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Macroporosity and Its Relation to Saturated Hydraulic Conductivity under Different Tillage Practices
Author(s) -
Logsdon S. D.,
Allmaras R. R.,
Wu L.,
Swan J. B.,
Randall G. W.
Publication year - 1990
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1990.03615995005400040029x
Subject(s) - macropore , loam , hydraulic conductivity , tillage , subsoil , soil science , infiltration (hvac) , conventional tillage , geology , mineralogy , hydrology (agriculture) , environmental science , soil water , materials science , chemistry , composite material , geotechnical engineering , agronomy , mesoporous material , biochemistry , biology , catalysis
Tillage management influences the distribution of macropores (biopores, cracks, interpedal planes, and packing voids) that may provide pathways for rapid infiltration of water. To aid in predicting ranges of saturated hydraulic conductivity ( K sat ), macropore distribution in situ was characterized by exposing selected horizontal planes and tracing macropores on clear polyethylene sheets. A methylene blue solution was used to indicate macropore continuity through the pressure pan. Sixteen undisturbed cores were taken in a grid pattern from each Ap horizon and adjacent subsoil for determination of K sat . Field marking on plastic sheets was superior to photographic slides as a technique to characterize macropores because film noise (false pores) was eliminated, overall analysis time was reduced, and different features could be separated for analysis. Unfortunately, a bias of pore size between observers was possible. Four sites with four different soil series were examined: Nicollet (fine‐loamy, mixed, mesic Aquic Hapludoll), Rozetta (fine‐silty, mixed, mesic Typic Hapludalf), Waukegan (fine‐silty over sandy or sandy‐skeletal, mixed, mesic Typic Hapludoll), and Normania (fine‐loamy, mixed, mesic Aquic Haplustoll). Below the maximum tillage depth, macropores were present at all locations, but tillage disrupted continuity of pores from the surface. No‐till had macropores throughout the upper 70 cm with continuity observed in the 0‐ to 35‐cm range. Numbers of pores (>0.4‐mm diam.) per m 2 ranged from 100 to >3000, representing 0.1 to 2% of the total area. When present, horizontal crack length ranged from 1.7 to 19.3 m m −2 . Measured K sat on undisturbed detached cores ranged from 1.1 to 180 µm s −1 with CVs ranging from 44 to 197%. The K sat could be estimated within a range (out of eight classes) from descriptions of biopore area, cracks, soil structure, and soil texture.