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
3
.
1
. Growth characteristics Growth rate was rather high for all varieties
until the flowering phase up to 4.38 cmday and thereafter it was gradually decreased. It is re-
ported Petrini et al., 1994 that kenaf has an indeterminate type of growth with rapid growth
rate increases until the appearance of the first flowers and gradual decreases afterwards.
In all
trials, early-maturity
varieties PI
3234923, PI 248901 and PI 318723 were shorter than the late ones Everglades 41, Everglades 71,
Tainung 2 and JT1. The early-maturity varieties grew 267 cm tall, averaged over the years and
sites. Correspondingly, the late-maturity varieties reached a mean height of 330 cm. In the first and
the second trial this superiority was statistically significant Table 4. More specifically, final
canopy height of the early varieties varied from 256 cm PI 318723, 1995 to 277.7 cm PI 248901,
1997 and the late ones from 298.80 cm Tainung 2, 1997 to 369.97 cm JT1, 1994. Plant popula-
tion did not significantly influence the canopy height, though a certain superiority of the low
plant density was highlighted Table 4.
Basal stem diameter was larger for the late varieties 15.36 mm compared with 13.30 mm.
This superiority was statistically significant in the case of first and the third trial Table 4. Basal
stem diameter recorded in the low-density plots was significantly higher 17.84 mm compared
with the high-density plots 15.15 mm. Leaf area index LAI of all the tested varieties
reached maximum values on different dates, de- pending on their maturity type. Early varieties
reached the highest values for LAI around 215 Julian date, while the late ones gave the peak
values 35 – 40 days later. In Table 4, only the maximum values are presented, irrespective of the
sampling date, therefore statistically significant differences could not be traced. However, it can
be seen that the mean max LAI of the early varieties, averaged over the years and sites, was
considerably low, 2.56 compared to 3.95 that was recorded for the late-maturity varieties. Regarding
the max LAI for each plant density, presented in Table 4, it refers to 251 Julian day and it is
averaged over all the tested varieties of the trial. According to the table, denser plantations re-
sulted in higher maximum LAI values.
3
.
2
. Yields Fresh and dry matter accumulation, as pre-
sented in Fig. 3, varied considerably according to the maturity type of kenaf varieties, while site
effect was rather negligible. More specifically, fresh and dry matter accumulation for all the
tested varieties early and late was similar until 240 Julian day, when the early varieties bloomed.
Thereafter, yield accumulation of the early vari- eties was gradually declined until the end of the
growing period. In contrast with the early vari- eties, fresh and dry matter yield accumulation for
the late ones exhibited a rapid increase until the 300 Julian day, when the peak values were
recorded, that is 60 days later that the early varieties. Thereafter, yields were sharply declined
due to the defoliation of the plants and the de- crease of the biomass moisture content Fig. 3.
It should be pointed out that fresh and dry matter yield components in all trials were found
to vary considerably from August to the end of the growing period, according to the maturity
type of the tested varieties. In all trials the varia- tion was statistically significant LSD test, P =
0.05 Table 5. It can be seen that, in general, late varieties
were more productive than the early ones. Maxi- mum yields of 44.39 and 73.7 tha fresh matter
were recorded for the early and late-maturity varieties, respectively, averaged over the years and
sites. Correspondingly, mean dry matter yields were 10.14 and 18.99 tha. As previously men-
tioned, the maximum yields of the early varieties refer to 240 Julian day, while the maximum yields
of the late varieties refer to the 300 Julian day. Late kenaf varieties achieved higher yields due to
the fact that they remained vegetative two months more than the early ones. As reported Petrini et
al., 1994 there is a positive relation between kenaf productivity and absence of the flowering
phase.
Each year, the peak values for fresh and dry matter yields were recorded from late October
until early November Fig. 3. At that time the harvest was carried out in a larger area 8.4 m
2
compared to the other harvests 0.7 m
2
, in order to assure more realistic estimations. Means for
fresh and dry matter yields and yield components, at this harvest are presented in Table 5. Early
varieties produced fresh biomass yields that ranged from 24.64 tha PI 3234923, 1994 to
33.34 tha PI 238901, 1997, while the dry matter yields ranged from 6.27 tha PI 3234923, 1995 to
9.40 tha PI 318723, 1997. Correspondingly, late varieties resulted in fresh yields that varied from
52.78 tha Everglades 71, 1995 to 88.66 tha Tainung 2, 1994 and dry matter yields from
13.32 tha Everglades 71, 1995 to 23.95 tha Tainung 2, 1994.
The high plant population 320 000 plantsha gave higher values for fresh and dry matter yields,
compared to the low one 170 000 plantsha. In Table 5, it can be seen that, though plant popula-
tion was doubled, the relative increase in yields was only 4.5 for fresh and 1.1 for dry matter.
It is worth mentioning that statistically significant differences between the two populations were
recorded only in the period from the beginning of growth until the beginning of the flowering phase
of the early varieties 240 Julian day. Thereafter and until the end of the growing period, the
superiority of the high plant density over the low one, as far as the fresh and dry matter yields are
Fig. 3. Fresh and dry matter yields accumulation for all tested varieties and all trials 1994, 1995 and 1997.
Table 5 Means of the yields and yield components LSD test, P = 0.05 for all the tested parameters in all field trials
Factors FBY
a
tha DMY
b
tha FSY
c
tha DSY
d
tha FLY
e
tha DLY
f
tha Kopais, 1994 Julian day, 315
Varieties 7.07a
24.60a 7.09a
24.64a
g
0.00a PI 3234923
0.00a 19.75b
66.40b 18.10b
Everglades 41 8.00ab
74.42b 1.59b
20.43b 72.10b
17.30b 87.36b
15.20c Everglades 71
0.07c 23.95b
Tainung 2 78.50b
88.66b 21.70b
10.10bc 2.19bc
21.90b 70.00b
20.10b 78.57b
8.50abc JT1
1.93bc Kopais, 1995 Julian day, 299
Varieties 6.27a
23.57a 5.82a
2.05a 0.45a
PI 3234923 25.62a
6.60a 24.46a
6.03a 26.60a
2.14a PI 248901
0.57a 6.24a
23.39a 5.64a
PI 318723 2.24a
25.77a 0.60a
13.32b 40.71b
11.44b 52.78b
12.07b Everglades 71
1.88b JT1
16.39b 60.93b
47.50b 13.48b
17.00b 2.90b
Populations 9.82a
320 000 plantsha 32.71a
38.90a 8.49a
7.67a 0.96a
37.20a 170 000 plantsha
9.71a 31.14a
8.48a 6.53a
1.60a Aliartos, 1997 Julian day, 298
Varieties 9.18a
24.76a 7.31a
33.34a 8.57a
PI 248901 2.08a
9.40a 25.24a
6.71a PI 318723
8.09a 33.32a
2.47a 16.53b
49.52b 12.42b
72.38bc 22.85c
Everglades 41 4.11b
79.52c Everglades 71
20.73c 55.24b
15.84c 24.28c
4.89c 17.92bc
50.00b 14.16bc
18.57b 3.76b
68.57b Tainung 2
a
FBY, fresh biomass yields.
b
DMY, dry matter yields.
c
FSY, fresh stem yields.
d
DSY, dry stem yields.
e
FLY, fresh leaf yields.
f
DLY, dry leaf yields.
g
Meand followed by the same letter do not differ significantly PB0.05, LSD test.
concerned, was still recorded, though it was not statistically significant.
Among the trials, in 1995 fresh and dry matter yields and yield components were lower compared
to the other two trials, as far as Everglades 41 and JT1 are concerned. These lower yields could be
related to the lower nitrogen fertilization rate 34 that was applied that year.
At the end of the season, in the first field Kopais, 1994, bark and core were separated and
fresh and dry matter yields for each fraction along with the bark to core ratio were assessed. The
relative data are presented in Tables 6 and 7.
4. Conclusions
