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Acta Agriculturae Scandinavica, Section B — Soil & Plant
Science
ISSN: 0906-4710 (Print) 1651-1913 (Online) Journal homepage: https://www.tandfonline.com/loi/sagb20
Apical bud removal increased seed yield in hemp
(Cannabis sativa L.)
Darja Kocjan Ačko, Marko Flajšman & Stanislav Trdan
To cite this article: Darja Kocjan Ačko, Marko Flajšman & Stanislav Trdan (2019) Apical bud
removal increased seed yield in hemp (Cannabis�sativa L.), Acta Agriculturae Scandinavica,
Section B — Soil & Plant Science, 69:4, 317-323, DOI: 10.1080/09064710.2019.1568540
To link to this article: https://doi.org/10.1080/09064710.2019.1568540
Published online: 13 Jan 2019.
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Apical bud removal increased seed yield in hemp (Cannabis sativa L.)
Darja Kocjan Ačko, Marko Flajšman and Stanislav Trdan
Biotechnical Faculty, Department of Agronomy, University of Ljubljana, Ljubljana, Slovenia
ABSTRACT
In plants, apical dominance prevents the development of lateral shoots. It can be overwhelmed by
apical bud defoliation, allowing numerous lateral buds to develop into more lateral branches
carrying more fruits and possibly increasing seed yield. This study tested this hypothesis on five
hemp (Cannabis sativa L.) cultivars in a 2-year field experiment. In comparison to the intact ones,
the defoliated plants developed several lateral shoots. The hemp seed yield was significantly
influenced by the year of production, the apical bud removal, and the cultivar. The average two-
year seed yield of the defoliated plants (715 ± 47 kg/ha) was significantly higher than the yield of
the intact plants (568 ± 35 kg/ha). Absolutely the greatest effect of apical bud removal on the
seed yield was observed for the cultivar ‘Novosadska konoplja’, where increase was 225 kg/ha
(25%); a slightly smaller difference occurred for the cultivar ‘Uniko-B’(183 kg; 30%), followed by
‘Juso-11’(140 kg/ha; 27%) and ‘Bialobrzeskie’(128 kg/ha; 29). Cultivar ‘Beniko’presented the
smallest difference with apical bud removal –58 kg/ha (15%) yield increase We maintain that
hemp producers can achieve a larger seed yield not only by selecting an appropriate cultivar
and row distance but also by removing apical buds.
ARTICLE HISTORY
Received 10 September 2018
Accepted 7 January 2019
KEYWORDS
Cannabis sativa; cultivars;
defoliation; height of plants;
seed yield
Introduction
Industrial hemp (Cannabis sativa L.) for harvesting in
the European Union, is a plant with a fibrous stem
and is a non-food raw material (European Commission
2000; Weightman and Kindred 2005). However, nutri-
tional qualities of hemp seed, rich in both oils and pro-
teins (Callaway 2004a), are recognised as alimentary
advantages (Andre et al. 2016) and lead to intensive
seed production (Salentijn et al. 2015). Demand for
cold-pressed oil, other foodstuffs and dietary sup-
plements made of hemp seeds has increased with
the recognition that consumption of hemp seed pro-
ducts may help prevent the emergence and develop-
ment of various diseases in humans (Rodriguez-Leyva
and Pierce 2010) and favourably influences the
growth and development of domestic animals,
especially poultry (Khan et al. 2010).
In hemp seed production, several constraints
decrease seed yield, and different cultivation tech-
niques are continuously tested (e.g. plant density, N
fertilising and sowing time). One of the approaches
to enhance yield in some agriculture crops is the
apical bud removal (defoliation). Apical dominance
seems not to be auxin related and is likely governed
by high sugar demand, which serves to slow the
growth of the axillary buds below (Mason et al.
2014). Once apical buds are removed, lateral shoots
massively develop. Studies on the reactions of plants
to apical bud removal include a variety of plant
types, including trees, ornamental shrubs, grapevines,
some garden crops and field crops (Lortie and
Aarssen 1997). In vegetable fruits, such as paprika,
tomatoes, aubergines, cucumbers, pumpkins and
melons, apical buds are regularly removed to increase
yield (Salisbury and Ross 1992). In hemp, however, con-
troversial information exists regarding hemp response
to defoliation (Small et al. 2007; Leonte et al. 2015;
Baldini et al. 2018), demonstrating that besides
edapho-climatic conditions, seed yield is also
influenced by the cultivar and applied agro-technique
measurements (e.g. plant density). This research
determined the seed yield and plant height in
response to apical bud removal for five hemp cultivars
in comparison with the yield from intact plants. It was
hypothesised that plants with apical buds removed
would produce a higher seed yield than the intact
plants.
© 2019 Informa UK Limited, trading as Taylor & Francis Group
CONTACT Stanislav Trdan stanislav.trdan@bf.uni-lj.si Biotechnical Faculty, Department of Agronomy, University of Ljubljana, Jamnikarjeva 101, Ljubljana
SI-1000, Slovenia
Supplemental data for this article can be accessed at https://doi.org/10.1080/09064710.2019.1568540
ACTA AGRICULTURAE SCANDINAVICA, SECTION B —SOIL & PLANT SCIENCE
2019, VOL. 69, NO. 4, 317–323
https://doi.org/10.1080/09064710.2019.1568540
Materials and methods
Plant material
For the analysis of apical bud removal, five cultivars were
chosen (Table 1), which were studied in 2000 and 2001,
when hemp production was being reintroduced in Slove-
nia (Kocjan Ačko et al. 2002). Since no hemp cultivars that
are intended specifically for seed production are mar-
keted, farmers sow the available cultivars, which are envi-
sioned for producing stems and fibres (Ranalli 2004; Vogl
et al. 2004). In comparison with the hemp grown for
fibres, wherein, producing long and thin stems requires
sowing with 12- do 15-cm row spacing (Schumann
et al. 1999; Young 2005), the production of hemp seed
normally involves 25- to 60-cm rows. This spacing
enables plants to develop lusher and branched inflores-
cences and thereby increase seed yield.
Field experiment
The field trials on the five hemp cultivars occurred in the
laboratory field of the Biotechnical Faculty in Ljubljana
(46°04′N, 14°31E, 299 m elevation), where the soil is
medium deep and silty-clay. Soil pH was 7.0 and the
level of K
2
O and P
2
O
5
was in the optimum range (20–
30 mg K
2
O 100 g of soil
−1
and 13–25 mg P
2
O
5
100 g of
soil
−1
). Plots were established on 20 April 2010 (from
now on referred to as year 1) and 24 April 2011 (from
now on referred to as year 2). The trial was arranged as
a randomised complete block design with three repli-
cates. The basic plot covered 5 m
2
(1 m × 5 m). Seeds
of each cultivar were sown manually at a row spacing
of 25 cm (4 rows) and a distance of 20 cm per row (25
plants per row) at a depth of 1.5 to 2.5 cm. A density of
approximately 100 harvested female or hermaphrodite
plants per basic plot was ensured, by placing two
seeds in the same spot. All seeds did not germinate; if
two plants grew close together, the weaker one was
cut. Since the sex of dioecious cultivars (‘Novosadska
konoplja’,‘Juso-11’) was unrecognisable before the
emergence of flowers, the desired number of 100
female plants (unisexual plants in the case of monoe-
cious cultivars) per basic plot was regulated until the
middle of the generative period.
In the years before the experimental sowing of hemp,
the field, which was fertilised with approximately 20 t of
animal manure per hectare, was used for growing pota-
toes; the pre-sowing treatment of the hemp field
involved using 40 kg of NPK per hectare (applied in a
15:15:15 formulation). The presence of weeds, due to
wider row spacing in the trials, was reduced first with
inter-row hoeing and, subsequently, with occasional
manual weeding. The growth and development of
hemp were monitored until the apical buds appeared
at the beginning of reproductive (flowering) phase.
Then, the removal of the apical buds (defoliation) was
carried out manually in the middle of June, in the
growth stage 2000, according to the decimal code devel-
oped by Mediavilla et al. (1998). Simultaneously, the
height at which the apical buds were removed was
measured. The control treatment was non-defoliated
plants. The final height of the plants was determined at
harvest on 5 and 6 September in year 1 and 2, respect-
ively. Inflorescences of the hundred plants from each
plot were cut manually and placed in paper bags
before oven drying at 40 to 50°C. The seeds were
removed from the inflorescences, by shaking and thresh-
ing while other materials were removed with sieves and
blown off. Seeds from the individual cultivars were
weighed, and the seed yield was calculated in kilograms
per hectare at 10% moisture.
In year 1, total monthly precipitation was lower than
the long-term average (1985–2010), except for August,
when rainfall was 176 mm (39 mm above the long-
term average). Temperatures were similar to the long-
term average, except in June and July, when it was
higher by 1.2 and 1.6°C, respectively. Year 2 had extre-
mely low precipitation in April (38 mm) and August
(43 mm), and high rainfall in July (157 mm). Tempera-
tures were mostly above the long-term average; at
most by 2.2°C, in August (Figure 1).
Statistical methods
Data on the seed yield (kg/ha) and final plant height
(cm) of the five hemp cultivars were analysed by the
general analysis of variance (ANOVA) to test the
effects of the year, cultivar, defoliation treatments and
their interactions and by individual ANOVA, to assess
the effects of cultivar and defoliation treatment within
each year. The averages were separated by Student–
Newman–Keuls multiple range tests at p< 0.05. Before
analysis, each variable was tested for homogeneity of
the treatment variances. If the variances were non-
homogeneous, data were transformed to log(y) before
ANOVA. All statistical analyses were performed with
Statgraphics Plus for Windows 4.0 (Statistical Graphics
Corp., Manugistics, Inc.). Data are presented as untrans-
formed means ± SE.
Table 1. List of origin, ecotype and sexual type of used cultivars.
Cultivar Origin Ecotype Sexual type
‘Beniko’Poland Northern, low-hemp Monoecious
‘Bialobrzeskie’Poland Northern, low-hemp Monoecious
‘Juso-11’Ukraine Middle European hemp Dioecious
‘Novosadska konoplja’Serbia Southern, high-hemp Dioecious
‘Uniko-B’Hungary Middle European hemp Monoecious
318 D. KOCJAN AČKO ET AL.
Results
Morphological appearance of the plants after the
defoliation
During the growth and development of the hemp,
special attention was paid to the transition from vegeta-
tive to generative development. The short cultivars ‘Bia-
lobrzeskie’and ‘Beniko’formed buds at the height of 70
to 80 cm while the other three, taller cultivars, formed
buds at the height of 90 to 100 cm. The defoliation
occurred first in the taller cultivars (‘Novosadska
konoplja’,‘Uniko-B’and ‘Juso-11’) and then a week
later in both short cultivars (‘Bialobrzeskie’and
‘Beniko’). After apical bud removal, the plants formed
lateral shoots, which eventually lengthened and
strengthened considerably. The majority of plants devel-
oped from two to three lateral shoots, with only a few
forming four to six such shoots. The lusher inflorescences
of the plants without apical buds acquired mass than the
intact plants, but no stems broke under the weight of the
seeds.
Influence of the year of production, defoliation
and cultivar on the seed yield and the final height
of the plants
Hemp seed yield was significantly influenced by the year
of production, defoliation and cultivar (p< 0.0001). The
average 2-year seed yields were greater for defoliated
plants than for non-defoliated plants (715 ± 47.0 vs 568
± 35 kg/ha), although the effect was more pronounced
in year 2 than year 1 (year × treatment interaction; p=
0.0125), for which, average hemp seed yields were 712
± 47 and 570 ± 35 kg/ha, respectively. Across years,
yields also differed by cultivar (year of production × the
cultivar interaction, p= 0.013). Cultivar yields decreased
in the order ‘Novosadska konoplja’(996 ± 50 kg/ha) >
‘Uniko-B’(697 ± 37 kg/ha) > ‘Juso-11’(595 ± 43 kg/ha) >
‘Bialobrzeskie’(502 ± 27 kg/ha) > ‘Beniko’(418 ± 12 kg/
ha) (Supplementary material, Table S1) and a significant
difference in yield was confirmed in all cultivars.
Plant height was also influenced by the year of pro-
duction, defoliation and cultivar (p< 0.0001). Plant
height was greater in year 2 (148 ± 4 cm) than year 1
(126 ± 4 cm), although year-to-year variation in this
response varied by cultivar (cultivar × year interaction;
p< 0.0001). Regarding plant height, the rank of the culti-
vars from significantly tallest to significantly shortest was
‘Novosadska konoplja’(165 ± 4 cm) > ‘Uniko-B’(140 ±
7cm) > ‘Juso-11’(132 ± 7 cm) > ‘Bialobrzeskie’(128 ±
5cm)>‘Beniko’(122 ± 4 cm). The cultivars also displayed
different responses to defoliation according to the year
(year of production × defoliation interaction, p=
0.0122), revealing that plants with removed buds were
significantly shorter (126 ± 4 cm) than the intact plants
(149 ± 3 cm) (Supplementary material, Table S2). Finally,
there was a 3-way interaction among the year of pro-
duction, defoliation and cultivar (p= 0.0065).
Comparison of seed yield and the final height of
defoliated and non-defoliated plants
In both years of the study, defoliation treatments
affected the seed yield of almost all cultivars significantly.
Figure 1. Mean monthly air temperature and total monthly precipitation during the field experiment and the long-term average
ACTA AGRICULTURAE SCANDINAVICA, SECTION B —SOIL & PLANT SCIENCE 319
In year 1, defoliation treatment (vs non-defoliation) sig-
nificantly increased seed yield only for ‘Novosadska
konoplja’(979 ± 46 vs 793 ± 6 kg/ha) and ‘Uniko-B’(717
± 50 kg/ha vs 557 ± 2 kg/ha). In year 2, the effect of defo-
liation was significant for all cultivars, except for Beniko
(474 ± 7 kg/ha vs 408 ± 8 kg/ha) (Figure 2). For average
seed yield of both years of the study, the strongest
effect of defoliation was observed for ‘Uniko-B’,in
which, apical bud removal enhanced seed yield by 30%
(183 kg/ha) as the average of the 2 years. There was a
slightly weaker effect of defoliation on ‘Bialobrzeskie’
(29%; 128 kg/ha), ‘Juso-11’(27%; 140 kg/ha) and ‘Novo-
sadska konoplja’, which had the highest absolute yield
differences (225 kg/ha), reflected by a 25% yield increase.
‘Beniko’seed yield only increased 15% (58 kg seed/ha)
(Supplementary material, Table S1). Plant high of all cul-
tivars significantly decreased by defoliation treatments in
both years of the study, except year 2, in which the
height of cultivar ‘Uniko-B’was not affected by defolia-
tion (Figure 3). The highest decreases in plant height
(on average of both years of the study) were observed
for cultivar ‘Bialobrzeskie’(23%; 26 cm) and ‘Juso-11’
(23%; 27 cm), followed by ‘Beniko’(21%; 23 cm) and
‘Uniko-B’(15%; 19 cm; p= 0.030). The height of the
highest cultivar ‘Novosadska konoplja’(165 ± 4 cm)
decreased by 13% (20 cm; p= 0.002).
Discussion
Hemp is cultivated for the biomass and seeds. With the
present production technology, hemp seed yield per
unit of area can vary considerably, with maximum
yields up to 2400 kg/ha in Europe (Tang et al. 2016;
Campiglia et al. 2017). Recent data show that farmers
in Slovenia produce 200 to 1600 kg of hemp seed per
hectare while yields of beginner farmers are usually
smaller than expected (Flajšman et al. 2017). The
average hemp seed yield in this study of 641 kg/ha,
means that yield could still be improved. However,
weather conditions were seen to affect seed yield. Year
2 favoured seed production, and average seed yield
was 142 kg/ha higher compared with year 1. The pro-
nounced weather effect also reflected in the plant
height, with a difference in average plant height of
15% (22 cm) in favour of year 2 (Supplementary material,
Tables S1 and S2). Although year 2 had less total precipi-
tation from April to September (443 mm) than year 1
(513 mm), the rainfalls were better distributed through-
out the growing season, especially, June and July
(active vegetative growth of plants) in year 2 had more
rainfall than in year 1. Besides, temperatures were
higher compared to the long-term records, except in
July (Figure 1). Conversely, in year 1, June was dryer
and July had a higher temperature in comparison to
the long-term data. Heavy precipitation in August prob-
ably impacted negatively on ripening of the seeds and
decreased the yield in this year.
The agrotechnical measure of defoliation in hemp is
frequently performed in practice, to derive cannabinoids,
terpenes and phenol substances from the resinous tri-
chomes of female blossoms (Andre et al. 2016). The
process technologically differs from the seed production
dealt with in the current study. Hemp seed production is,
operationally, usually occurs without apical bud removal.
In both cases, the removal of apical buds produces lateral
buds that form an inverse pyramidal crown with a great
Figure 2. The influence of the year of production and defoliation treatments (D –defoliation, ND –non-defoliation) on cultivar’s seed
yield. The mean yields of the cultivars were separated by a Student–Newman–Keuls multiple range test (p< 0.05) among defoliation
events within each year. The dotted line separates years. The values carrying the same letters do not differ significantly.
320 D. KOCJAN AČKO ET AL.
potential for producing secondary metabolites (Green
2003; Andre et al. 2016) and seeds.
The results of this study confirm the high influence of
the cultivar on seed yield (deviation from −35% to + 55%
from average yield), as stated previously by other authors
(Callaway 2004b; Vogl et al. 2004; Tang et al. 2016).
Besides, a statistically positive influence of apical bud
removal on the seed yield in all cultivars in both years
of the experiment occurred. This phenomenon has
been reported for cotton plants (Gossypium hirsutum L.)
as well (Sadras 1996; Bednarz and Roberts 2001). Further-
more, cultivar origin is related to seed yield. Southern
ecotype ‘Novosadska konoplja’yielded the highest
(996 ± 50 kg/ha), followed by both middle European eco-
types ‘Uniko-B’(697 ± 37 kg/ha) and ‘Juso-11’(595 ±
43 kg/ha), and then the northern European cultivars ‘Bia-
lobrzeskie’(502 ± 27 kg/ha) and ‘Beniko’(418 ± 12 kg/
ha). In addition, there was no connection between culti-
var origin and its response to defoliation since both
middle European ecotypes reacted with the highest per-
centage increase, and both northern European cultivars
reacted inconsistently. The response of the southern
ecotype ‘Novosadska konoplja’to defoliation was mod-
erate compared with the other cultivars. It is likely that
northern European cultivars, when grown in the area of
origin, would show enhanced yield and the defoliation
impact would be improved. However, in year 2, when
seed yields were higher relative to year 1, the effect of
defoliation was more pronounced in all cultivars.
This study showed that defoliation caused an average
25.9% increase in seed yield. Small et al. (2007) tested a
hypothesis that insect damage of the main stem of
hemp may be beneficial for seed yield. In that work, 62
hemp accessions were planted in a field previously culti-
vated with corn infested with European corn borer (ECB).
After the ECB invasion of hemp plants, the upper part of
the main stems was destroyed, causing very strong
branching. The results were a substantial increase in
biomass production (20%) and 9% decrease in plant
height. Seed yield was assessed but not quantified,
although, seed productivity was significantly positively
correlated (r= 0.33) with the percentage of ECB-
damaged plants. Small et al.’s(
2007)study verified the
positive effect of naturally occurring defoliation by ECB
invasion. However, the beneficial influence of insect
damage on hemp production is difficult to assess since
insect infestation cannot be controlled and its large out-
breaks could annihilate hemp crops.
Seeding density could have a crucial role in the
success of increasing seed yield by plant defoliation.
The current trial used a very low plant density of 20
plants per m
2
at harvest (row spacing of 0.25 m, and
inter-plant distance of 0.2 m). Instead, Baldini et al.
(2018) sowed 130 viable seeds per m
2
at 0.15 m inter-
row spacing and noticed a 34.5% (190 kg/ha) decrease
in seed yield after defoliation of eight monoecious
hemp cultivars, grown for multipurpose use. It is very
likely that the comparatively wider growing space in
the current experiment allowed defoliated plants to
occupy more space, develop more intensive branching
and, consequently, more seed yield. Planting density
could be highly associated with the success of defolia-
tion. This assumption was endorsed by Leonte et al.
(2015), who tested three defoliation treatments (non-
defoliation, cutting once and cutting twice) on three
monoecious hemp cultivars at two different row
Figure 3. The influence of the year of production and defoliation treatments (D –defoliation, ND –non-defoliation) on cultivar’sfinal
height. The mean heights of the cultivars were separated by a Student–Newman–Keuls multiple range test ( p< 0.05) among defolia-
tion events within each year. The dotted line separates years. The values carrying the same letters do not differ significantly.
ACTA AGRICULTURAE SCANDINAVICA, SECTION B —SOIL & PLANT SCIENCE 321
distances (25 and 50 cm) at very low sowing rate (6 kg/
ha). Although both the year of cultivation and cultivar
influenced seed yield, a wider row distance with an
increasing number of defoliations increased seed yield
by around 10%, on average.
In the current work, defoliated plants were 18.3%
shorter than the non-defoliated plants for the 2-year
average, which represents an advantage for mechanised
seed harvesting. Apical bud removal was considered to
have been timed appropriately (mid-June), which was
confirmed by the intensive growth of lateral buds into
inflorescences and, together, produced more seeds
than apical buds of intact plants. Based on the study
results presented, the removal of apical buds is rec-
ommended as an economically important agrotechnical
measure in the production of this widely useful field crop
(Bassetti et al. 1998; Struik et al. 2000; Amaducci et al.
2015; Kocjan Ačko 2015, Andre et al. 2016; Fike 2016).
Acknowledgement
This research was partly supported by grants from the Slove-
nian Research Agency, research programme P4-0077. The
authors are thankful to the reviewers for their collaboration
and valuable advices, which helped to improve this manuscript.
Disclosure statement
No potential conflict of interest was reported by the authors.
Notes on contributors
Dr. Darja Kocjan Ačko is an assistant professor-researcher in the
Dept. of Agronomy at the Biotechnical Faculty, University of
Ljubljana (Slovenia), where she works since 1985. Her experi-
ence areas are crop production, organic farming and nutritional
composition of plants. She has mentored over 70 Bsc and Msc
diploma thesis.
Dr. Marko Flajšman is a researcher in the Dept. of Agronomy at
the Biotechnical Faculty, University of Ljubljana (Slovenia) since
2012. His research topic is crop production, mainly hemp and
soybean.
Dr. Stanislav Trdan is a full professor-researcher in the Dept. Of
Agronomy at the Biotechnical Faculty, University of Ljubljana
(Slovenia), where he works since 1997. His research interests
are focused on environmentally acceptable plant protection,
especially in the field of agricultural entomology. He has pub-
lished more than 80 refereed articles.
References
Amaducci S, Scordia D, Liu FH, Zhang Q, Guo H, Testa G,
Cosentino SL. 2015. Key cultivation techniques for hemp in
Europe and China. Ind Crops Prod. 68:2–16.
Andre CM, Hausman JF, Guerriero G. 2016.Cannabis sativa:
the plant of the thousand and one molecules. Front Plant
Sci. 7:19. doi:10.3389/fpls.2016.00019.
Baldini M, Ferfuia C, Piani B, Sepulcri A, Dorigo G, Zuliani F,
Danuso F, Cattivello C. 2018. The performance and potential-
ity of monoecious hemp (Cannabis sativa L.) cultivars as a
multipurpose crop. Agronomy. 8(9):162.
Bassetti P, Mediavilla V, Spiess E, Ammann H, Strasser H,
Mosimann E. 1998. Hanfanbau in der Schweiz. Geschichte,
aktuelle situation, sorten, anbau und erntetechnik,
wirtschaftliche aspekte und perspektiven (In German).
Eidgenössische Tänikon, Switzerland: Forschungsanstalt
für Agrarwirtschaft and Landtechnik (FAT)-Berichte. Report
No.: 516.
Bednarz CW, Roberts PM. 2001. Spatial yield distribution in
cotton following early-season floral bud removal. Crop Sci.
41(6):1800–1808.
Callaway JC. 2004a. Hempseed as a nutritional resource: an
overview. Euphytica. 140(1–2):65–72.
Callaway JC. 2004b. Hemp seed production in Finland. J Ind
Hemp. 9(1):97–103.
Campiglia E, Radicetti E, Mancinelli R. 2017. Plant density and
nitrogen fertilization affect agronomic performance of indus-
trial hemp (Cannabis sativa L.) in Mediterranean environ-
ment. Ind Crops Prod. 100:246–254.
European Commission. 2000. Council Regulation (EC) No. 1673/
2000 of 27 July 2000 on the common organisation of the
markets in flax and hemp grown for fibre. Official J.
L193:16–22.
Fike J. 2016. Industrial hemp: renewed opportunities for an
ancient crop. Crit Rev Plant Sci. 35(5–6):406–424.
Flajšman M, VerbičJ, Šantavec I, Kocjan Ačko D. 2017. Yield of
foreign varieties of hemp (Cannabis sativa L.) in relation to
the end-uses (seeds and stems) and location. New chal-
lenges in Agronomy 2017 (In Solvenian with summary in
English). In: Čeh B, Dolničar P, MiheličR, Stajnko D,
Šantavec I, editor. Proceedings of the Symposium New
Challenges in Agronomy 2017; Jan 26–27; Ljubljana,
Slovenia: Slovensko Agronomsko društvo; p. 75–81.
Green G. 2003. The cannabis grow Bible: the definitive guide to
growing marijuana for recreational and medical use.
San Francisco (CA): Green Candy Press.
Khan RU, Durrani FR, Chand N, Anwar H. 2010.Influence of feed
supplementation with Cannabis sativa on quality of broilers
carcass. Pak Vet J. 30(1):34–38.
Kocjan Ačko D. 2015. Poljščine, pridelava in uporaba (In
Solvenian). Ljubljana, Slovenia: Kmečki glas. p. 101–118.
Kocjan Ačko D, BaričevičD, Rengeo D, Andrenšek S. 2002.
Economical important characteristics of five hemp varieties
(Cannabis sativa L. var. sativa)infields trials at Markišavci
near Murska Sobota. Proc Biotech Fac Univ Ljubl Agric
Agric Ser. 79(1):237–252.
Leonte A, Robu T, GăucăC, Pochişcanu S. 2015.Productionresults
obtained at monoecious hemp variaties for fiber after
“Secuieni method”. Lucrări Ştiinţific Ser Agron. 58(2):83–87.
Lortie CJ, Aarssen LW. 1997. Apical dominance as an adaptation
in Verbascum thapsus:effects of water and nutrients on
branching. Int J Plant Sci. 158(4):461–464.
Mason MG, Ross JJ, Babst BA, Wienclaw BN, Beveridge CA.
2014. Sugar demand, not auxin, is the initial regulator of
apical dominance. Proc Nat Acad Sci. USA. 111(16):6092–
6097.
322 D. KOCJAN AČKO ET AL.
Mediavilla V, Jonquera M, Schmid-Slembrouck I, Soldati A. 1998.
Decimal code for growth stages of hemp (Cannabis sativa L.).
J Int Hemp Assoc. 5(2):68–74.
Ranalli P. 2004. Current status and future scenarios of hemp
breeding. Euphytica. 140(1–2):121–131.
Rodriguez-Leyva D, Pierce GN. 2010. The cardiac and haemo-
static effects of dietary hempseed. Nutr Metab. 7:32.
Sadras VO. 1996. Population-level compensation after loss of
vegetative buds: interactions among damaged and unda-
maged cotton neighbours. Oecologia. 106(4):417–423.
Salentijn EMJ, Zhang Q, Amaducci S, Yang M, Trindade LM.
2015. New developments in fiber hemp (Cannabis sativa L.)
breeding. Ind Crops Prod. 68:32–41.
Salisbury FB, Ross CW. 1992. Plant Physiology. Belmont (CA):
Wadsworth Publishing Company. p. 357–407.
Schumann E, Peil A, Weber WE. 1999. Preliminary results of a
German field trial with different hemp (Cannabis sativa L.)
accessions. Genet Resour Crop Evol. 46(4):399–407.
Small E, Marcus D, Butler G, McElroy AR. 2007. Apparent
increase in biomass and seed productivity in hemp
(Cannabis sativa) resulting from branch proliferation
caused by the European corn borer (Ostrinia nubilalis). J Ind
Hemp. 12(1):15–26.
Struik PC, Amaducci S, Bullard MJ, Stutterheim NC, Venturi G,
Cromack HTH. 2000. Agronomy of fibre hemp (Cannabis
sativa L.) in Europe. Ind Crops Prod. 11(2–3):107–118.
Tang K, Struik PC, Yin X, Thouminot C, Bjelková M, Stramkale V,
Amaducci S. 2016. Comparing hemp (Cannabis sativa L.) cul-
tivars for dual-purpose production under contrasting
environments. Ind Crops Prod. 87:33–44.
Vogl CR, Mölleken H, Lissek-Wolf G, Surböck A, Kobert J. 2004.
Hemp (Cannabis sativa L.) as a resource for green cosmetics:
yield of seed and fatty acid compositions of 20 varieties
under the growing conditions of organic farming in
Austria. J Ind Hemp. 9(1):51–68.
Weightman R, Kindred D. 2005.Review and analysis of
breeding and regulation of hemp and flax varieties
available for growing in the UK. Project NF0530. Final
report for the Department for Environment, Food and
Rural Affairs. London, UK: ADAS Centre for Sustainable
Crop Management.
Young EM. 2005. Revival of industrial hemp: a systematic
analysis of the current global industry to determine limit-
ations and identify future potentials within the concept of
sustainability [master’s thesis]. Lund, Sweden: Lund
University.
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