With an objective to link the hydraulic properties of soil with the soil structural properties, air permeability and 5% arrival time of a conservative tracer was measured for large undisturbed soil columns from the same agricultural field. The same soil columns were scanned with a medical scanner from which macropores present in each of the soil column could be reconstructed and quantified after processing of the images. From the images, the total macro-porosity in a soil column and macro-porosity of the restricting layer (limiting quarter) for each sample were quantified and correlated with air permeability and 5% arrival time. Even in the same field high variability in air permeability, ranging from 4.66 to 78.10 µm2, and 5% arrival time of tracer (0.07 to 2.36 h) were observed between the samples. Both air permeability and 5% arrival time of tracer were strongly correlated with macro-porosity (R2 = 0.80 for air permeability: R2= 0.61 for 5% arrival time) and macro-porosity of the restricting layer (R2=0.83 for air permeability: R2= 0.71 for 5% arrival time) over air-filled porosity and all the correlations were positive. The high positive correlation these air and water transport functions with macro-porosity stressed the importance of continuity and tortuosity of pores in air, water and solute flow and transport through the soils. Negative correlations of air permeability, 5% arrival time of tracer and macro-porosity were obtained with bulk density whereas with other soil physical properties such as clay, sand and organic matter content they were only weakly correlated. From the study it was found that quantification of pore characteristics is important in understanding the flow and transport behavior of soils but proper quantification of the much easily measurable macro-porosity is more important.
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ASA, CSSA and SSSA International Annual Meetings, 2012