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Soil and Tillage Effects on the Characteristic Size and Shape of Aggregates
Author(s) -
Perfect E.,
Zhai Q.,
Blevins R. L.
Publication year - 1997
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/sssaj1997.03615995006100050025x
Subject(s) - loam , tillage , fraction (chemistry) , mathematics , silt , soil science , chemistry , mineralogy , agronomy , geology , soil water , chromatography , biology , geomorphology
Abstract Measures of aggregate size and shape are needed in models to predict soil erosion, seed bed density, tensile strength, and solute diffusion. We hypothesized that size (i.e., equivalent cubic length L c = [ l 1 ( l 2 l √2)( l 3 l √3)] 1/3 , where l 1 , l 2 , and l 3 are the shortest, intermediate, and longest axial lengths, respectively) and shape (i.e., aspect ratios, l 1 / l 3 and l 2 / l 3 ) vary with soil type and tillage treatment. Caliper measurements of l 1 , l 2 , and l 3 were made on 1800 aggregates from three sieved fractions (4–8, 8–16, and 16–31.5 mm) of a plowed, plowed plus disked, and no‐till Maury silt loam (fine, mixed, mesic Typic Paleudalf) and a no‐till Karnak silty clay (fine, montmorillonitic, nonacid, mesic Vertic Haplaquept). Overall means for l 1 / l 3 (0.57) and l 2 / l 3 (0.78) were close to those for a cube (0.58 and 0.82, respectively). The mean l 1 / l 3 for Karnak was 18% lower than the corresponding value for no‐till Maury. The L c was lognormally distributed. The mean log 10 ( L c ) increased from 0.67 in the smallest fraction to 1.19 in the largest fraction. Soil effects on log 10 ( L c ) were most evident in the 8‐ to 16‐mm fraction (1.01 for Karnak compared with 0.93 for no‐till Maury). Tillage effects on log 10 ( L c ) were most evident in the 4‐ to 8‐mm fraction (0.68 for no‐till Maury compared with 0.66 and 0.65 for plowed and plowed plus disked Maury, respectively). The equation L c = x l ( m/m m ) 1/3 , where x l is lower sieve aperture, m is aggregate mass, and m m is modal mass, explained 96% of the variation in L c . This equation can be used to predict aggregate size from sieve aperture size and measurements of aggregate mass.