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Trakya Univ J Sci, 4(2): 187-194, 2003
ISSN 1302 647X
DIC: 90LATT410312030104
INVESTIGATIONS ON YIELD AND QUALITY OF KOHLRABI
(Brassica oleraceae var. gongylodes L.) IN THE TRAKYA REGION of
TURKEY
Levent ARIN, Ahmet SALK, Murat DEVECI, Serdar POLAT
Department of Horticulture, University of Trakya, 59030 Tekirdağ, Turkey, e-mail: arinlevent@hotmail.com
Received : 09.04.2003
Accepted : 28.07.2003
Abstract: This research was carried out to determine the possibility of growing kohlrabi (Brassica oleraceae var.
gongylodes L.) under Trakya (Turkey) conditions during the spring and fall growing periods in the year of 2000. In
each period, three kohlrabi cultivars (Express Forcer, Neckar, Lahn), two seedling ages (four or six weeks old) and
three planting dates (at two week intervals in April, May for spring and in September, October for fall), with respect
to yield and quality characteristics, were evaluated. Cultivars Neckar and Express Forcer had higher yield and quality
than Lahn in both seasons. Higher yield was obtained from six weeks old seedlings in the spring, while a period of
four weeks was sufficient for growing seedlings in fall.
Key words : cultivars, kohlrabi, planting date, seedling age, yield
Trakya Bölgesi'nde Alabaş (Brassica oleraceae var. gongylodes L.) Verim ve Kalitesi Üzerine Araştırmalar
Özet: Bu araştırma 2000 yılı ilkbahar ve sonbahar döneminde Trakya koşullarında alabaş (Brassica oleraceae var.
gongylodes L.) yetiştirme olanağını belirlemek amacıyla yürütülmüştür. Her bir periyotta üç alabaş çeşidi (Express
Forcer, Neckar, Lahn), iki fide yaşı (dört ve altı haftalık) ve üç dikim zamanı (iki hafta aralıklarla ve ilkbaharda Nisan
ve Mayısta, sonbaharda Eylül ve Ekimde) verim ve kalite özellikleri bakımından değerlendirilmiştir. Neckar ve Exp-
ress Forcer çeşitleri her iki sezonda da Lahn'dan daha yüksek verim ve kalite vermiştir. Sonbaharda dört haftalık süre
fide yetiştirme süresi yeterliyken, ilkbaharda altı haftalık fidelerden daha yüksek verim elde edilmiştir.
Anahtar kelimeler : alabaş, çeşit, dikim zamanı, fide yaşı, verim
Introduction
Turkey has 79 million hectares area with a wide
variety at soil and climate. A large range of crops spe-
cies including many horticultural crops are grown in
approximately 36% of this land area. In Turkey, pro-
duction of horticultural crops is around 29 million tons
and approximately 70% of this production is vegetable
crops. The country is among the top five vegetable
producing countries in the world in term of production
and area. Vegetable crops are commonly grown in
Mediterranean (south), Aegean (west) and Marmara
(northern-west) regions. Tomatoes, water melons, on-
ions melons and cucumbers are the most commonly
grown vegetable crops in Turkey. Cabbage, belonging
to Cruciferae family, ranks among the top eight with a
total production of approximately 577 000 tons. Vege-
table crops also have a significant place in the agricul-
tural exports of the country. For instance, Turkey ex-
ported 370 000 tons of fresh vegetables in 1999,
which corresponds to 19 million US$. Export of fresh
as well as processed vegetables, is a rapidly growing
agro-industry sector in Turkey. Russian Federation,
Germany, Saudi Arabia are the biggest importing
countries of Turkish vegetables, although Turkish
vegetal products (including vegetables) are exported
to 50 countries, (Anonymous a, 2000; Anonymous b,
2000; Vural et al., 2000).
Trakya which is located in north-west of the coun-
try has a wide range of climates and soil conditions
and therefore almost all vegetables can be grown. But,
the greater part of agricultural land is being used to
produce the field crops such as wheat and sunflower.
The gross income value of vegetables is over 4.5%,
while vegetables utilize 1.03% of the total agricultural
area of the province.
The demand for vegetables is on the rise due to in-
creasing population, changing food habits, realization
of high the nutritional value of vegetable crops and
Original Article/Orijinal Makale
Levent ARIN, Ahmet SALK, Murat DEVECI, Serdar POLAT
188
greater emphasis on value addition and export in Tur-
key as well as the entire world. Presently, growers are
directed towards new crops instead of traditional crops
such as wheat and sunflower due to changes in the last
agricultural policy and structural adjustments in Turkey.
Kohlrabi (Brassica oleraceae var. gongylodes L.),
belongs to the large and agriculturally important fam-
ily Cruciferae is a fast growing cool season vegetable
crop. It is grown primarily for its enlarged stem that is
rich in nutritional components, especially with respect
to vitamin C and potassium. The enlarged stem of the
plant can be eaten raw, cooked or preserved, while its
young leaves can be used for salads or cooked like
spinach. It is widely grown in northern, central Europe
and America (Splittstoesser, 1990; Krug, 1991; Lieb-
ster, 1991). According to vegetable production re-
cords, there is no kohlrabi production in Turkey, while
other members of Cruciferae family such as cabbage,
cauliflower, and radish are grown in almost all parts of
the country (Vural et al., 2000). Kohlrabi can be an al-
ternative crop for vegetable growers due to it's similar-
ity to other Cruciferae members, having a short grow-
ing season and its export possibility. Unfortunately, a
supply and demand study on kohlrabi in Turkey is not
available for producers and researchers. The objective
of this study was to investigate this possibility and
prepare a background for future kohlrabi researches.
Materials and Methods
This study was planned to determine the possibil-
ity of growing kohlrabi (Brassica oleraceae var.
gongylodes L.) in the Trakya region and was carried
out at the experimental field at the Trakya University,
Faculty of Agriculture (lat 40º59'N, long 27º29'E, alt 4
m asl), and Department of Horticulture in 2000. This
area is classified as semi arid, with a cool, rainy sea-
son from November to April, and a hot, dry season
from May to October. According to long term climatic
data, the mean annual rainfall is about 580 mm, and
means air temperatures vary from 4.5 (in January) to
23.3 ºC (in July). The experiment was carried out for
two seasons (spring and fall). Three cultivars [Express
Forcer (Takii-Japan), Neckar and Lahn (Rick Zwaan-
Netherlands)], three planting dates (at two weeks in-
terval in April, May for spring and in September, Oc-
tober in fall) and two-seedling ages (four or six weeks
old) were used to determine suitable cultivars, plant-
ing dates and seedling age for each season. The culti-
vars are F1 hybrid and white skinned varieties. Lahn
and Neckar are recommended for summer and fall
crops in north-west Europe. Express Forcer is early
maturing and the most commonly cultivated in various
region of the world. They are suitable for open field
production (Rijk Zwaan, 2000; Takii, 2000).
Seeds of all cultivars were sown at depth of 1 cm
by hand into plug-trays filled with commercial peat-
like mixes. The properties of growing medium are
given in Table 1. The individual cells of plug-trays
contained approximately 100-ml of mix.
Table 1. The properties of growing media.
N (mg/l) P2O5 (mg/l) K2O (mg/l) pH EC (µs/cm)
100-300 100-300 150-400 5.4-5.9 350
Planting dates were determined by taking account
of meteorological data and requirement of kohlrabi.
The monthly air temperature, precipitation, relative
humidity and soil temperature of the experimental area
during the growing periods were presented in Table 2.
Average temp.
(ºC)
Average
max. temp. (º C)
Average
min. temp. (ºC)
Precipitation
(mm)
Relative
humidity (%)
Soil temp. (depth
at 5 cm,ºC)
April 14.0 19.7 11.0 48.5 84.8 17.1
May 16.6 21.8 12.0 67.0 77.2 20.8
June 20.9 24.8 15.9 11.8 72.2 25.9
July 25.4 28.3 19.3 0.0 68.7 30.5
August 24.4 28.8 19.6 18.1 71.7 28.3
September 20.3 24.8 13.8 20.6 77.1 24.1
October 14.9 18.7 10.9 82.2 81.3 17.0
November 12.7 16.1 9.9 9.2 85.9 14.0
December 8.7 15.8 5.7 10.1 80.2 8.9
Table 2. The monthly air temperature, precipitation, relative humidity and soil temperature of the experimental area dur-
in
g
the
g
rowin
g
p
eriods.
Investigations on yield and quality of kohlrabi
(Brassica oleraceae var. gongylodes l.) in the Trakya Region of Turkey
Trakya Univ J Sci 4(2), 187-194, 2003
189
Four or six weeks old seedlings of each cultivar
were transplanted into a ground bed in the field in
each planting date. Plants were spaced 0.30 m within
the rows and 0.40 m between rows. Plots were culti-
vated and irrigated as needed. The field soil was a silty
clay loam with a pH 7.4, with organic matter levels at
1.7%. Soil test results indicated that additional K2O
was not required for kohlrabi production, but 120 kg
N ha-1and 60 kg P2O5 ha-1 were applied to the soil.
Compose (20-20-0) and ammonium nitrates (26-0-0)
were used as fertilizer. Half of the N and the entire
P2O5 utilized were incorporated prior to planting as a
basal dressing and the remaining N was applied three
weeks after planting. Benomyl was applied periodi-
cally as a fungicide while endosulfan and diazinon
used as insecticides in the study.
The following parameters were measured or evalu-
ated: number of leaf (bigger than 2 cm), leaf weight
(g), tuber weight (g), tuber diameter (mm), tuber index
(diameter/height ratio), tuber ratio [tuber weight/plant
weight (%)], and yield [total plant weight per plot
(kg)] were recorded for each treatment. Soluble solid
content was determined by hand held refractometer.
The leaf area was measured using scanner.
The experiment was established as a factorial ran-
domized block design with three replications. Data
were subjected to analysis of variance, with factorial
comparisons of main effects and interactions. Means
were tested by protected LSD (at the 0.05 level).
MSTAT 3.51 was used for analysis of variance.
Results
The harvest dates ranged from 52 to 63 days after
planting depending on cultivars and growing season.
Only the main effects of cultivar and planting dates in
the spring were significant for leaf properties (number,
weight or area) (Table 3). Neckar had the lowest leaf
number (11.4), but gave the highest value in term of
leaf weight and area. The second planting date ranked
first for average leaf number of 13.5, leaf weight of
86.0 g and leaf area of 12.5 dm2 . Differences among
cultivars were important for the soluble solid content.
The SSC of cv. Lahn, was 5.6 % higher than other cul-
tivars. The soluble solid content of tubers was lower
for the first planting date (3 April) compared to the
last planting date, and was 5.1 and 5.5, respectively.
The main effects of cultivar and seedling age and
their interaction had a significant effect on tuber
weight, and the highest value was obtained from 6
week old seedlings of E. Forcer (815.0 g) and lowest
from Lahn for both seedling ages (Table 4 and 5). The
results regarding tuber diameter was similar to results
for tuber weight. Among cultivars, Neckar and E.
Forcer had larger tubers than Lahn (respectively 114.7
and 107.2 mm). Although there were no big differ-
ences between values obtained from planting
date×seedling age interaction, the greatest value
(109.7 mm) was obtained from 6 weeks-old seedlings
of second planting time of Neckar and lowest value
(99.7 mm) from 4 weeks-old seedlings of same plant-
ing time of Neckar. Tuber index was significantly af-
fected by cultivar, planting date, seedling age and
planting date×seedling age interaction. While the low-
est tuber index (0.97) was found in Lahn, index of
Leaf
number
Leaf
weight
Leaf
area
Soluble solid
content
Cultivars
E. Forcer
Neckar
Lahn
Planting dates
04-03-00
04-17-00
05-01-00
12.2 a
11.4 b
13.0 a
12.5 a
13.5 a
10.6 b
79.9 a
85.7 a
53.7 b
61.4 b
86.0 a
71.9 ab
10.7 ab
13.1 a
9.4 b
9.2 b
12.5 a
11.4 ab
5.2 b
5.1 b
5.6 a
5.1 b
5.4 a
5.5 a
Cultivars Planting dates
LSD 0.05 (Leaf number ) : 1.21 LSD 0.05(Leaf number) : 1.20
LSD 0.05 (Leaf weight) :17.81 LSD 0.05(Leaf weight) : 17.81
LSD 0.05 (Leaf area) : 2.64 LSD 0.05(Leaf area) : 2.64
LSD 0.05 (Soluble solid cont) : 0.31 LSD 0.05(Soluble solid cont) : 0.31
Table 3. Main effects of cultivar and planting date on leaf number, leaf weight (g), leaf area (dm2), soluble solid content of tu-
b
er
(
SSC
,
%
)
for s
p
rin
g
g
rowin
g
season.
Levent ARIN, Ahmet SALK, Murat DEVECI, Serdar POLAT
190
Neckar and E. Forcer were greater than one. In plant-
ing date×seedling age interaction, all applications
were placed at the same importance group, except for
6 weeks-old seedling which was planted on 3 April.
As can be seen from Table 4, differences only among
cultivars in point of yield were statistically important.
Neckar gave the highest yield (15.616 kg). E. Forcer
which was placed at the same group with Neckar
ranked in the second position with an average yield of
14.606 kg. The lowest yield was obtained from Lahn
(9.787 kg). There were no significant differences for
tuber ratio (data not shown).
For the fall growing period, leaf number was af-
fected by cultivar, planting date, and seedling age and
cultivar × planting date interaction (Table 6, 8).
Among cultivars, E. Forcer, among planting dates,
first planting time, and between seedling ages, 6
weeks-old seedling had the highest number of leaf. In
term of leaf weight, differences among cultivars,
planting date, seedling age were significant. Culti-
var×planting date interaction was also significant.
Lahn planted on 4 September gave the lowest value
with 56.6 g, while the heaviest leaves were obtained
from Neckar which was planted on 18 September (av-
erage 98.0 g). Leaf weight of plants planted as 4
weeks-old seedlings was greater than other seedling
ages. The results of leaf area were similar with those
of leaf weight. Leaf area varied for cultivars ranged
from 12.5 to 15.6 dm2 depending on cultivars and the
highest value was obtained from Neckar. Among
planting times, those planted on the 18th of September
gave the highest leaf area (16.1 dm2).
Table 4. Main effects of cultivar, planting date and seedling age on tuber weight (g), tuber diameter (mm), tuber index (tuber
diameter/tuber hei
g
ht
)
and
y
ield
(
k
g
/
p
lot
)
for s
p
rin
g
g
rowin
g
season.
Tuber
weight
Tuber
diameter
Tuber
index
Yield
Cultivars
E. Forcer
Neckar
Lahn
Planting dates
04-03-00
04-17-00
05-01-00
Seedling age
6 weeks
4 weeks
722.4 a
762.0 a
495.6 b
698.7
630.6
650.6
692.9 a
627.1 b
107.2 a
114.7 a
94.8 b
105.6
104.7
106.5
105.9
105.3
1.19 a
1.11 ab
0.97 b
0.96 b
1.18 a
1.12 ab
1.01 b
1.18 a
14.606 a
15.616 a
9.787 b
13.087
13.082
13.840
13.845
12.828
Cultivars Planting dates
LSD 0.01 (Tuber weight) :105.21
LSD 0.01 (Tuber diameter) : 7.57
LSD 0.01 (Tuber index) : 0.17 0.17
LSD 0.01 (Yield) : 2.30
Table 5. Effect of cultivar×seedling age interaction on tuber weight (g), and planting date×seedling age interaction on tuber di-
ameter
(
mm
)
and tuber index
(
tuber diameter/tuber hei
g
ht
)
for s
p
rin
g
g
rowin
g
season.
Cultivar and
seedling age
Tuber
weight
Planting date and
seedling age
Tuber
diameter
Tuber
index
E. Forcer 6 week
4 week
815.0 a
629.8 b
04-03-00 6 week
4 week
101.9 ab
109.2 a
0.77 b
1.17 a
Neckar 6 week
4 week
768.9 a
755.0 a
04-17-00 6 week
4 week
109.7 a
99.7 b
1.18 a
1.19 a
Lahn 6 week
4 week
494.8 c
496.4 c
05-01-00 6 week
4 week
106.1 ab
106.8 ab
1.08 a
1.18 a
cultivar×seedling age planting date×seedling age
LSD 0.05 (Tuber weight) : 110.82 LSD 0.05 (Tuber diameter) : 7.98
LSD 0.05 (Tuber index) : 0.18
Investigations on yield and quality of kohlrabi
(Brassica oleraceae var. gongylodes l.) in the Trakya Region of Turkey
Trakya Univ J Sci 4(2), 187-194, 2003
191
Significant differences were observed between cul-
tivars, planting date and seedling age for soluble solids
content. Lahn, second planting time and 4 week old
seedling had highest value 9.0, 8.2 and 7.8% respec-
tively (Table 6). A significant difference among
cultivars was observed in tuber weight (Table 7). Av-
erage tuber weight of E. Forcer was 280.8 g, while
Lahn had the lightest tubers (105.0 g). Tuber diameter
was significantly affected by cultivar, planting date
main effect and cultivar×seedling age interaction.
Among planting dates, the third planting date gave the
highest tuber diameter. Among cultivar×seedling age
interaction (Table 9), tuber diameter was less for Lahn
than other cultivar combinations. Based on the results
of tuber index, all main effect and interactions were
statistically important, except for planting
date×seedling age (Table 7, 9). While the tuber index
of E. Forcer planted on 4th of September was less than
one, all of others had greater diameter than tuber
height. Tuber index changed between 1.09 and 1.41
depending on cultivar×seedling age combination, and
the highest values were obtained from Lahn in both
seedling age and Neckar planted at 4 weeks old seed-
ling period. Tuber ratio was significantly affected by
main effects and cultivar×seedling age interaction.
Among planting dates, the second planting time gave
Table 6. Main effects of cultivar, planting date and seedling age on leaves number, leaves weight (g), leaf area (dm2), soluble
solid content of tuber
(
SSC
,
%
)
for fall
g
rowin
g
season.
Leaf
number
Leaf
weight
Leaf
area
Soluble solid
content
Cultivars
E. Forcer
Neckar
Lahn
Planting dates
09-04-00
09-18-00
10-02-00
Seedling age
6 week
4 week
16.8 a
14.0 b
13.0 c
17.0 a
14.5 b
13.2 c
15.4 a
13.4 b
70.3 b
84.9 a
74.2 ab
63.7 b
87.4 a
78.3 a
68.6 b
84.2 a
12.5 b
15.6 a
13.8 ab
11.4 b
16.1 a
14.3 ab
12.6 b
15.2 a
6.4 c
7.3 b
9.0 a
7.4 b
8.2 a
7.3 b
7.3 b
7.8 a
Cultivars Planting dates
LSD 0.01 (Leaf number ) : 0.91 LSD 0.01 (Leaf number) : 0.91
LSD 0.01 (Leaf weight) :10.98 LSD 0.01 (Leaf weight) :10.98
LSD 0.01 (Leaf area) : 2.19 LSD 0.01 (Leaf area) : 2.94
LSD 0.01 (Soluble solid cont) : 0.69 LSD 0.01 (Soluble solid cont) : 0.69
Table 7. Main effects of cultivar, planting date and seedling age on tuber weight (g), tuber diameter (mm), tuber index (tube
r
diameter/tuber hei
g
ht
),
tuber ratio
(
tuber wei
g
ht/
p
lant wei
g
ht
,
%
)
and
y
ield
(
k
g
/
p
lot
)
for fall
g
rowin
g
season.
Tuber
weight
Tuber
diameter
Tuber
index
Tuber
ratio
Yield
Cultivars
E. Forcer
Neckar
Lahn
Planting dates
09-04-00
09-18-00
10-02-00
Seedling age
6 weeks
4 weeks
280.8 a
275.4 a
105.0 b
227.6
200.5
243.2
225.5
225.4
80.6 a
78.8 a
60.4 b
69.8 b
71.6 b
78.4 a
72.3
74.3
1.10 c
1.28 b
1.39 a
1.14 b
1.31 a
1.32 a
1.21 b
1.31 a
78 a
73 b
58 c
73 a
64 b
72 a
71 a
68 b
6.631 a
6.208 b
3.374 b
5.156
5.390
5.666
5.294
5.515
Cultivars Planting dates
LSD 0.01 (Tuber weight) :53.95
LSD 0.01 (Tuber diameter) : 7.63 5.396048
LSD 0.01 (Tuber index) : 0.05 0.0463738
LSD 0.01 (Tuber ratio) : 4.98 4.981345
LSD 0.01 (Yield) : 1.13
Levent ARIN, Ahmet SALK, Murat DEVECI, Serdar POLAT
192
the lowest tuber ratio with 64%, the other two planting
times were not significantly different from one an-
other. When yield is considered, it was observed that
the differences between cultivar and cultivar×seedling
age interaction were statistically important (Table 7,
9). The yield of E. Forcer and Neckar was higher than
Lahn. The yield of Lahn was approximately one half
of the other cultivars.
Discussion
Yield of kohlrabi is generally evaluated as the re-
sult of tuber size. During the spring growing season,
tuber weight, diameter, and yield values were the
greater than during the fall growing season. There is a
high probability that this correlates with the higher
temperature and light conditions of spring. Fink and
Krug (1989) found that the growth rate of tuber
diameter and leaf area at 18 ºC were greater than those
of 10 ºC, and Wendt (1978) reported that increasing
the soil temperature from 5 to 20 ºC produced larger
stems in cv. Roggli's Weisser Treib, particularly with
increasing light. Yamaguchi (1983) determined that
the recommended temperature range for production of
kohlrabi is 18-25 ºC, with the optimum at 22 ºC. Also,
it has been suggested by Krug (1991) that a tempera-
ture of at least 12 ºC is needed during the growing pe-
riod of kohlrabi.
In the spring growing period, tuber weight, tuber
diameter and yield ranged between 495.6 and 762.0 g,
94.8 and 107.2 mm and 9.787 and 15.616 kg respec-
tively, depending on cultivars (Table 4). These results
are in agreement with those of Glukhov (1973), who
obtained 23 t ha-1 yield in kohlrabi, and Krug (1991),
that suggested tuber diameter must be more than 40
mm for fresh market, but average tuber weight values
are higher than those of Mehwald (1976), in which he
reported that average tuber weight varied in 430 to
475 g in nine kohlrabi cultivars. Among cultivars, the
highest tuber values were obtained from Neckar and
E. Forcer. The authors hypothesize that Lahn did not
do well due to sensitivity to different ecological condi-
tions, although cv. Lahn is recommended as summer
crop in the north-west Europe (Rickzwaan, 2000).
Also, Vanparys (1999), working with twelve kohlrabi
cultivars to determine the best cultivar for industrial
processing, found that Lahn gave the lowest tuber
weight among cultivars. In this study, although leaf
number of Neckar was less than other cultivars, this
Table 8. Effect of cultivar×planting date interaction on leaves number, leaves weight (g) and tuber index (tuber diame-
ter/tuber hei
g
ht
)
for fall
g
rowin
g
season.
Cultivar and
planting date
Leaf
number
Leaf
weight
Tuber
index
09-04-00
E. Forcer 09-18-00
10-02-00
19.6 a
16.5 b
14.3 cd
59.1 d
85.5 ab
66.0 cd
0.82 b
1.28 a
1.20 a
09-04-00
Neckar 09-18-00
10-02-00
15.4 bc
13.9 cde
12.6 e
75.2 bc
98.0 a
80.5 b
1.23 a
1.28 a
1.33 a
09-04-00
Lahn 09-18-00
10-02-00
13.4 d
13.1 de
12.6 e
56.6 d
77.8 bc
88.3 ab
1.37 a
1.37 a
1.43 a
LSD 0.01 (Leaves number) : 1.58 LSD 0.01 (Leaves weight) :14.17 LSD 0.01 (Tuber index) :0.25
Table 9. Effect of cultivar×seedling age interaction on tuber diameter (mm), tuber index (tuber diameter/tuber weight), tube
r
ratio
(
tuber wei
g
ht/
p
lant wei
g
ht
,
%
)
and
y
ield
(
k
g
/
p
lot
)
for fall
g
rowin
g
season.
Cultivar and
seedling age
Tuber
diameter
Tuber
index
Tuber
ratio
Yield
E. Forcer 6 week
4 week
78.8 a
82.9 a
1.09 b
1.21 b
79 a
78 a
6.317 a
6.945 a
Neckar 6 week
4 week
81.8 a
75.8 a
1.17 b
1.40a
79 a
67 b
6.928 a
5.488 ab
Lahn 6 week
4 week
56.7 b
64.1 b
1.37 a
1.41 a
57 c
59 c
2.637 c
4.110 bc
LSD 0.01 (Tuber diameter) :7.63 LSD 0.05 (Tuber index) : 0.15
LSD 0.05 (Tuber ratio) :7.04 LSD 0.05 (Yield) : 1.60
Investigations on yield and quality of kohlrabi
(Brassica oleraceae var. gongylodes l.) in the Trakya Region of Turkey
Trakya Univ J Sci 4(2), 187-194, 2003
193
cultivar had the highest leaf weight and area. The
highest tuber weight, diameter and yield were ob-
tained from Neckar. This can be attributed to increases
in photosynthetic efficiency as depend on large as-
similation surface and suitable shape, size, position
and number of cell layers of photosynthetic tissue. In
terms of tuber weight, generally, 6 week old seedlings
of cultivars, except for Lahn, were heavier than 4
week old seedlings (Table 5). It is commonly regarded
that seedling development level is related to growing
conditions, especially in relation to temperature and it
is recommended that the lowest day temperatures
should be 12-15 ºC during seedling growing period in
kohlrabi (Fink and Krug, 1989; Wiebe et al., 1992).
Unsuitable weather conditions before first planting
time may reduce the seedling growth level. Regarding
tuber index, only the index value of 6 weeks old seed-
ling of Lahn planted on 3 April were less than one
(Table 4, 5). This situation relates cultivar and seed-
ling growing conditions. Fritz and Stolz (1989) sug-
gested that weather conditions (especially cool
weather) influence tuber formation in some varieties.
During the fall growing period, the highest tuber
weight, diameter and yield were produced by E.
Forcer (Table 7). Within the studies carried out in dif-
ferent places utilizing different cultivars, Vanparys
(1996) reported that E. Forcer was the highest among
twenty one kohlrabi varieties in term of yield, Van-
parys (1988) suggested that E. Forcer was one of the
best suited cultivars for the fresh market, Lippert
(1995) demonstrated that E. Forcer was more resistant
to cracking than other varieties, and Habegger and
Wiebe (1986) indicated that cultivar E. Forcer re-
mained in marketable quality at maturity after a 9-
week vernalization treatment at 6 ºC. During this pe-
riod, Lahn was ranked lowest in the characteristics
mentioned above. Both 4 week old seedlings of E.
Forcer and Lahn gave higher tuber diameter and yield,
compared to Neckar (Table 9). This result indicates
that the 4 week seedling growing period was sufficient
for the fall season. These findings are consistent with
the reports of Janssen (1983), who determined that the
development period of kohlrabi seedlings was short in
summer and longer in winter, Muehmer et al., (1987),
stated that older transplants resulted in elongated
plants, and delayed maturity, rough fruit, decreased
yield and poorer grades. Despite the lower leaf weight
and area of E. Forcer, it had the highest leaf number,
tuber ratio, and the highest yield and yield compo-
nents. These results indicate that E. Forcer has a
higher number of narrow, light leaves with a large part
of the plant consisting of tuber. Although the only sig-
nificant difference observed was between planting
dates, generally, tuber weight, diameter, yield of
plants planted on 2 October were greater than those of
the first two fall planting dates due to more suitable
environmental conditions for kohlrabi.
Leaf area varied from 9.2 to 13.1 dm2 (Table 3) in
spring season and from 11.4 to 16.1 dm2 (Table 6) in
the fall. These results correspond with those of Sritha-
ran and Lenz (1992) where measured leaf area was be-
tween 8.4 and 12.4 dm2 in different light regimes. In
both growing seasons, Lahn had the highest value with
regards to SSC. This can be attributed to the cultivar
properties of Lahn.
In conclusion, cultivars Neckar or E. Forcer can be
suggested for both growing seasons, utilizing six week
old seedlings in the spring, and four week old seedling
in the fall. Planting dates did not have a clear effect in
spring and the last planting date in fall little positive
effect on tuber properties and yield. Further research is
needed regarding cultivar selection and should be car-
ried out for the improvement of the results presented
above.
Acknowledgement: This project was supported for
the period 1999-2001 by Research Fund of Trakya
University (Project No. 269). We are grateful to Re-
search Fund for financial support.
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