Author:
Balks M. R.,Bond W. J.,Smith C. J.
Abstract
Effluent irrigation commonly results in increased soil sodicity, because of
the medium-to-high salinity and high sodium concentrations of many effluents.
The exchangeable sodium percentage (ESP) of soils at the Wagga Wagga Effluent
Plantation Project increased from <2% to >25% at some
depths within the surface 0·6 m of soil, after 5 seasons of irrigation
with either (i) treated sewage effluent or
(ii) bore water with similar salinity and sodium
adsorption ratio (SAR). A survey of dispersion index (DI) and saturated
hydraulic conductivity (Ksat) was
carried out to investigate the effects of increased soil sodicity on soil
physical properties. The Ksat was
measured after 5 irrigation seasons at 2 depth intervals
(0·15-0·45 m and 0·5-0·8 m) using both bore water
and distilled water, and compared with measurements made at the same sites
using bore water before irrigation commenced. Both DI and ESP were measured at
each of 3 depths in the surface 0·6 m of soil. The DI in distilled
water was positively correlated with ESP, with finer soil textures having
higher DI for the same ESP. When measured in bore water or effluent, DI was
very low and not related to ESP.
Ksat was significantly lower after
5 irrigation seasons, and significantly lower in distilled water than in bore
water. However, there was no relationship between
Ksat and ESP. It was concluded
that the increased ESP caused an increased tendency for soil dispersion but
was not shown unequivocally to lead to decreased
Ksat. The increased sodicity does
not seem likely to affect continued use of the land for effluent irrigation,
but may affect its suitability for alternative uses that involve physical
disturbance of the soil, for example, by cultivation.
Subject
Earth-Surface Processes,Soil Science,Environmental Science (miscellaneous)
Cited by
65 articles.
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