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International Journal of Horticulture 2014, Vol.4, No.14, 1
-
10
http://ijh.biopublisher.ca
4
temperature (T
b
8
℃
), optimum temperature (T
opt
32
℃
), and maximum temperature (T
max
42
℃
) (Agele.,
2002), were assumed in the calculation of heat unit
accumulation.
Pepper growth and fruit yield
Data were collected on pattern of soil moisture storage
and depletion, and agronomic parameters of root and
shoot biomass, leaf area and fruit yield characters of
pepper. Agronomic characters of root and shoot
biomass, leaf area, fruit yield and yield components
were monitored from ten plants per plot randomly
sampled from 2 m
2
at the center of each plot. Root and
shoot biomass were oven-dried at 80
o
C for 48 h and
dry weights were recorded. The depth of the effective
root zone was estimated after full cover by excavating
the root system of different plants. The depth of the
effective root zone was found to be around 60 cm
(Agele., 2002). Pepper plant leaf area was measured at
50% flowering date using a leaf area meter (Delta T,
UK). Pepper fruits were harvested weekly from ten
plants sampled per plot starting from physiological
maturity. Harvested fruits per plant were counted and
summed over all fruit harvests while mean fruit
weight per plant was computed from the average of
ten sample weights of fruits.
Irrigation strategies
In the first experiment (first planting: December,
2009), adequacy of soil moisture from planting to date
of first flowering was assumed (growth stage
scheduling plus regulated/deficit irrigation). Pepper
seedlings were therefore grown on residual soil water
(soil water reserve) until peak vegetative growth (date
of first flowering; 2 to 7 Weeks after transplanting,
WAT). Thereafter irrigation was imposed during
reproductive growth (flowering to crop maturity: 8 to
16 WAT). In another set, second planting (Janaury,
2010), pepper seedlings were drip-irrigated weekly
and fortnightly from transplanting to fruit harvest. For
both experiments, irrigation regimes consisted of
water application weekly and fortnight intervals using
gravity-drip irrigation system and 1.38 litres of water
per plant at each irrigation via point source emitters of
2l/h discharge rate which were installed on laterals per
row of crop. The emitters were installed on laterals per
row of crop and were spaced 1 x 1 m apart. Irrigation
buckets were suspended on 1 – 1.5 m high stakes to
provide the required hydraulic heads. Irrigation
buckets were suspended on 1 – 1.5 m (hydraulic heads)
high stakes (IWMI, 2002; Olufayo, personal
communication). Table 2 presents the various growth
phases of pepper. For the high to low irrigation
regimes soil moisture storage ranged from 100 to
50 % of plant available water. There was two-day
pre-irrigation treatment (4.8 mm/plant/day) following
pepper seedling transplanting, and thereafter, the
weekly and fortnight irrigation treatments were
imposed.
Table 2 Soil moisture management strategies for dry season
grown-pepper in an inland swamp: growth on residual moisture
from planting to days to 50% flowering and supplementary
irrigation at reproductive growth, and irrigated crop from
transplanting to crop maturity
Growth stages and time- scale in Experiment 1 (residual
moisture plus supplementary irrigation at flowering)
Establishment/Development (2-5 wks) Dec-Jan
Mid season/flowering (5-9 wks) Jan-Feb
Fruiting (9-14 wks) Feb-Apr
Fruit harvest (14 - 18 wks) Apr-May
Growth stages and time- scale in Experiment 2 (Weekly and
fortnight irrigation regimes from planting to maturity)
Establishment/Development (2-5 wks) Jan-Feb
Mid season/flowering (5-9 wks) Feb-Mar
Fruiting (9-14 wks) Mar-Apr
Fruit harvest (14 -18 wks) Apr-May
At weekly interval, soil moisture content was
determined using the gravimetric method (5 soil
samples/10cm depth) and via tensiometers placed for
measurements of the hydraulic gradient. Each of the
main plots had tensiometers placed at 20 and 60 cm
depth for the daily measurement of the hydraulic
gradient. The tensiometers placed at soil depths were
to indicate the downward water movement following
irrigation or if otherwise the hydraulic gradient was
reversed.
Peak evapotranspiration (ET
peak
) rate for the crop
under drip irrigation treatment was estimated as:
ET
peak
= ETo*P/85……………7
where ET
peak
is peak evapotranspiration rate for
the month or period, ETo is the reference
evapotranspiration, for the month/period (e.g. 5.1 mm/
day), P is the proportion of total land area covered by
the crop leaf area (cm) which is assumed 80% (after
Agele, 1999; Agele., 2011).