基本HTML版本
International Journal of Horticulture 2014, Vol.4, No.14, 1
-
10
http://ijh.biopublisher.ca
3
also necessary to evaluate the effectiveness of these
systems for crops (vegetable crops) grown in the dry
season on inland valley swaps characterized by
variable but shallow water table depths. The objective
of this study is to examine the value of drip irrigation
schedules for optimizing productivity of water use and
yield of dry season sweet pepper
(Capsicum annuum
L
) grown
in an inland valley swamp in a humid zone
of Nigeria.
Materials and Methods
Experimental layout
Field experiments were conducted on a sandy clay
loam Alfisol to determine the effects of irrigation
scheduling strategies (wet: weekly and dry: fortnight
irrigation intervals) on water use, yield and water
productivity of dry season pepper grown in inland
valley swamp in a rainforest zone of Nigeria. The
experiments were conducted between December 2009
and May, 2010. The sandy loam soil at the site of
study is a tropical rainforest Alfisol classified as
Clayey Skeletal Oxic-Paleustalf (USDA Soil
Taxonomy, 1999). Experiments were conducted
between December 2009 and April, 2010 for which
pepper seedlings were grown on soil water reserve
until peak vegetative growth (date of first flowering)
after which irrigation was imposed during
reproductive growth (flowering to crop maturity), and
between Janaury and May 2010), pepper seedlings
were drip-irrigated weekly and fortnightly from
transplanting to fruit harvest. Pepper seedlings were
grown on the field at 90 by 30 cm spacing and on 10
by 5m field plot per treatment and at three replications
per treatment.
Soil characteristics
The soil at the site of the experiments was sampled
and analysed for physical (textural class, bulk density,
water holding capacity) and chemical (organic matter,
N, P, K Ca, Mg, CEC, electrical conductivity)
properties using standard laboratory procedure. Five
samples were taken within the row and five from the
inter-row spaces in each field. The results of the
analyses are presented in Table 1.
Soil Moisture and Root Studies
Soil moisture was estimated by gravimetric method
and the root observations at harvest were made by
water spray-soil separation method. Core samples
were taken at incremental depths of 10 cm to 60 cm
Table 1 Some physical and chemical properties of soil at site of
experiment
Soil properties
Sand (%)
Silt (%)
Clay(%)
Textural class
Bulk density (g.cm
-3
)
Infiltration rate (mm.s
-1
)
Field capacity moisture (cm
3
.cm
-3
)
1500 KPa moisture (cm
3
.cm
-3
)
Water holding capacity (%)
pH (water)
Organic matter (%)
Total nitrogen (%)
Available P (mg. kg
-1
)
Na (cmol.kg
-1
)
K (cmol.kg
-1
)
Ca (cmol.kg
-1
)
Mg (cmol.kg
-1
)
40
31
29
Sandy clay loam
1.22
347
0.21
0.12
21
6.3
0.96
0.089
16.7
2.37
0.62
4.60
1.37
depth (5 soil samples/10cm depth) while bulk density
was determined for the samples taken at each soil
depth and the values were employed in the conversion
of gravimetric soil moisture contents (oven-dried
moist soil samples at 105
o
C for 24 hours) to
volumetric (cm
3
.cm
-3
). Soil moisture depletion (SWD)
was obtained from the differences in soil moisture
contents (changes in soil moisture contents:(S)
measured between two measurement period. Soil
moisture contents were determined weekly at
incremental depths of 20 cm of soil and was taken
with augers and core samplers.. Soil water pressure
heads was measured using tensiometers installed at 20
and 60 cm below soil surface at 10 cm away from
pepper plants. 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. From
the experimental field, ten points were sampled
weekly starting from transplanting to crop
physiological maturity. Five samples were taken
within the row and five from the inter-row spaces in
each field. Average daily temperature was used to
calculate thermal time (TT) for each day; TT (is daily
temperature from emergence, E to date of first
flowering, HV multiplied by the number of days from
E to HV). Cardinal temperatures, namely base