration in a watershed , 1980 .

[20]  D. R. Nielsen,et al.  Spatial variability of field-measured soil-water properties , 1973 .

[21]  R. J. Luxmoore,et al.  Estimating Macroporosity in a Forest Watershed by use of a Tension Infiltrometer1 , 1986 .

[22]  Masoud Ghodrati,et al.  Preferential transport of nitrate through soil columns containing root channels , 1994 .

[23]  A. W. Warrick,et al.  13 – Spatial Variability of Soil Physical Properties in the Field , 1980 .