الفهرس 
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Abstract
The problem of non-equilibrium and/or preferential flow and transport has received
much attention in the soil and agricultural sciences because of its implications in
accelerating the movement of agricultural contaminants (fertilizers, pesticides, pathogenic
microorganisms and toxic trace elements) through the unsaturated zone (vadose zone) to
underlying groundwater.
Non-equilibrium flow and transport are probably the most difficult processes in
terms of restrain accurate predictions of contaminant transport in soils and fractured rocks.
Non-equilibrium or/and preferential flow, as opposed to uniform flow, results in irregular
wetting of the soil profile as a direct consequence of water moving faster in certain parts of
the soil profile than in others.
There is good confirmation by many investigators that water flow and solute
transport processes in soil often cannot be described using classical models that assume
uniform flow and transport. Many experiments (laboratory or field experiments) have
illustrated the presence of non-equilibrium flow and transport conditions in soil. Attempts
to describe non-equilibrium transport have traditionally developed along two lines:
physical and chemical non-equilibrium models. Physical non-equilibrium models assume
that non-equilibrium flow or transport is caused by physical factors such as soil
heterogeneity. Chemical non-equilibrium models assume that chemical factors are the
cause of non-equilibrium transport. Few researchers have been combined the physical and
chemical non-equilibrium approaches to account both possible causes of non-equilibrium,
thus we can improve the description of water flow and solute transport in soil. Over the
years, several numerical models have been developed to consider number of options for
simulating non-equilibrium water flow and solute transport processes.
The most common model is HYDRUS-1D software package (Šimůnek et al.,
2005, 2008), it is wide range approaches that can be selected for simulating nonequilibrium
processes. The HYDRUS software packages are among the most widely used
models simulating water flow and solute transport in soils. Traditionally, the HYDRUS
software, as well as many other models simulating variably saturated water flow and solute
transport. The objectives of the present work were to evaluate and compare the physical
and chemical non-equilibrium processes of potassium transport under the present
experimental conditions using the last version of HYDRUD-1D (Šimůnek et al., 2008.