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Aggregate Size Distribution in the Row Zone of Tillage Experiments
Author(s) -
Allmaras R. R.,
Burwell R. E.,
Voorhees W. B.,
Larson W. E.
Publication year - 1965
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/sssaj1965.03615995002900060018x
Subject(s) - tillage , soil science , mathematics , bulk density , logarithm , aggregate (composite) , porosity , soil water , environmental science , agronomy , materials science , composite material , mathematical analysis , biology
A sampling procedure was developed to measure the distribution of soil aggregate diameters in the row zone of row‐cropped corn. At each of 31 locations, 4 preplant tillage treatments were used to obtain different soil conditions in the row zone. Undisturbed soil cores were taken from the 0‐ to 3‐ and 3‐ to 6‐inch layer. Dry aggregate‐diameter distribution and dry bulk density (D B ) were measured for the 0‐ to 3‐inch layer (D B only in the 3‐ to 6‐inch layer). Within 6 weeks after planting D B increased, but the logarithm of geometric mean diameter (log GMD) and the dispersion of aggregate diameters (σ log d ) changed differently depending on tillage treatment and year of study. D B in the 3‐ to 6‐inch layer did not change. Large differences in these measurements were observed among tillage treatments, but within a year of field trials no treatment × location interaction occurred. Some comparisons of measurements were consistent between years and others were not. D B of the 0‐ to 3‐inch layer increased among tillage treatments as σ log d increased, but decreased less as the log GMD increased. A similar relation was shown in the laboratory using mixtures of aggregate‐diameter separates. These changes in D B were mainly due to modification of the interaggregate void space. In the laboratory an increase in weight fraction of water was observed from increasing σ log d . Hence, both log GMD and σ log d are measurable parameters of soil conditions in beds of aggregates, and may help to explain soil water retention and movement, evaporation losses, seed‐soil contact, and root‐soil contact.