The content of water-dispersible colloids (WDC) in a soil can have a major impact on soil functions, such as permeability to water and air, and on soil strength, which can impair soil fertility and workability. In addition, the content of WDC in the soil may increase the risk of nutrient loss and of colloid-facilitated transport of strongly sorbing compounds. In the present study, soils from the Bad Lauchstädt long-term static fertilizer experiment with different management histories were investigated to relate basic soil properties to the content of WDC, the content of water-stable aggregates (WSA), and aggregate tensile strength. Our studies were carried out on soils on identical parent material under controlled management conditions, enabling us to study the long-term effects on soil physical properties with few explanatory variables in play. The content of WDC and the amount of WSA were measured at a series of time steps giving a colloid release and aggregate disaggregation rate and a quantification of the content of WDC and WSA at a given time for each of the six investigated experimental field plots. The content of WDC in the moist soil was linearly correlated (r = 0.82* [P < 0.05]) to the part of the total clay not associated with organic matter. No significant difference in release rate was found for air-dry aggregates. The low-carbon soils initially had a higher content of WSA but were more susceptible to disaggregation than the high-carbon soils. Furthermore, the application of NPK fertilizer had a destabilizing effect on the WSA and also caused a decrease in the cation exchange capacity of the soils. The mean tensile strength was positively correlated to the colloid release rate and the content of WDC after 2 min of shaking and therefore to the amount of clay not associated with organic carbon.
1Department of Agroecology, Faculty of Science and Technology, Aarhus University, Tjele, Denmark.
2Department of Biotechnology, Chemistry and Environmental Engineering, Aalborg University, Aalborg, Denmark.
3Department of Plant and Soil Sciences, University of Delaware, Newark, DE.
4Department Community Ecology, Helmholtz Centre for Environmental Research–UFZ, Research Station Bad Lauchstädt, Bad Lauchstädt, Germany.
Address for correspondence: Anders Lindblad Vendelboe, Department of Agroecology, Faculty of Science and Technology, Aarhus University, Blichers Allé 20, PO Box 50, DK-8830 Tjele, Denmark. E-mail: email@example.com
Financial Disclosures/Conflicts of Interest: None reported.
Received May 31, 2011.
Accepted for publication January 23, 2012.