228 S.D. Koutroubas et al. European Journal of Agronomy 11 1999 227–237
type of climate, castor plants could be adapted tions, cultural practices and time of harvesting.
Hooks et al. 1971 found that the seed oil content satisfactorily taking into account their environ-
mental requirements. However, since castor plants is negatively correlated with days to flowering and
with the number of nodes to the first and second have not been systematically cultivated in Greece,
information about the performance and the yield racemes and positively correlated with the number
of racemes per plant and volume weight of seed. of the crop are lacking. Such data are necessary
in order to explore the feasibility of the castor oil High temperatures, above 35
°C, and water stress during the flowering and oil formation can reduce
as an alternative crop in Greek agriculture. Seed yield depends on the number of racemes
the seed oil content Weiss, 1983. Early harvesting of immature or still green capsules can also
per plant, the number of capsules per raceme and the thousand seed weight. Under natural condi-
adversely affect the seed oil yield. The purpose of this work was to study the
tions, the castor plant has many racemes, depend- ing on the number of branches, that develop
adaptability of new castor plant genotypes in the environmental conditions of Northern Greece and
progressively over the life of the plant. This is an undesirable characteristic for commercial pro-
to evaluate their yielding ability during the 3 years of experimentation.
duction since the high number of racemes results in an extended maturity period, thus making
mechanical harvesting
uneconomical. Low
branched plants with one to three racemes resistant to shattering are desirable in modern castor
2. Materials and methods
varieties. The number of capsules per raceme depends on
The experiments were carried out at the farm of the Aristotle University of Thessaloniki, Greece,
the number of female flowers on the raceme. Castor plants are normally monoecius, with male
and at the farm of the Cereal Institute in the village of Loudias, 50 km west of Thessaloniki in
flowers on the upper portion of the raceme and female on the lower. Flowers of both types can
the years 1995, 1996 and 1997. The soil on the University farm was a sandy clay loam with a pH
also be interspersed along the length of the raceme. The proportion of male and female flowers on
of 7.85, 0.85 organic matter, and a water-holding
capacity of 0.34 cm 3 cm−3, and at Loudias, the
each raceme varies and can be influenced by the environment Weiss, 1983. The inflorescence can
soil was a clay loam with a pH of 7.65, 3.48 organic matter, and a water-holding capacity of
reach a length of 100 cm, but since there is a wide variation in the distance between flowers, yield is
0.44 cm 3 cm−3. At Loudias, the underground
water level was higher than on the University not necessarily correlated with length.
The plant height varies between 3 and 10 m in farm. Castor plants followed wheat on the
University farm and corn at Loudias in 1995 and perennial types but is much lower in annual plants
Bonjean, 1991. For mechanical harvesting, the 1997 and wheat in both locations in 1996.
Nineteen castor plant genotypes were tested in plant height should be low. The node at which the
first raceme appears is also an important agro- both locations Table 1. The genotypes were
hybrids, except Venda and Polluce, which were nomic characteristic, since it is associated with
early maturity. It is a varietal characteristic and, inbred lines. In order to study as many genotypes
as possible and to examine their yield variation in dwarf-internode cultivars, usually occurs after
the sixth to twelfth node, but in a segregating over years, the genotypes that combined high seed
and oil yield and morphological characteristics population can vary from six to 45 Zimmerman,
1957. However, dwarf cultivars are at present less appropriate for mechanical harvesting were tested
for 2 or 3 years, whereas the less promising geno- productive
than normal-internode
cultivars Laureti, 1981.
types were tested for 1 year only. A randomized complete block design with four replications was
The seed oil content depends on the genotype but is also affected by the environmental condi-
used. Plots were 10 m long and consisted of six
229 S.D. Koutroubas et al. European Journal of Agronomy 11 1999 227–237
Table 1
Trifluralin applied at a rate of 1200 g ha−1 pre-
Time from sowing to the beginning of female flowering on the
sowing, and linuron applied
at a rate of
first raceme of 19 castor plant genotypes a
680 g ha−1 pre-emergence, together with hoeing using a hoe or rotovator at the three- to six-leaf
Genotype Time days
stage, were used for weed control in both locations.
1995 1996
1997
At Loudias, fluazifop butyl was used for Sorghum halepense control in 1996. The insecticide furadan
UF L
UF L
UF L
10 G was applied uniformly in the soil surface at
Negus 65
63 57
44 65
53
a rate of 35 kg ha−1 before sowing and incorpo-
Pronto 60
56 52
43 57
51
rated together with the fertilizers. At Loudias,
H530 62
48 68
55
deltamethrin at a rate of 18.75 g ha−1 was used in
H526 55
44 58
49
1995 and 1996 for Agrotis control.
HD912 54
44 64
53 Riscio
69 61
62 46
Irrigation was applied in both locations. A drip
B9 71
68 73
61
irrigation system was used, after emergence, on
H523 61
57
the University farm, and the total amount of water
Venda 68
60
used each year 280 mm in 1995 and 300 mm in
Polluce 60
56
1996 and 1997 corresponded to about 70–75 of
114 68
65 929
62 57
the evapotranspiration in the area, measured by
H101 61
47
the pan evaporation method Doorenbos and
125 61
42
Kassam, 1986 in Laureti and Marras, 1995. At
519 57
45
Loudias, the irrigation water about 140 mm in
Castore 58
49
1995, 250 mm in 1996 and 200 mm in 1997 was
H531 65
56 H529
65 56
applied by sprinkler, and the time of irrigation
H913 67
58
was determined when temporary midday plant wilting had occurred.
a UF: University farm; L: Loudias.
In 1996, the plants were sprayed with 20 diquat at a rate of 1000 g ha−1 at Loudias in order
to destroy any green leaves and to facilitate the rows, 0.6 m apart on the University farm and five
rows, 0.8 m apart, at Loudias. harvest.
Data regarding dates of emergence, female The experimental area on the University farm
was uniformly fertilized with 80 kg N ha−1 as flowering, first brown full capsule, first brown
raceme, maturity for harvest and temperature sums ammonium sulphate, 48 kg P ha−1 as superphos-
phate, and 91 kg K ha−1 as potassium sulphate base temperature 10
°C, Arnaud, 1990 for each stage of development were collected each year.
each year and at Loudias with the same amounts in 1995, 100 kg N ha−1 and 24 kg P ha−1 in 1996
Two seed harvests were carried out in 1995: the first when up to the three racemes were brown and
and 80 kg N ha−1 and 18 kg P ha−1 in 1997 before planting.
the second when the rest of the racemes had matured. One seed harvest was carried out in 1996
Seeds were hand-planted on 10, 26 and 18 April on the University farm and 11, 25 and 23 April at
and 1997, when almost all the capsules on the mature racemes became brown. At harvest, six
Loudias in 1995, 1996 and 1997, respectively. The row distance was 0.33 m on the University farm
plants from the two central rows of each plot were cut at ground level, and the insertion height of the
and 0.25 m at Loudias, in order to achieve yields of approximately 50 000 plants ha−1 in both loca-
first raceme, the plant height and the number of secondary brown racemes with full capsules were
tions. Three seeds were planted in each hill, and the plots were hand thinned to one plant per hill
measured. Then, the first raceme and the other racemes were separately collected from the four
when the plants were at the four- to six-leaf stage. In all years, seed germination and plant emergence
central rows of each plot for yield and yield component determinations. The yield percentage
were helped by light sprinkler irrigation.
230 S.D. Koutroubas et al. European Journal of Agronomy 11 1999 227–237
of the first raceme and the others and the thousand and r
=0.899, p0.01 at Loudias but not in the other years. The maturity of the first raceme was
seed weight were calculated on a dry-seed basis. The oil content was measured by the Soxhlet
completed from the beginning to the middle of August in all genotypes in all three years 49–
method American Oil Chemists’ Society, 1983 in 1995 and 1996 and by nuclear magnetic resonance
62 days after the beginning of the flowering on the University farm and 48–64 days at Loudias, fol-
NMR spectrometry in 1997. NMR estimates of oil
content were
calibrated against
Soxhlet lowed by a period of about 1.5 months with
favourable environmental conditions for the matu- estimates.
A statistical analysis was performed according rity of secondary racemes. On the University farm,
122–137 days were needed for the maturity of the to Steel and Torrie 1980. The homogeneity of
the variances was checked, and all measured and reproductive racemes and at Loudias more time,
121–151 days, because the mean over genotypes derived data were subjected to analysis of variance
combined over locations separately for each year. number of secondary racemes was higher. The
corresponding temperature sums base temper- A combined analysis of variance over locations
and years was also performed for the data concern- ature 10
°C varied from 1421 to 1792 d°C on the University farm and 1377 to 1895 d
°C at Loudias, ing the genotypes used for more than one year.
LSD values were calculated and used to compare depending mainly on the genotype rather than on
the years of experimentation. treatment means. The relative contribution of the
seed yield and the seed oil concentration to the sum of squares of the oil yield was determined by
linearizing the multiplicative relationships by 3.2. Morphological characteristics
taking logs according to the method of Moll et al. 1982. According to this analysis, the sum of
The plant height and the height of insertion of the first raceme differed between locations and
cross products of each component trait by the resultant trait
∑x i
y i
divided by the sums of among genotypes in all years. The locations
× genotypes interaction was significant in 1995 and
squares of the resultant trait ∑y
2 i
gives the relative contribution of each component variable to the
1996 for the plant height and only in 1997 for the height of insertion of the first raceme Table 2.
resultant variable. The over genotypes mean values of both character-
istics were higher at Loudias compared to those on the University farm, but the differences between
3. Results
