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Variation in mineral composition in three different plant organs
of five fibre hemp (Cannabis sativa L.) cultivars
L.G. ANGELINI1,*, S. TAVARINI1, B. CESTONE1, C. BENI2
1 Department of Agriculture, Food and Environment, University of Pisa, Pisa, Italy
2 Agricultural Research Council, Soil-Plant System Research Center (CRA-RPS), Rome, Italy
Received 11 November 2013 – Received in revised form 31 January 2014 – Accepted 3 February 2014
Keywords: bark, core, fibre hemp, mineral composition, nutrient uptake.
Abbreviations: BD, bulk density; CEC, cation exchange capacity; EC, elec-
trical conductivity; ICP-OES, inductively coupled plasma optical emission
spectrometry; SOC, soil organic carbon; SOM, soil organic matter; THC,
∆
9-tetrahydrocannabinol
S. – Five fibre cultivars of Cannabis sativa L. were grown in a field experiment
during two consecutive seasons in Central Italy with the aim to establish the pattern of
the macro- and micronutrient accumulation in three different plant organs (leaves, bark
and core) and to evaluate the nutrient uptake and partitioning within the plant in order
to gaining knowledge on their nutrient requirements. The cultivar and the kind of organ
significantly influenced both the macro- and micronutrient concentration of fibre hemp
with the highest concentrations in leaves followed by bark and core. The only exceptions
were S, Fe, Ni and Al, which had different distribution within the plant organs. The two
parts of the stem showed significant variations in macro- and micronutrient composi-
tions. The nutrient uptake and partitioning within the plant were primarily dependent
on cultivar characteristics in term of total dry yield. The Italian dioecious cultivars
(Carmagnola, C.S., Fibranova, Red Petiole) resulted more productive than the French
monoecious Felina 34, however this behaviour does not reflect on total uptake, since the
yield components, definitively influenced the total nutrient removal.
I. – Fibre hemp (Cannabis sativa L.) is a C3 herba-
ceous crop easy to grow worldwide, due to its agronomic potential in
a great range of environmental conditions (I et al., 1997; W
W and T, 2008) and its morphological and biological
characteristics (A et al., 2008a,b). Despite the excellent quality
of its bast fibres, in Europe hemp cultivation has declined significantly
after World War II, due to the presence of psychoactive compounds,
such as ∆9-tetrahydrocannabinol (THC) (R and V, 2004;
Z et al., 2012). Although all hemp genotypes contain THC, indus-
Agrochimica, Vol. 58 - No. 1 January-March 2014
* Corresponding author: luciana.angelini@unipi.it
L.G. ANGELINI ET AL.
2
trial fibre hemp genotypes contain a THC concentration 50 times lower
than that detected in illegal hemp (C et al., 2001; B
et al., 2010), as recommended by the Regulation EC n. 1124/2008 (12nd
November 2008).
In order to promote environmental-friendly and sustainable agricul-
tural systems, in the last years fibre hemp has been reintroduced in both
conventional and organic cropping systems because it may reduce cereal
monocropping, preserving soil fertility, and it is suitable for innovative
industrial applications (i.e. biocomposites in automotive and construc-
tions industries, raw materials for thermal insulation, oil and agro-fine
chemicals, etc.) (W W et al., 1994; R and V,
2004; B et al., 2010; Z et al., 2012).
The factors that influence both quality and quantity of hemp prod-
ucts are numerous, among which climate, soil conditions, genetic mate-
rial and agro-technique (B and K, 1998; A et al.,
2008c; A et al., 2012; C et al., 2012) are considered
as the most important. Fibre hemp can grow well and reach high biomass
yields per hectare with low inputs under a wide range of agro-ecological
conditions (S et al., 2000; A et al., 2012; Z et al.,
2012). At the same time, attention is required for several hemp physi-
ological features and their interaction with the environmental conditions.
In fact, dioecious and monoecious varieties grown under different cli-
matic regions may have different susceptibility to temperature and day
length (A et al., 2012; C et al., 2012). Consequently,
large potential exists to increase hemp crop yield by exploring the geno-
type × environment interaction (A et al., 2012; C et
al., 2013). The choice of the appropriate site-specific genotype become
important for hemp cultivation in the Mediterranean areas, characterised
by spring-summer high temperatures and water stress. In these climatic
conditions hemp has already demonstrated to be able to reach high dry
matter yield (from 14.0 to 22.5 Mg ha-1) (S et al., 2000; R
and V, 2004; C et al., 2013), even if it is not always
clear the optimal nutrient input needed to reach such high yield levels.
Furthermore few studies have been carried out on the mineral composi-
tion and nutrient requirements by fibre hemp cultivars of different ori-
gin, in particular when cultivated under the Mediterranean conditions.
Only a few studies were focused on the mineral composition of
fibre hemp and most of them were reported from Central or North-East
of Europe (I et al., 1997; H et al., 2009). Reliable data on
ACCUMULATION OF NUTRIENTS IN FIBRE HEMP CVS
3
the nutrient concentrations in fibre hemp could be an important diag-
nostic tool for the optimisation of mineral fertilisation, as well as for the
quantification of possible nutrient deficiencies and the residual nutrient
concentrations to the soil.
Hemp has large and deep root systems and high potential for remov-
ing nutrients and water from the soil (I et al., 1997; A et
al., 2008a). Therefore, investigations on nutrient requirements by hemp
crop became very relevant, since it can affect not only the plant biomass
production, but also the relationship between plant and soil. Although
hemp requires high amounts of nutrients, most of them can return to the
soil in a significant extent through the leaves. In fact, it should be con-
sidered that during the vegetative growth a part of the total fresh biomass
returns to the soil, because part of the senescent leaves falls down to the
ground or it is directly left on it after harvesting (B et al., 2003).
In addition, a part of removed nutrients could be returned into the soil
from the stem portions (i.e. core) after on-field decortication, and also
by the taproots, which remain directly in the soil (B et al., 2003;
A et al., 2008a). B et al. (2003) reported that 20-25% of
the removed nutrients, in particular macronutrients, can be returned to
the soil from the leaves and stems left in the field after harvest.
The main objectives of the present research were: (i) to establish the
pattern of the nutrient accumulation (macro- and micronutrients) in three
different plant organs (leaves, bark and core) of four dioecious and one
monoecious fibre hemp cultivars grown in Central Italy in a two-year
field trial; (ii) to evaluate the nutrient uptake and partitioning within the
plant in order to establish removal amounts.
M M. – Chemicals. – All chemicals as analytical quality
reagents and commercial stock element solutions used were provided by Sigma-Aldrich
Co. (St. Louis, MO, USA). All solutions were made with high purity water (Millipore,
Molsheim, France).
Growing conditions and experimental set-up. – The field trials were performed
in Central Italy at the Experimental Centre of the Department of Agronomy and
Agroecosystem Management of Pisa University (localized 15 km SW of Pisa-Italy,
43°40’N, 10°19’ E, 10 m above sea level) during the 2005 and 2006 growing seasons.
The region is characterized by a flat morphology and Mediterranean climate, with
minimum low temperature in January (2°C as mean monthly value), maximum high
temperature in July (29°C as mean monthly value), and rainfall mainly concentrated
in the autumn and spring (941 mm year-1). The experimental soil was an alluvial deep
loam, typical of the lower Arno River plain, classified as Typic Xerofluvent by the Soil
Taxonomy USDA system (USDA, 1999). It is characterised by a good water holding
capacity (field capacity: 27.3% dw, wilting point: 9.45% dw) and by a shallow water
L.G. ANGELINI ET AL.
4
table (120 cm deep under driest conditions). The pre-crops were castor bean in 2005 and
rapeseed in 2006. Soil tillage was done in November 2004 and 2005 with 30 cm deep
ploughing and by two superficial disk harrowings at the end of March 2005 and 2006,
to prepare the sowing bed. Plants were maintained under identical fertilization condi-
tions throughout the two-year field experiment. Before planting, mineral fertilizers were
applied at rates of 120/80/120 kg ha-1 of N/P/K (urea, triple superphosphate and potas-
sium sulphate, respectively). The N fertilization was split in two applications of 50%
(pre-planting) and 50% (before inter-row closure). No additional irrigation was needed
after sowing, either during the summer, due to the natural soil water availability.
Five European fibre hemp cultivars were compared in a small plot field experiment
with a randomized block design with four replicates (plot size was 20 m2, 5 m x 4 m,
in both years): Carmagnola, C.S., Fibranova and Red Petiole as Italian dioecious, and
Felina 34, French monoecious. Seeds were kindly supplied by CRA-CIN (Bologna,
Italy) and did not exceed the legal 0.2% THC (on dry matter basis, w/v). Hemp culti-
vars were sown on 27th April 2005 and 4th April 2006 by a pneumatic drill with 0.18 m
inter-row in order to achieve the planned crop density of 130-140 plants m-2. In order
to protect crops against weeds, hand and mechanical weeding were applied without any
herbicide treatment. During the growing period, emergence and flowering dates were
recorded when at least 2/3 of plants showed the specific phenological stage. The harvest
was carried out at flowering, corresponding to the phenological codes 2103 and 2302 for
dioecious and monoecious varieties, respectively (M et al., 1998). Depending
on weather conditions, harvesting dates were different in the two years. In 2005 the
harvest was from the beginning of July to the end of August, while in 2006 it was from
the end of June to the beginning of August.
Soil sampling and analyses. – Soil sampling was conducted on site in March 2005
and 2006 before hemp sowing. Duplicate soil cores (30 cm depth) were randomly taken
from each plot with a 5 cm diameter manual auger. These samples were then dried at
30°C and sieved (2 mm) prior to analysis. Soil characterisation was carried out according
to Soil Survey Laboratory Methods Manual (USDA-NRCS, 1996). The main physical-
chemical characteristics of the soil sampled in the two subsequent years (2005 and 2006)
are summarised in Table 1. Soil pH was potentiometrically measured in a soil-water
suspension (1:2.5, w/v) (M, 1982). Soil organic carbon (SOC) was determined as
reported by the modified Walkley-Black wet combustion method (N and S,
1996). Cation exchange capacity (CEC) was determined by the barium chloride-trieth-
anolamine (pH = 8.1) method, according to M (1938). Soluble salts were detected
by measuring the soil solution’s ability to conduct an electrical current, referred to as
electrical conductivity (EC) (R, 1969). The soil C/N ratio was computed as the
quotient of organic C and N concentrations. Bulk density (BD) was determined by a
separate undisturbed soil core (7 cm diameter) collected from a depth of 0-30 cm from
each plot and for each tested year. It was calculated dividing the mass of the oven-dried
sample at 105°C for 48 h by the volume of the probe (USDA-NRCS, 1996).
The exchangeable macronutrients, such as Mg, Ca and K, and beneficial mineral
elements (Na, Co and Al), were determined using the T method (1982). Total N
content was evaluated prior each experiment by the macro-Kjeldahl digestion procedure
(B and M, 1982), while available P was determined by colorimetric
analysis using the Olsen method (O and S, 1982). All analyses were carried
out in three replicates in order to control intra-laboratory variability.
ACCUMULATION OF NUTRIENTS IN FIBRE HEMP CVS
5
To determine the plant available microelements, diethylenetriaminepentaacetic acid
(DTPA)-extractable Co, Fe, Mn, Cu, Zn, Ni, Mo and B were analysed using 30 g of
dried soil by adding 60 mL of 5 mM DTPA, 10 mM CaCl2 and 0.1 M triethanolamine
(pH 7.3) solution (L and N, 1978). After 2 h shaking (60 cycles min-
1), soil samples were centrifuged at 17,400 g. Total soil S and Al concentration was
determined after wet digestion according to I et al. (1994). For determination of
available/total elements, analysis of the filtrates was performed using the inductively
coupled plasma optical emission spectrometry (ICP-OES) equipped with a ICAP 6100
(Thermo Scientific, Waltham, MA, USA) spectrometer. The analytical parameters of
ICP-OES were an applied power of 1.3 kW, a nebulizer follow rate of 0.8 L min-1, a
plasma gas flow of 15 L min-1 and an auxiliary gas flow of 2.0 L min-1. Prior to each
sample evaluation, the ICP-OES instrument was calibrated with a blank and four multi
element standard solutions.
Plant sampling and analyses. – The plants on a 10 m2 sampling area in the inner part
of each plot were hand cut at 4-5 cm from soil and weighed to determine fresh weight.
The border plants in the two outer rows were not included in the harvested area. The
aerial part of the plant was separated in the different plant organs (stem and leaves) and
allowed to dry into a forced-draft oven at 65°C till constant weight for dry weight deter-
mination. On 20 representative fresh plants per plot, the stems were cut into three equal
parts and the bark was manually separated from the core on the middle part of the stem,
according to L et al. (2013) and then allowed to dry in the same conditions described
before. Dried samples were ground in a Retsch SM1 rotor mill to < 297 µm prior the
subsequent analysis. Macro- and micronutrients, as well as beneficial mineral elements
were classified according to M (1995) and E and B (2005).
Macronutrients (N, S, P, Mg, Ca and K), micronutrients (Fe, Mn, Cu, Zn, Ni, Mo and B),
and beneficial elements (Na, Co and Al) were determined in all different parts (leaves,
bark and core) of each studied cultivar. Dried plant material was then digested for 24 h
with 10 mL of concentrated HNO3, using the same ICP-OES instrument described above
and at the same conditions, except N, which was determined using Kjeldahl digestion
(J, 1998). For ICP measurements, two types of standard reference materials were
used: BCR-679 (white cabbage, IRMM, Geel, Belgium) and ERM-CD281 (rye grass,
IRMM, Geel, Belgium). The certified reference materials were analysed in the same
experimental conditions used for the sample analyses in order to evaluate the accuracy
and precision of the method.
Statistical analysis. – Experimental results were evaluated by one-way analysis of
variance (ANOVA) using COSTAT version 6.400 (1998-2008 Cohort software). The
cultivar or the plant organ were considered as variability factors. Differences among
means were assessed by the Fisher’s Least Significant Difference (LSD) test at the 0.05,
0.01 and 0.001 probability levels, respectively.
R D. – Soil characteristics and nutrient con-
tent. – In the two-year field experiment, the soil did not significantly
change its chemical parameters (pH, SOC, CEC, EC, C/N ratio and
BD), as well as the macronutrients (total N and S, available P, exchange-
able Mg, Ca and K) and exchangeable Na, available Co and total Al
content. Therefore, the mean physical and chemical characteristics of
L.G. ANGELINI ET AL.
6
soil, used for 2005 and 2006 field trials, are presented in Table 1. The
most representative macronutrient was N followed by S > Ca > Mg > K
> P, whereas among the beneficial mineral elements, Al was the most
abundant followed by Na > Co. The soil showed a medium level in
organic carbon (9.8 and 9.9 g kg-1 SOC, respectively, corresponding to
1.7% soil organic matter as mean value), total N (1.23 and 1.28 g kg-1
in 2005 and 2006, respectively) and exchangeable K (80.0 and 85.6 mg
kg-1, respectively). The relatively high K content may be explained by
the high content of illites in clay, as characteristic of Typic Xerofluvent
soils in the Mediterranean basin (B et al., 1996). At the same
time, a low-medium available P content (14.6 and 17.4 mg kg-1, in 2005
and 2006 respectively) occurred. Generally, the availability of nutrients
in the soil is directly affected by pH (MP et al., 2000), which
in both seasons resulted sub-alkaline (7.82 and 7.81, in 2005 and 2006
respectively). The above-mentioned soil characteristics were favourable
for hemp growth. This crop, in fact, requires well-drained, well-struc-
tured, silty loam soil, rich in organic matter and nutrients (B and
K, 1998; S et al., 2000).
It is well known that minerals in soils are able to supply all the
microelements needed for plant growth in low amounts (E and
B, 2005). Soil macronutrients and micronutrient concentrations
were similar in the two-year experimental soil, and the most frequently
occurring pattern was Fe > Mn > Cu > Ni > Zn > B > Mo (Table 1).
The most abundant soil micronutrient was Fe (225.5 and 239.4 mg kg-1,
in 2005 and 2006, respectively), which was higher (+6%) in 2006 than
in 2005 soil. In contrast, Zn and B contents were lower in 2006 than in
2005 (-37 and -33%, respectively). These light variations in micronutri-
ent contents between the two years could be probably due to the crop
residual amount and quality left to the soil by the crops grown before
hemp. Considering the nutrient soil supply and the applied fertilizers,
the five cultivars grew without shortage of macro and micronutrients.
Mineral composition of hemp. – In Tables 2, 3 and 4, the concentra-
tions of the mineral elements were reported, separately for each plant
organ, cultivar and year of cultivation. In both growing seasons, N was
the dominant plant macronutrient, followed by K and Ca. On the other
hand, P, Mg and S were present at lower concentrations compared to the
previous macronutrients (Table 2). Considering the mean concentration
over the cultivars, all macronutrients accumulated mainly in the leaves,
in both years of cultivation. On the other hand, the different parts of the
ACCUMULATION OF NUTRIENTS IN FIBRE HEMP CVS
7
stem (bark and core) showed variations in macronutrient allocations: the
concentration of N, P, and K in the bark was significantly higher than in
the core, while an opposite trend was observed for S, but only in 2006.
T 1. – Mean soil physical-chemical characteristics in the experimental site
sampled at 0-30 cm depth in March of two years (2005 and 2006) before planting.
Parameters Mean
Sand (g kg-1) 443.6
Silt (g kg-1) 410.5
Clay (g kg-1) 145.9
pH (H2O) 7.8
SOC (g kg-1) 9.9
CEC (cmol(+) kg-1) 11.0
EC (µS cm-1)170.4
C/N ratio 7.6
BD (g cm-3) 1.3
Macronutrients
Total N (g kg-1) 1.3
Total S (g kg-1) 0.4
Available P (mg kg-1) 16.0
Exchangeable Mg (mg kg-1) 169.4
Exchangeable Ca (g kg-1) 0.9
Exchangeable K (mg kg-1) 82.8
Beneficial mineral elements
Exchangeable Na (mg kg-1) 164.3
Available Co (mg kg-1) 0.4
Total Al (g kg-1) 70.1
Micronutrients
Fe (g kg-1) 0.3
Mn (mg kg-1) 19.6
Cu (mg kg-1) 4.9
Zn (mg kg-1) 1.1
Ni (mg kg-1) 1.9
Mo (mg kg-1) 0.04
B (mg kg-1) 0.4
The standard deviation (SD) was always less than 10%.
L.G. ANGELINI ET AL.
8
Mg and Ca were equally distributed in the outer (bark) and the inner
(core) part of the stem.
As a general trend, significant differences were observed in the
macronutrient concentrations in each organ among the cultivars (Table
2). No effect due to the cultivar was observed in N concentration in the
core (2006), and S concentration in the core (2005), leaves and bark
(2006). Furthermore, for each cultivar, the allocation pattern observed
in each organ in the 1st year of cultivation, was not always maintained in
the following season. For instance, Red Petiole showed the highest leaf
N concentration in the 1st year and the lowest leaf N concentration in the
second one (Table 2).
The micronutrient and beneficial element concentrations in the three
plant organs are reported in Tables 3 and 4. In all the cultivars, Mn, Cu,
Zn, Mo, B, Na and Co showed the highest accumulation in the leaves,
followed by bark and core, whereas Fe, Ni and Al accumulated mainly
in the bark, followed by leaves and core. In general, there is little infor-
mation available on concentrations, patterns of distribution or the extent
of redistribution of micronutrients in hemp. The tendency of Fe, Ni and
Al to accumulate mainly in the bark could be related to the tendency of
other nutrients to accumulate (such as N, P, K, Mn, Mo, B and Na) or not
(such as S) in the same organ compared to the core. This may suggest the
existence of a synergistic/antagonistic relationship among the different
nutrients as already observed in other species (M et al., 2001).
Regarding to micronutrients (Table 3), the dioecious cultivar Red
Petiole showed the highest concentrations of Fe (in both years and in all
organs), Ni (in the second year and in all organs) and Zn (in both years,
in the leaves and bark) in comparison with the other cultivars. Fibranova
showed, in both years, the lowest Zn accumulation in the inner part of
the stem, while Carmagnola was characterised by the lowest Ni con-
centration in all the organs. Among the cultivar, the allocation of the
micronutrients in each organ was not stable between the two growing
seasons, as already observed for the macronutrients. For instance, C.S.
was characterized by the highest Cu concentration in the leaves and
core, but only in the 1st year. This pattern was not confirmed in the 2nd
year, being the monoecious Felina 34 the cultivar with the maximum
accumulation of this element in all plant organs. This cultivar showed,
at the same time, the lowest B concentrations in all organs (Table 3). In
relation to the beneficial elements (Na, Co, and Al), their concentrations
were significantly affected by the cultivar, with the exception of Na in
ACCUMULATION OF NUTRIENTS IN FIBRE HEMP CVS
9
T 2. – Macronutrient concentrations in plant organs (leaves, bark and core) of different cultivars of Cannabis sativa L.
Macronutrients (g kg-1)
Variety N S P Mg Ca K
Leaves Bark Core Leaves Bark Core Leaves Bark Core Leaves Bark Core Leaves Bark Core Leaves Bark Core
2005
Carmagnola 36.5ab 8.0bc 2.5b 0.32c 0.33a 0.31a 2.8ab 1.1b 0.2d 3.2b 0.5c 0.6bc 21.3a 3.2d 5.5a 23.2b 12.9c 4.4e
C.S. 37.4ab 12.4a 5.3a 0.39a 0.31ab 0.32a 2.2c 1.7a 0.5a 4.1a 0.5c 0.3d 20.6a 4.0ab 2.8d 20.0d 15.9ab 8.4a
Fibranova 36.9ab 7.8bc 3.3b 0.35b 0.32ab 0.32a 2.6b 1.1b 0.3c 3.3b 0.9a 0.6b 20.3a 4.1a 4.6bc 19.3d 11.8d 5.6d
Red Petiole 41.0a 9.8b 3.6b 0.31c 0.30b 0.31a 2.9ab 1.6a 0.3c 2.3c 0.6b 0.7a 20.9a 3.9b 5.1ab 24.4a 15.1b 6.1c
Felina 34 34.0b 6.4c 3.3b 0.35b 0.31ab 0.33a 3.2a 1.2b 0.4b 2.6c 0.5c 0.5c 16.9b 3.5c 4.3c 21.9c 16.4a 7.7b
Mean 2005 37.2A 8.9B 3.6C 0.35A 0.31A 0.32A 2.8A 1.4B 0.4C 3.1A 0.6B 0.5B 20.0A 3.7B 4.5B 21.8A 14.4B 6.5C
MS†5.32
*
1.26
***
0.38
**
1.010-4
***
1.010-4
*
6.010-5
n.s.
0.03
***
0.02
***
110-3
***
0.07
***
210-3
***
210-3
***
1.33
**
0.09
*
0.08
***
0.24
***
0.29
***
0.07
***
MS†† 4.24 *** 4.010-4 n.s. 0.08 *** 0.18 *** 1.43 *** 3.70 ***
2006
Carmagnola 32.7a 9.7a 3.0a 0.34a 0.30a 0.35ab 3.2b 1.9a 0.4c 3.3a 0.5c 0.6a 18.9b 3.3c 5.5a 26.5b 18.8c 5.0c
C.S. 29.6ab 8.3a 3.1a 0.33a 0.32a 0.33b 2.1d 1.1c 0.3d 3.2a 0.6b 0.3c 21.9a 3.5bc 3.0c 22.2c 19.5b 6.0b
Fibranova 29.3ab 9.4a 2.8a 0.34a 0.31a 0.34b 2.0d 1.0c 0.4c 2.3c 0.8a 0.6a 22.3a 3.8a 4.1b 15.1e 15.8d 5.4c
Red Petiole 27.1b 6.1b 2.8a 0.32a 0.32a 0.34b 3.5a 2.0a 0.6a 1.9d 0.5c 0.6a 21.2a 3.4bc 5.4a 30.0a 22.5a 6.1b
Felina 34 29.2ab 9.7a 3.1a 0.34a 0.30a 0.39a 2.4c 1.3b 0.5b 2.6b 0.6b 0.5b 18.3b 3.7ab 4.1b 18.3d 22.3a 8.5a
Mean 2006 29.6A 8.6B 3.0C 0.33A 0.31B 0.35A 2.7A 1.5B 0.5C 2.7A 0.6B 0.5B 20.5A 3.6B 4.4B 22.4A 19.8B 6.2C
MS†3.16
*
0.39
***
0.11
n.s.
1.410-4
n.s.
2.210-4
n.s.
4.010-4
*
0.01
***
0.01
***
110-3
***
0.02
***
210-3
***
210-3
***
0.41
***
0.03
***
0.07
**
0.52
***
0.09
***
0.07
***
MS†† 2.09 *** 2.410-4 ** 0.23 *** 0.11 *** 1.45 *** 15.28 ***
Means followed by the same letters are not significantly different at 0.05 probability level (LSD test) according to the one way ANOVA test. Upper-case letter, effect of plant organ; lower-case letter, effect of cultivar.
† Mean square (MS) from one-way completely randomised ANOVA with cultivar as variability factor.
†† Mean square (MS) from one-way completely randomised ANOVA with plant organ as variability factor.
*, **, *** and n.s., significant at P ≤ 0.05, P ≤ 0.01, P ≤ 0.001and not significant according to ANOVA analysis.
L.G. ANGELINI ET AL.
10
T 3. – Micronutrient concentrations in plant organs (leaves, bark and core) of different cultivars of Cannabis sativa L.
Micronutrients (mg kg-1)
Variety Fe Mn Cu Zn Ni Mo B
Leaves Bark Core Leaves Bark Core Leaves Bark Core Leaves Bark Core Leaves Bark Core Leaves Bark Core Leaves Bark Core
2005
Carmagnola 255.0a 330.0c 112.3b 25.7ab 15.1c 6.3c 9.9a 5.0c 3.7b 33.7a 10.5ab 9.7b 2.3c 12.9c 1.9d 2.4a 1.7a 1.5a 83.3a 26.3a 14.7b
C.S. 193.3c 632.7b 107.0b 28.3a 18.0a 4.7d 10.5a 4.2cd 7.5a 31.7a 8.3c 11.7a 3.0b 12.6c 3.2a 1.6b 1.4a 1.2b 86.7a 22.0b 15.7b
Fibranova 224.3b 649.0b 148.3a 22.3bc 15.1c 6.7bc 7.3c 8.8a 2.6c 26.3b 8.6bc 5.6d 7.3a 13.4b 2.2c 2.4a 1.2a 0.6c 64.0b 26.3a 11.7c
Red Petiole 232.7ab 863.7a 170.7a 24.3abc 15.9b 9.2a 9.0ab 3.4d 3.2bc 32.3a 12.0a 7.1c 1.8d 17.7a 2.8b 2.7a 1.3a 0.8c 53.3c 29.7a 19.0a
Felina 34 237.3ab 884.7a 65.3c 19.3c 14.8c 7.3b 7.4bc 6.5b 2.6c 26.0b 8.3c 6.2cd 3.2b 13.6b 2.4c 1.4b 1.1a 0.7c 37.7d 15.7c 9.7c
Mean 2005 228.5B 672.0A 120.7C 24.0A 15.8B 6.8C 8.8A 5.6B 3.9C 30.0A 9.5B 8.0B 3.5C 14.1A 2.5B 2.1A 1.4B 1.0C 65.0A 24.0B 14.1C
MS†275.50 * 2840
***
189.90
***
9.12
*
0.09
***
0.28
***
0.76
**
0.21
***
0.16
*** 5.66 ** 1.29
**
0.43
***
0.07
***
0.06
***
0.03
***
0.12
**
0.07
n.s.
0.03
***
12.48
***
4.23
***
2.26
***
MS†† 17470 *** 5.32 *** 3.62 ** 7.37 *** 3.15 * 0.17 ** 152.80 ***
2006
Carmagnola 190.3b 341.3c 108.7b 23.3b 20.0a 9.2ab 9.6ab 4.6b 2.0c 30.3b 11.3a 10.7a 1.7c 14.7abc 1.8c 2.0b 1.7ab 1.4a 72.3a 27.3bc 16.3b
C.S. 222.3a 352.3c 143.3a 28.7a 15.3b 5.6c 7.9bc 4.2bc 3.9b 35.0ab 12.3a 11.3a 2.3bc 16.3ab 1.9bc 2.0b 2.0a 1.4a 63.3b 22.7cd 16.3b
Fibranova 149.3c 530.3b 135.7a 24.3b 16.0ab 6.8c 7.8c 6.9a 3.4b 28.0b 11.0a 5.3d 2.7bc 13.7bc 2.2ab 2.6a 1.3bc 1.0ab 68.7ab 33.3ab 11.7b
Red Petiole 222.7a 790.7a 152.7a 28.3a 16.0ab 10.0a 8.4abc 3.6c 5.4a 40.0a 12.7a 8.3b 5.4a 18.0a 2.3a 2.0b 1.2c 0.7b 65.3b 39.0a 21.7a
Felina 34 179.7b 812.7a 88.7b 22.7b 17.7ab 7.3bc 9.7a 7.1a 6.4a 28.3b 10.3a 7.0c 3.4b 12.3c 2.2ab 2.7a 1.8a 1.1ab 41.3c 18.3d 13.0b
Mean 2006 192.9B 565.5A 125.8B 25.5A 17.0B 7.8C 8.7A 5.3B 4.2B 32.3A 11.5B 8.5C 3.1B 15.0A 2.1B 2.3A 1.6B 1.1C 62.2A 28.1B 15.8C
MS†81.72
***
4612
***
179.30
**
1.53
*
5.74
*
1.48
***
0.52
*
0.17
***
0.41
***
18.53
*
2.87
n.s.
0.47
***
0.41
***
4.46
*
0.05
*
0.01
***
0.07
*
0.07
*
9.79
***
11.65
***
7.28
**
MS†† 17980 *** 4.88 *** 2.15 ** 11.1 *** 2.35 * 0.11 *** 76.09 ***
Means followed by the same letters are not significantly different at 0.05 probability level (LSD test) according to the one way ANOVA test. Upper-case letter, effect of plant organ; lower-case letter, effect of cultivar.
† Mean square (MS) from one-way completely randomised ANOVA with cultivar as variability factor.
†† Mean square (MS) from one-way completely randomised ANOVA with plant organ as variability factor.
*, **, *** and n.s., significant at P ≤ 0.05, P ≤ 0.01, P ≤ 0.001and not significant according to ANOVA analysis.
ACCUMULATION OF NUTRIENTS IN FIBRE HEMP CVS
11
the bark (2006), Co in the bark (2005 and 2006) and in the core (2006).
Fibranova showed the lowest Na values in all organs in 2005 and only
in the core in 2006 (Table 4). The maximum Al accumulation was reg-
istered in Red Petiole in both years and in all organs.
The observed differences in macro- and micronutrient concentration
between bark and core might be related to the different anatomy of the
stem. The bark and core are, respectively, the stem tissues outside and
inside the vascular cambium and contain both long coarse fibres (pri-
mary bast fibres associated with the phloem bundle) and short fine fibres
(secondary bast fibres-attached to woody core). In general, the bark and
core of hemp differ in fibre length and chemical composition (i.e. cel-
lulose, hemicellulose and lignin) and, consequently, in percentage value
(V W et al., 1994). Thus, the chemical composition might be
connected with the different allocation of macro- and micronutrients in
the two stem organs.
Crop yield, nutrient uptake and partitioning. – The total dry bio-
mass yield, and the total macro- and micronutrient uptake, are reported
in Table 5. Our results confirmed the high nutrient requirements of
fibre hemp as already reported (I and I, 1996; B and
K, 1998), due to a large amount of dry yield produced (23.1 and
19.7 Mg ha-1 in 2005 and 2006 respectively, as overall mean among
the cultivars) in a relatively short vegetative period (110-115 days from
emergence to harvest). In the 1st year of cultivation, the dioecious cul-
tivars Carmagnola and Red Petiole showed the highest biomass yield,
while the monoecious Felina 34 was characterised by the lowest total
dry production (Table 5). In the 2nd year no significant differences were
observed among the dioecious cultivars that showed higher dry yield
values than the monoecious Felina 34. It is important to highlight that
there was a high removal of N, K and Ca, followed by P, Mg and S with
biomass harvesting (Table 5). Under the present conditions, independ-
ently from the cultivar and growing season, hemp requires 11.3 kg N,
1.2 kg P, 12.3 kg K, 0.33 kg S, 1.1 kg Mg and 7.7 kg Ca to produce 1
Mg dry yield. These values were similar to those found for macronutri-
ents by K and T (2003) and lower than those reported by
I and I (1996) in central Europe. Red Petiole had, in 2005,
the highest N, P, K and Ca uptakes. This trend was kept on the follow-
ing year except for nitrogen. Carmagnola was characterised by a greater
uptake of S, Mg and Ca than the other cultivars, in both years. The mon-
oecious Felina 34 showed the highest requirement of N, P and K per unit
L.G. ANGELINI ET AL.
12
Table 4. – Beneficial mineral elements concentrations in plant organs (leaves, bark
and core) of different cultivars of Cannabis sativa L.
Beneficial Mineral Elements (mg kg-1)
Variety Na Co Al
Leaves Bark Core Leaves Bark Core Leaves Bark Core
2005
Carmagnola 478.0a 326.3a 196.7b 1.9a 0.5a 0.4b 18.0a 17.3b 11.1ab
C.S. 422.3b 291.0b 265.3a 2.1a 0.5a 0.5b 12.5b 18.3ab 10.2ab
Fibranova 251.0d 262.3bc 131.0c 2.1a 0.4a 1.8a 17.3a 18.9ab 10.7ab
Red Petiole 319.3c 262.3bc 222.3ab 2.0a 0.4a 0.4b 19.0a 22.4a 11.8a
Felina 34 430.7ab 230.3c 213.7b 0.9b 0.4a 0.5b 17.2a 20.8ab 9.3b
Mean 2005 380.3A 274.5B 205.8C 1.8 A 0.5 B 0.7B 16.8B 19.5A 10.6C
MS†692.20
***
351.70
**
641.50
**
0.02
***
0.01
n.s.
0.12
**
0.58
***
0.56
***
0.19
***
MS†† 408.70 ** 0.21 *** 3.78 ***
2006
Carmagnola 403.0b 261.7a 234.3b 1.2b 0.6a 0.3a 12.9bc 17.3c 11.7a
C.S. 436.0a 262.7a 276.0a 1.2b 0.5a 0.2a 15.5ab 18.1bc 12.6a
Fibranova 381.7b 261.7a 138.7d 2.1a 0.6a 0.3a 11.6c 19.2ab 12.0a
Red Petiole 400.7b 230.0a 207.3bc 2.0a 0.5a 0.4a 16.8a 19.1ab 11.7a
Felina 34 378.7b 257.7a 191.3c 2.3a 0.5a 0.4a 12.2c 19.3a 9.8b
Mean 2006 400.0A 254.7B 209.5C 1.8A 0.6B 0.3C 13.8B 18.6A 11.6C
MS†315.30
***
464.80
n.s.
455.91
***
0.06
***
0.01
n.s.
0.01
**
0.51
***
0.41
*
0.35
**
MS†† 1106 *** 0.10 ** 2.69 ***
Means followed by the same letters are not significantly different at 0.05 probability level (LSD test) according to the
one way ANOVA test. Upper-case letter, effect of plant organ; lower-case letter, effect of cultivar.
† Mean square (MS) from one-way completely randomised ANOVA with cultivar as variability factor.
†† Mean square (MS) from one-way completely randomised ANOVA with plant organ as variability factor.
*, **, *** and n.s., significant at P ≤ 0.05, P ≤ 0.01, P ≤ 0.001and not significant according to ANOVA analysis.
of dry yield produced (13.6 kg N, 1.4 kg P, 14.7 kg K per Mg dry yield)
in comparison with the other dioecious cultivars (10.9 kg N, 1.1 kg P,
11.8 kg K per Mg dry yield) (Table 5).
The micronutrients and beneficial elements are also essential for
hemp growth, but in a relatively small amount. Among the different
elements, there was a higher removal of Fe (5.5 kg ha-1) and Na (5.7 kg
ha-1), followed by B (0.6 kg ha-1), Zn, Al and Mn (about 0.3 kg ha-1),
Cu and Ni (0.1 kg ha-1), Mo (0.03 kg ha-1) and finally Co (0.02 kg ha-1)
with biomass harvesting (Table 5). A great variability in the micronutri-
ent uptakes and beneficial elements requirements was observed among
ACCUMULATION OF NUTRIENTS IN FIBRE HEMP CVS
13
Table 5. – Total yield (Mg ha-1), and macronutrient, micronutrient and beneficial mineral element uptakes (kg ha-1) of different cultivars
of Cannabis sativa L.
Macronutrient uptake Micronutrient and beneficial mineral elements uptake
Variety Total
yield N P K S Mg Ca Fe Mn Cu Zn Ni Mo B Na Co Al
2005
Carmagnola 27.6a 295.4b 25.6b 275.3c 8.7a 30.9a 230.8a 5.05c 0.33b 0.14b 0.41a 0.11c 0.04a 0.86a 7.73a 0.02b 0.38b
C.S. 22.7ab 316.5b 26.5b 287.3b 7.6c 27.5b 138.1c 5.52bc 0.29c 0.17a 0.35b 0.12b 0.03b 0.74b 6.94b 0.02b 0.28c
Fibranova 19.3c 216.3d 19.3c 191.6d 6.2e 24.3c 147.5bc 5.58bc 0.23d 0.10d 0.20d 0.12b 0.02c 0.50c 3.63d 0.03a 0.27c
Red Petiole 26.9a 346.2a 30.5a 317.8a 8.2b 28.7ab 222.7a 8.55a 0.37a 0.12c 0.36b 0.14a 0.03b 0.77b 6.75b 0.02b 0.41a
Felina 34 19.2c 258.2c 27.8b 270.3c 6.4d 22.3c 154.0b 5.93b 0.24d 0.10d 0.24c 0.10d 0.02c 0.38d 5.45c 0.01c 0.28c
MS†14.4
*
170.3
***
1.7
***
43.5
***
210-3
***
2.1
***
58.2
***
0.1
***
2.810-4
***
7.710-5
***
2.410-4
***
6.410-6
***
1.110-5
***
6.010-4
***
0.15
***
1.410-6
***
6.210-5
***
2006
Carmagnola 20.5a 209.5b 26.7b 254.2b 6.9a 21.9a 154.5ab 3.69d 0.29ab 0.08c 0.30ab 0.10b 0.03a 0.61ab 5.60b 0.01b 0.27d
C.S. 20.7a 185.0c 17.1e 252.2b 6.8a 18.1c 131.0c 4.34cd 0.25c 0.10b 0.32a 0.12a 0.03a 0.54b 6.20a 0.01b 0.30a
Fibranova 20.8a 212.3b 19.2d 220.1c 6.9a 20.3b 159.4a 5.42ab 0.27abc 0.11b 0.24c 0.12a 0.03a 0.62ab 4.70c 0.02a 0.29b
Red Petiole 19.7a 167.5d 30.0a 288.1a 6.5b 17.2c 160.4a 6.09a 0.30a 0.11b 0.31a 0.13a 0.02b 0.68a 4.96c 0.01b 0.28c
Felina 34 17.0b 233.6a 23.2c 258.3b 6.0c 21.3ab 151.3b 5.01bc 0.26bc 0.13a 0.26bc 0.09b 0.03a 0.41c 4.62c 0.02a 0.22e
MS†3.21* 99.4
***
0.2
***
23.5
***
210-2
**
0.8
***
21.3
***
0.2
***
3.610-4
*
6.310-5
***
5.810-4
**
1.310-4
**
1.010-5
**
6.210-3
***
0.1
***
1.710-7
***
2.910-5
***
† Mean square (MS) from one-way completely randomised ANOVA with cultivar as variability factor.
*, ** and ***, significant at P ≤ 0.05, P ≤ 0.01 and P ≤ 0.001 according to ANOVA analysis.
L.G. ANGELINI ET AL.
14
the cultivars in both experimental years (Table 5). The micronutrients
required to produce one unit of dry biomass changed among the culti-
vars in the two years. For instance, Carmagnola showed the lowest Fe
need, while Red Petiole the highest one in both years. Felina showed
the lowest B requirement per unit of biomass produced (0.022 kg/Mg
dry yield averaged over the years), while Fibranova showed the lowest
Na need (0.21 kg/Mg dry yield averaged over the years). As regards to
the nutrient partitioning within the plant, the contribution of the differ-
ent plant organs significantly varied in function of the cultivar and the
mineral element considered (Fig. 1). As general trend, the leaves were
responsible of the major removal of N (66% of the total plant uptake),
P (53%), Mg (59%), Ca (58%), Mn (42%), Zn (50%), B (50%) and Co
(52%). Most Fe and Ni were mainly removed by the outer part of the
Fig. 1. – Contribution to the overall macronutrient, micronutrient and beneficial elements uptake by the dif-
ferent plant organs of the five hemp cultivars during the two growing seasons. *, **, *** and n.s., significant
at P ≤ 0.05, P ≤ 0.01, P ≤ 0.001and not significant according to ANOVA analysis.
ACCUMULATION OF NUTRIENTS IN FIBRE HEMP CVS
15
stem (54% and 63% respectively), while the core removed mainly S
(54%), Na (42%) and Al (43%). The other elements (K, Cu, Mo) were
up-taken, more or less, equally by the three organs.
The high variability in the nutrient requirements and their differ-
ent accumulation in the different plant organs of the five cultivars here
studied could be related to several factors: the different availability of
the mineral elements in the soil solution and their reciprocal chemical
interactions; the degree which nutrients are taken up by the roots; the
kind of plant organ or tissue; the mobility of the elements within the
plant; the climatic fluctuations over time. All together these factors may
become determining in the allocation of the mineral elements within the
plant throughout its vegetation period (B and B, 1988). In
case of leaf organ, all the nutrient levels are generally in accordance with
the proposed guidelines for hemp by B (1993) and by I
(2011) to avoid imbalances of nutrients (disease and injury for either
deficiencies or excesses).
C. – Our results outlined a significant effect of the culti-
var and kind of organ on the macro- and micronutrient concentration of
fibre hemp. In all the cultivars and years, the macronutrients accumulated
mainly in the leaves. The different parts of the stem (bark and core),
showed significant variations in macronutrient allocations: the concentra-
tion of N, P, and K in the bark was significantly higher than in the core,
while Mg and Ca were equally distributed in the outer (bark) and the
inner (core) part of the stem. Also the micronutrients, Mn, Cu, Zn, Mo, B,
and the beneficial elements, Na and Co, showed the highest accumulation
in the leaves, followed by bark and core. On the other hand, Fe, Ni and Al
accumulated mainly in the bark, followed by leaves and core.
It was possible to observe differences in the nutrient concentrations
among the cultivars between the two growing seasons. This was probably
due to the weather fluctuations over time – in particular the rainfall amount
and distribution – which might have influenced the availability of the min-
eral elements in the soil solution and their reciprocal chemical interactions.
The nutrient uptake and partitioning within the plant were prima-
rily dependent on cultivar characteristics in term of total dry yield and
yield components. The macronutrients were required by hemp cultivars
in relatively large amounts, above all N, K and Ca, followed by P, Mg
and S. The monoecious Felina 34 showed the highest requirement of N,
P and K per 1 Mg of dry yield produced, in comparison with the other
L.G. ANGELINI ET AL.
16
dioecious cultivars.
Among the micronutrient elements – which were also essential for
plant growth but in lower amounts – there was a higher removal of Fe
and Na followed by B with biomass harvesting. A great variability in the
micronutrient uptake was observed among the cultivars in both experi-
mental years.
Although it is difficult to estimate optimum fertilizer application ex
ante for fibre hemp cultivars, which are dependent by the site-specific
crop yield response, crop rotation, soil nutrient availability, etc., this
study represents the first effort to investigate nutrient allocation in dio-
ecious and monoecious fibre hemp cultivars in order to achieve accept-
able yields, minimizing the environmental impact of their cultivation. A
correct fertilisation and, consequently, the reduction of the costs associ-
ated with it, could become an important tool for making more sustain-
able this multipurpose crop. Although hemp requires high amounts of
macronutrients, most of them can return to the soil in a significant level
through the above-ground biomass, as well as by the taproots. In the
same way, approximately one third of the total K required by the crop,
can be returned to the soil through the inner part of the stem, in the case
of field retting. For these interesting features, hemp could be used in the
crop rotations to stabilise nutrient levels and to improve soil properties.
A. – Seeds of the five hemp cultivars were
kindly provided by Dr. Mario Di Candilo from CRA-CIN (Bologna,
Italy). The authors wish to thank to Dr. Rita Aromolo for her helpful
and skilful technical assistance during the laboratory analysis at CRA-
RPS. Dr. Sabrina Tozzi is also gratefully acknowledged for her help in
collecting data from the field experiment.
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