PERFORMANCE OF GRAPEVINES UNDER IRRIGATION SYSTEMS - Management, Performance, and Applications of Micro Irrigation Systems - page 259

textural constituents. The soils were subjected to six consecutive cycles of irrigation
with saline waters (SW). Depth distributions of salinity, pH, dispersible clay and hy-
draulic head showed that disaggregation and dispersion of surface soil was the cause
of reduced K in each followed by simulated rain water (SRW), whereas “washed in”
subsoil became restrictive, and controlled the K values with SW under alternations of
SW and SRW. Salt release (<1 meq/L) was insuffi cient to avoid dispersion and sustain
K even in the calcareous soil.
20.1.5.3 SALT DISTRIBUTION
Abd El Razek et al. [4] demonstrated that the maximum salinity was found near the
soil surface at the midpoints between emitters and laterals as well as at the deeper
depths. The 70 cm emitter spacing resulted in a relative reduction in salt content after
irrigation by 5.5 and 10.5% from the original values before irrigation. Ismail et al. [42]
demonstrated that salt distribution varies as a function distance from the dripper and
layer depth under drip irrigation system before and 24 h after irrigation. Hanson and
Bendixen [36] investigated patterns of soil salinity under surface and subsurface trickle
irrigation at water salinity of 2.2 dS/m. High soil salinity occurred midway between
drip laterals for both irrigation methods and above the drip tape for subsurface drip
irrigation. Leaching fractions of 14-26% may be needed under trickle irrigation to
prevent yield reductions of vegetable and fruit crops for irrigation water of EC 2 dS/m.
Minimum leaching fractions are less with lower-salinity irrigation water. Abo-soliman
et al. [3] found a slight decrease in amount of water irrigation values under subsurface
drip system compared to surface drip one. On the other hand the EC values decreased
by about 4 and 11% for subsurface and surface drip systems, respectively.
Chandio et al. [19] stated that soil salinity developed under drip and furrow irriga-
tion methods. Water used was less with the drip method. Soil salinization occurred at
the wetted periphery under drip irrigation. The problem of secondary salinity did not
occur in the furrow-irrigated plots. Hicklenton and Cairns [37] used drip, sub irrigation
and sprinkler irrigated methods. They found that soil EC was highest for subirrigation,
intermediate for drip and pulse irrigation, and lowest for overhead irrigation. It appears
that superior growth of subirrigated plants is due more to better nutrient retention in the
medium than to any effect on plant water status. El-Morsy [26] demonstrated that the
salt distribution was related to the soil moisture distribution. The salt accumulated at
the soil surface and at the boundaries of the wetted zone. The EC values increased in
the surface layer from the source point toward the outer periphery of the wetted zone.
However, the values decreased by going down in the soil profi le from the surface layer
to the bottom one.
Santos and Ribeiro [72] stated that irrigation and cropping affected soil proper-
ties. Chemical properties were differently affected depending upon the management
practices. They added that sites with tree crops and sprinkler or drip irrigation systems
showed increases in the soil pH and exchangeable bases.
20.2 MATERIALS AND METHODS
This study was conducted at the Experimental Farm of Faculty of Agriculture of Ain