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International Journal of Horticulture 2014, Vol.4, No.14, 1
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10
http://ijh.biopublisher.ca
8
growth phases of pepper growth. However, the
reproductive growth fell within periods when the
upper half of the root zone was dry, soil moisture
availability may not be sufficient to meet crop water
requirements. In a situation where upper half of the
root zone was dry and lower half moist, the
development of the root systems (root densities) into
lower half of the root zone will enhance extraction of
soil moisture to meet significant fraction of crop
evapotranspiration. Groundwater contribution is
optimized when roots are fully developed. While the
lower half of the root zone is close to saturation, low
root densities within this half may prevent extraction
of enough moisture to meet potential transpiration
rates (Hurst., 2004: McFadyen & Grieve,2012.).
From the patterns of rooting characteristics of pepper
as affected by irrigation regimes (Figure 5a), it
appears that a large amount of the water that
originated either from irrigation or from ground water
was added to the top zone when the crop was not fully
developed. Therefore this amount might not contribute
much to crop water use. This is supported by the
fact that the average moisture content within crop
root zone was 201 mm while the estimated
evapotranspiration was 164 mm.
In both experiments,
a large amount of water was added to the top of the
root zone before the time the crop was able to use for
dry matter accumulation (the establishment phase of
pepper growth). Actively extracting roots can increase
capillary rise fluxes (Thorburn, 1997), therefore,
guidelines for irrigation requirements in some
situations will be dependent on the rooting depth and
root length density found in the soil profile. Thorburn
(1997) recommended more frequent irrigation events
with small amounts of water during the period when
root length is small. The interval between irrigation
events can be increased when roots have been fully
developed taking advantage of the presence of the
groundwater.
Effects of planting date and irrigation interval on
growth, yield and water Productivity
The effects of planting date and irrigation regimes
were profound on some growth and fruit yield
characters of pepper (Table 3 & 4).
Table 3 Growth and yield characters of pepper grown on residual soil moisture to days to 50% flowering and supplementary
irrigation during reproductive growth phase
Irrigation regimes
Root length
(cm)
Root dry
weight (g)
Shoot dry
weight (g)
Leaf area
(cm
2
)
50% flowering
(days)
Number of fruits
harvested
Fruit yield
(t/ha)
Harvest
index
Weekly
16.3
21.4
129.5
4.68
78
54
9.4
0.54
Fortnightly
19.1
24.5
125.2
3.96
73
48
8.2
0.51
LSD (0.05)
3.0
0.6
2.2
0.04
3.8
3.2
1.6
0.04
Table 4 Growth and yield characters of pepper grown under weekly and fortnight irrigation regimes from planting to crop maturity
Irrigation
regimes
Root length
(cm)
Root
dry
weight (g)
Shoot dry
weight (g)
Leaf area
(cm
2
)
50% flowering
(days)
Fruit yield
(t/ha)
Irrigation
applied
(mm)
Water
productivity
(t/ha/mm)
Harvest
index
Weekly
17.8
67.5
153.2
6.4
72
8.6
59.88
0.048
0.54
Fortnightly 19.3
73.4
140.7
6.0
68
7.9
39.92
0.045
0.50
LSD (0.05) 3.4
4.0
5.1
2.3
4.1
1.8
-
0.004
0.03
Effects of planting date
Fruit yields varied significantly between December and
January sowings (experiments 1 and 2) and irrigation
treatments (Table 5). Differences were obtained in
pepper fruit yields between the December and January
sowings (experiments 1 and 2) across the irrigation
treatments. Total fruit yield was higher in December
(8.8 t ha
-1
) over January (8.5 t ha
-1
) sowing. During the
first sowing (December), the upper half of the root zone
is close to saturation and the short distances between
the root zone and water table would have enhanced the
maintenance of potential transpiration rates under the
near saturated hydraulic conductivities and at low soil
moisture suctions (
-
3 to
-
6 bar).