Long-term Iysimeter experiments were conducted at Sakha Agric. Res. SI.
during twelve successive growing seasons started in summer season 1997 to summer
season 2003. The aim of this study was to evaluate the effect of irrigation water
quality (fresh, treated sewage water and drainage water) on some soil hydrophysical
properties of four soils (clay, loamy, sandy and calcareous) with drip irrigation system.
The main results could be summarized as follows: The highest values of soil moisture content at different tensions, quickly, slowly
and total d rainable pores, water holding pores, soil hydraulic conductivity and total
porosity as well as t he lowest values 0 f fine capillary pores and bulk density were
achieved with irrigation by treated sewage water in clay and loamy soils. In sandy and
calcareous soils the values of quickly, slowly and total drainable pores were
decreased, while the water holding pores and fine capillary pores were increased due
to irrigation with treated sewage water. The high clay content of soil led to increase the soil moisture content, water
holding pores, fine capillary pores and total porosity meanwhile soil moisture retention
curves were gradually sloped. But the values 0 f quickly, s lowly a nd total drainable
pores, hydraulic conductivity and bulk density were decreased. On the other hand, the high content of sand fractions decreased the soil
moisture content, slowly drainable pores water holding pores, fine capillary pores and
total porosity, therefore, soil moisture retention curves were very sharply sloped. But
the quickly and total drainable pores, hydraulic conductivity and bulk density values
were increased. The data indicated that the soil moisture content at different tensions, slowly
drainable pores, water holding pores, fine capillary pores and total porosity were
highly significantly positively correlated with clay and organic matter contents and EC
of soil, but highly negatively with coarse sand. While quickly and total drainable pores,
hydraulic conductivity and bulk density are highly significantly positively correlated
with coarse sand but highly significantly negatively correlated with clay and organic
matter contents and EC of soil. It could be conc!uded that the long term irrigation by treated sewage water
improved the soil hydrophysical properties, especially in sandy and calcareous soils.