Soil physical properties related to soil structure

Amsterdam

1994

187-216

Sonderdruck

12269S

202838

The aim of this paper is to clarify the effect of soil aggregation on soil physical and chemical properties of structured soils both on a bulk soil scale, for single aggregates, as well as for homogenized material. Aggregate formation and aggregate strength depend on swelling and shrinkage processes and on biological activity and kinds of organic exudates as well as on the intensity, number and time of swelling and drying events. Such aggregates are, most of all, more dense than the aggregated bulk soil. The intra-aggregate pore distribution consists not only of finer pores but these are also more tortuous. Thus, water fluxes in aggregated soils are mostly multidimensional and the corresponding water fluxes in the intra-aggregate pore system are much smaller. Furthermore, ion transport by mass flow as well as by diffusion are delayed, whereby the length of the flow path in such tortuous finer pores further retards chemical exchange processes. The chemical composition of the percolating soil solution differs even more from that of the corresponding homogenized material the stronger and denser the aggregates are.Keywords: Aggregate formation; Soil structure; Hydraulic process; Chemical property; Soil aeration; Mechanical effectSchlüsselwörter: Aggregatbildung; Bodenstruktur; Hydraulischer Prozess; Chemische Eigenschaft; Bodenbelüftung; Mechanischer Effekt