Industrial Crops and Products 11 2000 163 – 172
Growth and yields of kenaf varieties in central Greece
E. Alexopoulou , M. Christou, M. Mardikis, A. Chatziathanassiou
Center for Renewable Energy Sources,
19
th km Marathonos A6e.,
19009
, Pikermi, Attiki, Greece Accepted 8 October 1999
Abstract
Kenaf is a rapidly growing crop of great interest as a source of low cost natural fiber. Kenaf fibers can be used in the manufacture for a wide range of pulp, paper and paperboard products and may be a substitute for fiberglass and
other synthetic fibers. The purpose of this work was to study the adaptability, growth and yields of three early PI 3234923, PI 318723 and PI 248901 and four late-maturity kenaf varieties Everglades 41, Everglades 71, Tainung 2
and JT1 in central Greece. In a period of 3 years 1994, 1995 and 1997, three kenaf field trials were conducted in two fertile sites Kopais and Aliartos in central Greece. In the first experiment 1994, the density of the trial was
240 000 plantsha, while in the second 1995 two plant populations were tested 320 000 and 170 000 plantsha. Due to the fact that in 1995 the higher plant population 320 000 plantsha resulted in higher yields, the following trial
of 1997 was decided to be designed only for the high plant density. Data collected in all experimental fields included canopy height, leaf area index LAI, basal stem diameter, fresh and dry yields and yields components. In contrast
with the early-maturity varieties, the late-maturity ones resulted in higher values for all the tested parameters. In all trials, this superiority was statistically significant LSD Test, P = 0.05 from early August until the end of the growing
period. Early varieties exhibited 33.34 tha fresh biomass yields PI 248901, 1997 and late varieties 88.66 tha Tainung 2, 1994. The corresponding values for dry matter yields varied from 9.40 tha PI 318723, 1997 to 23.95
tha Tainung 2, 1994. Between the two plant populations, the high 320 000 plantsha was more productive than the low one 170 000 plantsha, but this difference was statistically significant only until the flowering phase. © 2000
Elsevier Science B.V. All rights reserved.
Keywords
:
Adaptability; Growth; Late and early-maturity kenaf varieties; Yield; Yield components www.elsevier.comlocateindcrop
1. Introduction
Kenaf Hibiscus cannabinus L. is a rapidly growing crop of great interest as a source of low
cost natural fiber and feedstock for energy pro- duction as well. Kenaf fibers can be used in the
manufacture for a wide range of pulp, paper and paperboard products and may be a substitute for
fiberglass and other synthetic fibers. As fibrous crop, kenaf appears to have enormous potential
to become a valuable biomass crop of the future.
When it is cultivated in high plant population, it has an erect stem consisting of an inner core of
short woody fibres 0.5 – 1 mm long and an exter-
Corresponding author. Tel.: + 30-1-6039900; fax: + 30-1- 6038006.
E-mail address
:
ealexcres.gr E. Alexopoulou 0926-669000 - see front matter © 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 9 2 6 - 6 6 9 0 9 9 0 0 0 6 4 - 3
Table 1 Site coordinates of the field trials
Site Aliartos
Kopais 38°.22
38°.23 Latitude
23°.10 Longitude
23°.06 114 m
110 m Altitude
number of kenaf varieties early and late in two fertile sites of central Greece. The tested varieties
have been selected for their high yielding potential in relative trials worldwide.
2. Material and methods
2
.
1
. Experimental sites In a period of three years 1994, 1995 and 1997
three kenaf experimental fields were established in two fertile sites Kopais and Aliartos in central
Greece. In the first and second year, the experi- ments were conducted in Kopais and in the third
year in Aliartos.
Kopais is located in a large plain of about 20 ha, derived from the drainage of lake Kopais.
Kopais field is characterized by a very fertile soil with high percentage of organic matter Table 2.
Due to a high underground water table from late spring to early summer, soil moisture content
approached saturation level during the early growth stage.
Aliartos Forest Service Nursery of Aliartos is situated 7 km away from the Kopais field. It
should be noted that Aliartos field was located at the bank of lake Kopais. Although the two sites
were located in short distance Table 1, the soil texture was greatly differentiated Table 2.
In Kopais field, the previous crops were cereals and corn that were cultivated in rotation for a
number of years. On the contrary, Aliartos was left fallow from 1978.
The climate in both sites is characterized as continental with large temperature variations be-
nal bark with fibres 3 – 4 mm long. The bark fibres are comparable to soft woody fibres, while the
inner short, woody fibres of the core are compara- ble to hardwood fibres Francois et al., 1992. The
paper produced from paper pulp has excellent ink-retention characteristics and its high tensile
strength is ideal for high-speed presses Robinson, 1988.
Flowering of late-maturity kenaf varieties is under photoperiodic control and plants remain
vegetative until daylight falls below 12 h and 45 min. On the contrary, photoperiodic does not
influence the flowering of the early-maturity kenaf varieties.
A great number of varieties late and early have been tested under various environments and
cultivation methods worldwide. It is reported that most of the late-maturity varieties resulted in
higher yields compared to the early ones Petrini et al., 1994.
High plant populations have been reported to exhibit higher fresh and dry matter yields Higgins
and White, 1970; White et al., 1971; Muchow, 1979; Bhangoo et al., 1986; Kipriotis et al., 1998.
Due to the limited information referring to kenaf cultivation in Greece, this work aimed at
testing the adaptability, growth and yields for a
Table 2 Soil characteristics of the field trials
Site Kopais
Aliartos Soil layers
0-40 cm humic layer, 40–80 cm marl, 0–58 cm SC, 58–82 cm CL, 82–92 cm S,
92–110 cm S, 110+ cm S 80+cm sand
0.536
a
Organic matter 4.5
a
95.30
a
Electrical conductivity 39.19
a
mmhoscm PH
8.00
a
7.98
a a
The values correspond to the first soil layer for each site.
Fig. 1. Monthly max and min air temperatures for the years 1994, 1995 and 1997.
Fig. 2. Monthly rainfall for the years 1994, 1995 and 1997.
tween day and night and strong winds. The high air temperatures that occurred in the experimental
sites from late May to late September in relation to the low rainfalls made irrigation necessary for
covering the crop needs Figs. 1 and 2.
Irrigation was applied by the drip method and the pipes of the drip system were also used for
nitrogen fertilization.
2
.
2
. Experimental layouts In 1994, a preliminary experimental field was
established in Kopais, in order to examine the adaptability of the crop in central Greece. Five
varieties were sown on May 25. PI 3234923 was an early-maturity variety, while Everglades 41,
Everglades 71, Tainung 2 and JT1 were late-matu-
rity varieties. The density of the trial was 240 000 plantsha. In the course of the growing period, the
plants received 333 mm of water in total, except for the rainfalls. When the plants were 40 cm
high, a quantity of 75 Kg Nha was applied through the drip irrigation system.
In the following year, a more complicated trial was carried out next to the previous one Table
3. Based on the results obtained from the previ- ous trial, it was decided plant population to be
studied as a factor in addition to variety. On May 31, 1995, three early varieties PI 3234923, PI
248901 and PI 318723 and two late Everglades 71 and JT1 were sown in two plant populations
320 000 and 170 000 plantsha Table 3. Except for the rainfalls, 329 mm of water was applied
from late May to late September. At the early stages of growth, nitrogen fertilization 50 Kg
Nha was applied through the drip irrigation system.
A third experimental field was conducted in 1997 at Aliartos and five varieties PI 3234923, PI
248901, Everglades 41, Everglades 71 and Tain- ung 2 were sown on June 2 Table 3. The first
two were early and the latter three were late-ma- turity varieties. Based on the high yields that were
recorded
in 1995,
in the
plots with
the higher plant population 320 000 plantsha, the
same high plant population decided to be used only in this trial. All plots received 355 mm of
water and 75 Kg Nha of nitrogen fertilization. The experimental layouts, the under study factors
as well as the plot size for all trials are presented in Table 3. Trials were kept weed free by hand
hoeing.
2
.
3
. Measurements In the course of each field trial, canopy height
was regularly measured and growth rate was estimated.
In order to estimate fresh and dry yields and yields components several harvests were carried
out during all years. Harvests started in late July and continued until the end of December. In each
harvest date a one-meter row 0.7 m
2
was har- vested and the leaves were separated from the
stems. Sub-samples from each fraction were taken for LAI and dry matter determination. Leaf area
was calculated with a Leaf Area Meter. Dry mat- ter in stems and leaves was evaluated after drying
the samples at 85°C at constant weight. More- over, a harvest of a larger area 8.4 m
2
was accomplished from late October to early Novem-
ber in each site. At that time the early varieties were at the stage of seed maturity, while the late
varieties were at the end of the flowering phase. Because of the quite high moisture content at that
time, a couple of harvests were accomplished later in the season until the end of the year, in order to
estimate the most appropriate harvesting time for energy purposes.
Basal stem diameter was measured in each trial at the end of the growing season. At the end of
the growing season in the 1994 field trial, bark was separated from the core and fresh and dry
stem components bark and core were estimated on fresh and dry matter basis and barkcore ratio
as well.
The effect of the tested varieties on yields was tested
by a
standard analysis
of variance
ANOVA. The effect of variety, plant population
Table 3 Experimental layouts and factors of the field trials
Treatments Year
Plot size
a
Experimental layout Randomized complete block in
6×4.5 m
2
, 20 plots, PI 3234923, Everglades 41, Everglades 71,
1994 Tainung 2, JT1
three replications 6 rows per plot
PI 3234923, PI 248901, PI 318723, Ever- 6×4.5 m, 20 plots,
1995 A randomized complete block factorial 2
2
in 6 rows per plot
glades 71, JT1, 320 000 plha, 170 000 plha two replications
Randomized complete block in 6×5 m, 15 plots,
1997 PI 3234923, PI 248901, Everglades 41, Ever-
7 rows per plot three replications
glades 71, Tainung 2
a
In all trials, the distances between the rows were 70 cm.
Table 4 Growth characteristics for all the tested parameters in all field trials
Basal Stem Diameter mm Factors
Maximum Leaf Area Index LAI Final Canopy height cm
Kopais,
1994
Varieties 271.20a
PI 3234923 12.00a
3.08 357.47b
Everglades 41 15.50b
4.54 15.25b
302.87b 4.37
Everglades 71 Tainung 2
16.00b 359.95b
3.83 15.50b
4.05 369.97b
JT1 Kopais,
1995
Varieties 13.77a
271.00a 2.02
PI 3234923 262.00a
PI 248901 14.32a
1.92 13.64b
256.00a 2.17
PI 318723 16.32a
3.44 Everglades 71
339.80b 14.32a
3.28 322.00b
JT1 Populations
15.15a 270.50a
2.65 320 000 plantsha
309.70a 170 000 plantsha
17.84b 1.76
Aliartos,
1997
Varieties PI 248901
277.70a 13.13a
3.07 12.96a
266.60a 3.12
PI 318723 14.90b
Everglades 41 3.99
314.90a 15.30b
314.40a 4.23
Everglades 71 15.23b
3.87 Tainung 2
293.80a
and their interaction on yields and yield compo- nents in the field trial of 1997 were also analyzed
as mentioned before. LSD multiple range tests were used in partitioning the means statistical
significance at the P = 0.05. The STATGRAPH- ICS statistical software was used in carrying out
the data analysis.
3. Results and discussion
