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Effect of irrigation with olive mill wastewater on soil hydraulic and solute transport properties
Mohawesh, O.; Mahmoud, M.; Janssen, M. & Lennartz, B.
Abstract
To evaluate the effect of olive mill wastewater
(OMW) application on soil hydraulic and transport properties,
two treatment sites, which had been irrigated with
OMW for 5 and 15 years, and one control site being irrigated
with freshwater were compared. The transport and
leaching experiment results showed that a portion of the
total soil water was available for transport processes while
the remaining of the soil water was considered immobile
and not readily accessible for solutes. The separation in
water fractions of different mobilities was surprisingly
consistent among OMW treatments. The bromide recovery
rate decreased with the application of OMW showing that
tracer molecules became trapped within immobile water
phases. The application of OMW increased significantly
the soil water-holding capacity, whereas the soil hydraulic
conductivity in the near saturation range decreased significantly
with long-term OMW application. The soil irrigated
with OMW had significantly higher organic matter content,
lower bulk density and relatively higher total porosity, but
lower macroporosity than that of control sites. We concluded
that the soil was increasingly coated with complex
organic molecules originating from OMW, as a result,
solute exchange between inter- and intrasoil aggregate
water was hindered. Although OMW could cause soil and
water pollution, its use in agriculture is promoted because
of high nutrients and organic matter contents.
Keywords
Breakthrough curves; Hydraulic conductivity; Mobile-immobile soil water; Soil water retention; Soil and water pollution
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