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| Titel |
Aggregates and structure stability as affected by polymer application and aggregate size |
| VerfasserIn |
Amrakh I. Mamedov, Guy J. Levy |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250087419
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| Publikation (Nr.) |
 EGU/EGU2014-1466.pdf |
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| Zusammenfassung |
| Studying the effects of amendments application on soil structure is important for the
development of effective soil and water conservation and management practices. The
contribution of polymer addition to soil-structure stability depends, among others, on soil
aggregate size which may vary with changes in soil properties and management. The
effects of aggregate size (0.25-0.5; 0.5-1.0; 1.0-2.0 mm) of four semi-arid soils
of varying texture (loam, sandy clay, and two clays), addition of 100 mg L-1 of
high-molecular-weight polyacrylamide (PAM) and rate of aggregate wetting (2
and 100 mm h-1) on aggregate and structure stability were studied using the high
energy moisture characteristic (HEMC) method and deionized water. In this method,
energy of hydration and entrapped air are the main forces responsible for breaking
down of the aggregates. Differences in aggregate and structure stability among
treatments were inferred from changes in water retention curves obtained at low suction
(Ψ ≥-5.0 J kg-1) which were, quantified using the modified van Genuchten (1980)
model. Products of the water retention curves analysis by the model include (i) the
parameter α which represent the location of the inflection point that can also be
considered as the most frequent pore size termed modal suction (MS; MS=1/ α), (ii) the
parameter n which indicates the steepness of the S-shaped water retention curve
respectively, and (iii) the volume of drainable pores (VDP), which is an indicator
for the quantity of water released by the tested sample over the range of suction
studied. The change in the above indices is considered to be related to changes
in pore-size distribution, and therefore to changes in aggregate and particle size
distribution, thus characterizing the contribution of the management or treatments
to aggregates stability. Our main findings indicated that (i) the tested treatments
significantly affected the shape (e.g., α and n) of the water retention curves, (ii) soil
type, aggregate size, PAM application and wetting rate and their interactions had
significant effects on the stability indices, (iii) addition of PAM had no or small effect
on the stability of small aggregates (0.25-0.5 mm), but significantly increased the
stability of the larger aggregates (0.5-1.0 and 1.0-2.0 mm) and (iv) PAM-treated
aggregates retained more water at low suction Ψ ≥-1.2 J kg-1, and were less
affected by rate of water addition than untreated aggregates. Our results suggest that
effectiveness of PAM application in stabilizing aggregates and soil structure against water
cannot be straightforwardly predicted as it strongly depends on soil properties and
conditions prevailing in the field (e.g., texture, aggregate size and rate of water addition). |
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