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Title: SPATIAL ANALYSIS OF THE SATURATED HYDRAULIC CONDUCTIVITY OF A SOIL WITH MACROPORES

Author
item MALLANTS, D. - KATHOLIEKE UNIV LEUVEN
item MOHANTY, B. - U.C. RIVERSIDE
item VERVOORT, A. - KATHOLIEKE UNIV LEUVEN
item FEYEN, J. - KATHOLIEKE UNIV LEUVEN

Submitted to: Soil Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/12/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Different pore groups including macropores, mesopores, and micropores in soil conduct water under saturated condition. The saturated hydraulic conductivity is by far the most important soil hydraulic parameter for it determines the rate of water and solute transmission through the complex network of soil pores. Research indicated its determination is somewhat dependant on sampling volume containing different numbers and sizes of pores. We studied the spatial variability of saturated hydraulic conductivity measured at different spatial locations in a sandy loam soil using three different column sizes (diameter and length). Mean and variance of saturated hydraulic conductivity decreased and spatial structure improved with increasing column sizes. In addition percentage of macropore cross-sectional area decreased with soil depth and found to have moderate spatial variability. Spatial structure of depth-averaged macropore area was found to be correlated with that of saturated hydraulic conductivity indicating morphological parameters offer potentials to better predict hydraulic parameters for soil and water management.

Technical Abstract: We evaluated the spatial variability of laboratory saturated hydraulic conductivity (Ks) measurements in a sandy loam soil using three different column sizes: (i) sixty 5.1-cm long and 5-cm diameter cores (type-I), (ii) thirty 20-cm long and 20-cm diameter columns (type-II), and (iii) thirty 100-cm long and 30-cm diameter columns (type-III). Estimates of macroporosity at three depths (2.5, 12.5, and 16.5 cm) for twenty-four of the type-II columns were obtained from stained dye patterns. The geometric mean of Ks decreased with increasing column size, i.e., from 2.24, 1.68 to 0.56 cm/h for type-I, -II, and-III columns, respectively. The coefficient of variation (CV) based on a lognormal distribution showed a similar trend: 619% for type-I, 217% for type-II, and 105% for type-III. The percentage of dye stained pattern (macropore cross-sectional area) decreased from 3% at 2.5 cm to 1.7% and 1.6% at 12.5 and 16.5 cm, respectively. Percentage of depth- averaged macropore area was moderately variable with CV = 51%. Weak spatial structure existed for type-I measurements whereas type-II and type-III columns displayed better spatial correlation with a range of approximately 14 m and 11 m, respectively. Cross-semivariogram calculated between type-II Ks values and depth-averaged macropore area indicated spatial dependence. Morphological parameters offer potentials to better predict Ks values when used in soil and water management.