Dispersion of saline and non-saline natric mollisols and alfisols
2004
Ward, Phillip A. III | Carter, Brian J.
Roadway and building construction, crop and forage production, and land reclamation all benefit from reliable identification and delineation of dispersed soil. Improved understanding of dispersed soil also leads to better treatment practices. The dispersion of 103 horizons from natric soils ranges from 0 to 96%, with comparisons of 31 non-to-weakly-dispersed (<30% dispersion by the double hydrometer method), 30 moderately dispersed (30 to 65% dispersion), and 42 strongly dispersed (>65% dispersion) horizons indicating multiple influences on dispersion. The amount of dispersion in soils depends on several soil properties, including sodium adsorption ratio (SAR), electrical conductivity (EC), pH, bulk density (gcc), clay-sized particles (mg kg), organic matter (mg kg), ratio of charge of chloride ions to charge of sulfate ions in soil water, and ratio of charge of sodium ions to the sum of the charges of sodium and calcium ions in soil water. Dispersion increases with illite content in the clay fraction of the soils. Critical SAR values for identification of dispersed soil calculated from EC and percent dispersion data are 4.4 ± 0.2 for weakly saline (EC < 1 dS m) and 8.0 ± 0.8 for moderately saline (EC from 1 to 9 dS m) soils. Mean and median SAR values of the strongly saline horizons (EC>9 dS m) in the study are 48.3 ± 24.0 (1 Std. Dev.) and 51.7, respectively. Critical SAR values identified are alternatives to existing diagnostic values for identification and management of dispersed soil in semiarid and subhumid regions.
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