PERFORMANCE OF GRAPEVINES UNDER IRRIGATION SYSTEMS - Management, Performance, and Applications of Micro Irrigation Systems - page 258

conductivity of the subsoil. Norris and Tennessee [66] indicated that lateral movement
is enhanced if the soil is stratified, the initial soil moisture is low, and the application
rate is low. They also observed that at high moisture tension (low moisture content)
lateral movement was more pronounced in finer soil layers than in coarser layers. El-
Gindy [25] reported that the moisture content of the top soil (0-20 cm) was higher in
the drip-irrigated field than those of surface, and sprinkler systems. Meanwhile the
lowest moisture content in the same layer was in the surface irrigated field. Hanafy
[35] indicated that the major fluctuations in soil water tension occurred in the top 30
cm of the soil profile. This is mainly due to that most crops moisture withdrawal from
the soil is near the surface where more roots are normally growing.
20.1.5.2 SOILINFILTRATION RATE
Mousavi et al. [62] stated that infiltration is an important physical property of soil
affecting irrigation. Lodge and Baker [56] stated that soil physical properties of three
types of golf green construction in the UK, were a sandy loam top soil with pipe drain-
age and two suspended water table constructions, one with a root zone of pure sand,
the other with a root zone conforming to the US Golf association specifications. The
irrigation treatments represented replacement of 75, 100 and 125% of evapotranspira-
tion losses in 1990 and 60, 100, and 140% of losses in 1992. Soil pore structure of
the sand-based root zone changed slowly over time. Infiltration rates fell significantly
over time. Infiltration rates on the sand-based root zones were greater at higher rate of
nitrogen fertilizer application (410 kg ha -1 per year) than the lower rate (110 kg ha -1
per year). The soil constructions showed a reduction in the proportion of pore spaces in
the top 10-90 mm of the profile, probably due to compaction process. Infiltration rates
were consistently very low, but increased for a short period following the application of
a 'Verti-Drain' treatment. Yapa [85] stated that in the 'very rapid' and 'rapid' infiltration
categories, the drainage problems are unlikely, so it is recommended to use overhead
irrigation methods for high water use efficiency (WUE).
Wang et al. [82] mentioned that the time required to infi ltrate a prescribed amount
of water or chemical increased from sprinkler to furrow to drip irrigation. Furrow
irrigation leached the chemical more rapidly than either drip or sprinkler irrigation.
Sprinkler irrigation was less susceptible to cause ground-water contamination than
furrow or drip irrigation. They added that the interactive effect of irrigation methods
and spatial variability of saturated hydraulic conductivity (Ks) was determined with
the combined use of a two-dimensional deterministic solute transport model and a
stochastic parameter generator. In a homogeneous Ks fi eld, the time required to infi l-
trate a prescribed amount of water or chemical increased from sprinkler to furrow to
drip irrigation. Furrow irrigation leached the chemical more rapidly than either drip or
sprinkler irrigation. Assuming the spatial distribution of Ks to be a stationary stochastic
process, increased spatial variability in Ks reduced the infi ltration rate. When Ks was
spatially correlated, sprinkler irrigation was less susceptible to cause groundwater con-
tamination than furrow or drip irrigation. The concentration distributions in the uncor-
related Ks fi eld were not very different from those in the homogeneous fi eld.
Minhas et al. [59] monitored the hydraulic conductivity (K) and related soil prop-