Agriculture Reference
In-Depth Information
Aggregates in the size range 2-20 ECD may be large floccules or tactoids.
However‚ the majority probably comprise associations of clays and microbial remnants.
Figure I.11a shows orientated clay particles associated with such microbial structures as
bacteria‚ fungal hyphae and plant roots. The clay particles and tactoids are bound to
the substantial quantities of polysaccharides produced by these organisms (Figure I.11b).
In the size range 20-250 ECD‚ aggregates are stable to rapid wetting but less so
than those in the range 2-20 ECD. Materials bonding clay in particles of the size
range 20-250 ECD include persistent organic matter‚ oxides of iron and aluminium
and highly-disordered silicate clay minerals; the additive effects of these bonding agents
produce strong‚ water-stable aggregates.
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