Effects of Soluble Salts on Water Holding Capacity of Hydrophilic Polymers: A Case Study on Geohumus

Publikations-Art

Kongressbeitrag

Autoren

Duong, V.N., Asch, F.

Erscheinungsjahr

2011

Veröffentlicht in

Development on the margin

Herausgeber

Becker, M. et al.

Verlag

Cuvillier Verlag , Göttingen

Seite (von - bis)

512

Tagungsname

Tropentag 2011

Tagungsort

Bonn

Gel-forming polymers that can absorb water up to 1000 times their weight are considered
as ameliorants of soil water supply in arid and semi arid areas. A new product belonging
to these polymers, called Geohumus, can absorb pure water up to 40 times of its weight.
However, when Geohumus is applied under field conditions, soil physical condition and the
ion concentration of soil water may interfere with this water absorption capacity. In order
to quantify these effects Geohumus was imbedded in variable concentrations and types
of salts, a standard nutrient solution as well as soil extracts for 2 hours and the water
absorption quantified. Significant differences in water holding capacity (WHC, g of water
per g of Geohumus) between treatments were noticed with all treatments lowering the
WHC compared to that measured in distilled water (13.5 g H2O g−1), sandy soil extract
(8.2 g H2O g−1) and sandy soil extract with nutrient solution (4.4 g H2O g−1). Testing
the WHC over a wider range of salt concentrations i.e., 0.01 to 0.05M, WHC of Geohumus
decreased in the order: KNO3, NH4NO3, NaCl, K2SO4, MgSO4, Al2O12S3·13.4–14.5H2O,
and FeSO4·7H2O. WHC and concentration of salts were negatively correlated. Valance II
elements impeded Geohumus water absorption capacity more than valances I elements. In
conclusion, similar to other hydrophilic polymers, WHC of Geohumus is sensitive external
salt concentrations which are realistic for in-situ soil solutions. These results imply that
when Geohumus is applied under field conditions interactions between soil type and soil
solution composition should be considered.