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American Journal of Biology and Life Sciences
2018; 6(3): 36-43
http://www.openscienceonline.com/journal/ajbls
ISSN: 2381-3784 (Print); ISSN: 2381-3792 (Online)
Effect of NPK Fertilization on the Growth, Yield,
Quality and Mineral Nutrition of New Sweet Plant in
Morocco (
Stevia rebaudiana
Bertoni)
Abderrahmane Benhmimou
1, 2, *
, Mohammed Ibriz
1
, Ahmed Douaik
2
, Mounira Lage
2
, Chaouki Al Faïz
2
,
Soukaina Chaouqi
1
, Abdelmjid Zouahri
2
1
Faculty of Sciences, Ibn Tofail University, Kenitra, Morocco
2
Regional Center of Agricultural Research, National Institute of Agricultural Research, Rabat, Morocco
Email address
*
Corresponding author
To cite this article
Abderrahmane Benhmimou, Mohammed Ibriz, Ahmed Douaik, Mounira Lage, Chaouki Al Faïz, Soukaina Chaouqi, Abdelmjid Zouahri.
Effect of NPK Fertilization on the Growth, Yield, Quality and Mineral Nutrition of New Sweet Plant in Morocco (Stevia rebaudiana
Bertoni). American Journal of Biology and Life Sciences. Vol. 6, No. 3, 2018, pp. 36-43.
Received: May 3, 2018; Accepted: June 24, 2018; Published: July 26, 2018
Abstract
Stevia (Stevia rebaudiana Bertoni) is an herbaceous perennial plant of the Asteraceae family, originating from the Amambay
region in the north-east of Paraguay, where it grows wild in sandy soils. Dry leaves are the economic part of the stevia plant,
with a high concentration of steviol glycosides, which are many times sweeter than sugarcane and sugarbeet but importantly
without any calories. Fertilizer requirement for stevia is moderate and varies according to the environment and soil type. Due
to the short time of stevia introduction as a new crop in Morocco, there is no information available on nutrient requirement.
The aim of the present work is to determine the optimum nitrogen (N), phosphorus (P), and potassium (K) levels for higher dry
leaf yield and steviol glycosides content and their accumulation in stevia in north-western Moroccan conditions. The
experiment consisted of 27 fertilization treatments combinations of N (100, 200, and 300 kg ha
-1
), P (50, 100, and 150 kg ha
-1
),
and K (80, 160, and 240 kg ha
-1
) and a control treatment, each in three replicates. The results indicated that significantly higher
fresh biomass yield, fresh and dry leaf yield, and total steviol glycosides yield were obtained with T24 treatment (300N, 100P,
240K) (96.53, 69.87, 19.56, and 2.13 g plant
-1
, respectively). Also, T24 led to higher N content (1.81%) than the control
(0.40%). However, higher P and K contents were obtained with T25 (300N, 150P, 80K) and T3 (100N, 50P, 240K) treatments,
respectively. The growth parameters viz., plant height and stem diameter were significantly higher with T16 treatment (200N,
150P, 80K) while, the stevioside and total steviol glycoside contents were higher in T6 (100N, 100P, 240K) stevia leaves. The
T24 could be considered as an economically optimum level of nutrients for stevia.
Keywords
Stevia, Steviol Glycosides, Nitrogen, Phosphorus, Potassium, Dry Leaf, Yield
1. Introduction
Stevia (Stevia rebaudiana Bertoni) is an herbaceous
perennial plant of the Asteraceae family, originating from the
Amambay region in the north-east of Paraguay, where it
grows wild in sandy soils near streams on the edges of
marshland, acid infertile sand or muck soils [24]. Dry leaves
are the economic part of the stevia plant [37], with a high
concentration of steviol glycosides (SG), possible substitutes
of synthetic sweeteners [39] which are many times sweeter
than sugarcane and sugarbeet but importantly without any
calories [8]. The main SG in stevia leaf are stevioside (STV)
(5–10% of dry leaf weight), which is about 300 times sweeter
than sucrose [11] and rebaudioside A (Reb A) (2–4%), which
is more suited than STV for use in foods and beverages due
to its pleasant taste [44]. Commercial exploitation of stevia
started in 1970 in Japan [36] and then extended to China,
37 Abderrahmane Benhmimou et al.: Effect of NPK Fertilization on the Growth, Yield, Quality and Mineral Nutrition of
New Sweet Plant in Morocco (Stevia rebaudiana Bertoni)
Brazil, Paraguay, Mexico, Russia, Indonesia, Korea, USA,
India, Tanzania, Canada and Argentina [32]. European
regulatory bodies including the joint FAO/WHO Expert
Committee on Food Additives (JECFA) and the European
Food Safety Authority (EFSA) have now agreed that SG is
safe for all populations to consume and is a suitable
sweetening option for diabetics. Effective from December
2
nd
, 2011, the EU has approved it use as a food additive [12].
Stevia is relatively unknown in Morocco, where it can be a
new sweet crop [1].
The amount of SG depends on total biomass yield, which
further depends on the climate and agro-techniques [19],
[20]. Among the agro-techniques, reliable nutrient supply is
the most important factor for higher crop yield. Among the
17 essential plant nutrients, N, P and K are the most often
limiting macronutrients for plant growth and development.
Nitrogen is an essential element of key macro-molecules
such as proteins, nucleic acids, some lipids, and chlorophylls
[34]. Phosphorus is also a component of nucleic acids,
phospholipids, and ATP [41]. Potassium, third most essential
macronutrient of plant, plays a central role in many
fundamental metabolic processes, such as turgor driven
movements, osmoregulation, control of membrane
polarization and protein biosynthesis [10]. Thus, plants
cannot perform properly without a reliable supply of these
nutrients. Moreover, high dose fertilizer mainly N is harmful
for soil health, especially when applied above the economic
optimum dose.
Nutritional requirements for stevia are low to moderate
[14] since this crop is adapted to poor quality soils in its
natural habitat at Paraguay. While, [15] reported that
nutritional dose varies according to the environment and soil
type. Under average climatic conditions and soil type 70 kg
Nitrogen, 35 kg Phosphorus and 45 kg potassium per hectare
is recommended [43]. [32] have earlier studied the interactive
effects of crop ecology and plant nutrition on yield and
secondary metabolites of stevia in northern India. [3], have
studied the effect of nitrogen, phosphorus and potassium
levels on growth and yield of stevia in medium black, clayey
soil under south of India. It was shown that the application of
foliar nutrients led to an increase in chlorophyll, nitrogen,
and potassium content in leaves but not in SG content [33].
Due to the short time of stevia introduction as a new crop in
Morocco, there is no information available on nutrient
requirement. The aim of the present work is to determine the
optimum nitrogen (N), phosphorus (P), and potassium (K)
levels for higher dry leaf yield and SG content and their
accumulation in stevia in north-western Moroccan
conditions.
2. Materials and Methods
2.1. Study Location
The study was carried out during stevia growing period
from 25
th
March to 17
th
August, 2014 in the Regional Centre
of Agronomic Research of Rabat in Morocco (INRA) (34.21
N, 6.40 E, 10.5 m above mean sea-level). The location
(Rabat) represents the sub humid region of north-western
Morocco, with mean maximum temperature of 27.1°C in
August and mean minimum of 8°C in January. The average
annual rainfall received is about 554 mm, of which about 74
percent is received during November to March. During the
crop growth period daily maximum temperature ranged from
26.3 to 28.2°C, the minimum temperature ranged from 14.8
to 18.3°C and the mean relative humidity ranged between
66.8–86.6%. Total rainfall received during the crop growth
season was 4.6 mm. These climatic data were measured at a
height of 2 m by an automatic weather station (iMETOS,
Pessl Instruments, Austria), located near the experimental
site.
2.2. Experimental Design and Treatments
The selected seed for that experiment belongs to the
INRA variety. The sowing was performed into plug trays
filled with land and commercial substrate on March 25
th
,
2014 and watered to field capacity (FC) by tap water in the
greenhouse. Two-month-old the uniform seedlings were
transplanted in the plastic pots on May 27
th
, 2014, with two
plants per pot. The 10 L pots were filled with 1 kg of gravel
at the bottom for drainage and 6 kg of sandy soil. Before
application of mineral fertilizers. The soil was analysed in
the laboratory of Research Unit on Environment and
Conservation of Natural Resources INRA, RCAR of Rabat.
The soil contained 5.1% clay, 11.7% silt, and 80.8% sand.
The organic matter content was 2.5%, the pH was 8.15 and
the N, P, and K contents were 39.7, 7.6, and 20.3 ppm,
respectively. Soil moisture at field capacity was 13.44% and
soil moisture at permanent wilting point was 4.71%. Soil
density (ρ) was 1.4 g cm
-3
, which used to convert doses of
NPK from kg ha
-1
to g pot
-1
. All pots were placed in open
field and irrigated near the field capacity since this
experiment was conducted during stevia growing season.
The experiment consisted of 27 fertilization treatments
combinations comprising three levels of N (100, 200, and
300 kg ha
-1
), three levels of P (50, 100, and 150 kg ha
-1
),
and three levels of K (80, 160, and 240 kg ha
-1
) and a
control treatment without any nutrients, each in three
replicates totalling 84 experimental pots arranged according
to a randomized complete block design. Details of
treatments are shown in the tables 1, 2 and 3. The NPK
fertilizers were applied in the form of ammonium nitrate
(33% N), triple superphosphate (45% phosphorus pentoxide
(P
2
O
5
)), and muriate of potash (50% potassium oxide
(K
2
O)), respectively. A half dose of N and full dose of P
and K as per treatment were applied at the time of
transplanting, while remaining half dose of N was applied
at 45 days after transplanting. The plants of the whole pots
were harvested manually 10 cm above the base of the stem
[27] at 85 days after transplanting on August 17
th
, 2014,
when the concentration of steviol glycoside is maximum
[7]. Leaves and stems were separated and used for further
data analysis.
American Journal of Biology and Life Sciences 2018; 6(3): 36-43 38
2.3. Growth and Yield Analysis
Plant height and stem diameter of stevia plants were
recorded at harvest. The plant height was measured with a
meter ruler from ground to the base of the fully opened leaf
and the stem diameter was measured with slide calipers up to
0.01 mm accuracy. Biomass yield (total fresh leaf and stem
yield), fresh leaf yield, and dry leaf yield were determined in
each plant. We estimated the fresh biomass, fresh and dry
leaf yield per plant using one digital scale with precision of
0.01 g. Leaves were dried at 50°C temperature in hot air
dryer for 6 hours and stored in clean gunny bags. At this
temperature, the quality of dried leaves produced, in terms of
colour, sweetness and nutrient content, was better compared
with drying at 70°C [40]. Dry leaf had an important role in
stevia extract in term of quality [48].
2.4. Determination of NPK in Leaf
After recording growth and yield data, the dried stevia leaf
samples were prepared with a laboratory grinder having a
sieve spacing of 2 mm to determine nitrogen, phosphorus,
and potassium content in the leaf. Total nitrogen content was
determined by using the Macro Kjeldahl digestion and
distillation method [35], while total phosphorus and
potassium were determined using a colorimetric method [31]
and flame photometer (model CL378) [46], respectively.
2.5. Steviol Glycosides Analysis
For determination of steviol glycosides for all plants, dry
leaves of stevia obtained during this experiment were ground
in a laboratory grinding mill to produce powder particles of
0.10 mm in size, and were kept at ambient temperature until
they were used for the analysis to assess the contents of
stevioside (STV), rebaudioside A (Reb A) and total steviol
glycosides (STV; Reb, A, B, C, D and F; steviolbioside;
rubudioside and dulcoside A) as influenced by NPK
fertilizers. STV (%), Reb A (%) and total SG (%) were
determined in the powdered stevia leaves sent to the STEVIA
NATURA Company of France. The SG yield was estimated
by multiplying dry leaves yield by the content of SG in
leaves.
2.6. Statistical Analysis
Data obtained were analyzed by the analysis of variance
(ANOVA) using Statistical Analysis System ver. 9.1 (SAS
Institute Inc., Cary, NC., USA), and means were compared
using Duncan’s multiple range test (DMRT) at the 0.05
significance level.
3. Results
3.1. Growth and Yield Parameters
The mean data on plant height, stem diameter, fresh
biomass yield, fresh leaf yield, and dry leaf yield are
presented in table 1. These parameters were significantly
influenced by the interaction effects of different levels of
nitrogen (N), phosphorus (P) and potassium (K) compared to
the control. Treatment T16 (200:150:80 kg ha
-1
NPK)
remained statistically at par with T5 (100:100:160 kg ha
-1
NPK) but recorded significantly higher plant height (71 cm)
than remaining treatments and absolute control (30 cm). T16
and T5 recorded 57.75 percent and 56.93 percent higher plant
height as compared to the control, respectively. Stem
diameter data also followed the same trend as plant height.
Highest stem diameter (9.59 mm) was possible with T16
which was on par with T4 (100:100:80 kg ha
-1
NPK) and
both were significantly higher as compared to all other
treatments and control (4.88 mm). T16 recorded 49.11
percent higher stem diameter as compared to the control.
Treatment T24 (300:100:240 kg ha
-1
NPK) produced
significantly greater fresh biomass yield at harvest (96.53 g
plant
-1
) as compared to remaining treatments and control
(17.70 g plant
-1
). Likewise, fresh leaf yield and dry leaf yield
were also significantly greater in the T24 treatment (69.87
and 19.56 g plant
-1
, respectively) as compared to all other
treatments and the control (11.43 and 3.33 g plant
-1
,
respectively). The control significantly decreased fresh
biomass yield, fresh leaf yield, and dry leaf yield until
81.66%, 83.64%, and 82.97%, respectively, compared to
T24.
Table 1. Effect of NPK fertilization on growth and yield parameters of stevia.
Treatment Parameters
Plant height (cm) Stem diameter (mm) Fresh biomass (g plant
-
1
) Fresh leaf (g plant
-
1
) Dry leaf (g plant
-
1
)
T0 30.00o 4.88o 17.70m 11.43m 3.33o
T1 33.67n 5.49n 27.68k 17.62kl 5.07mn
T2 50.00l 6.29lm 22.42l 13.51m 3.35o
T3 48.33l 7.41efghi 25.56kl 13.65m 4.26no
T4 48.33l 9.59a 35.16ij 18.66kl 6.91k
T5 69.67a 8.45bc 42.37h 20.77k 6.33kl
T6 48.67l 6.75kl 29.12k 17.37l 5.15mn
T7 48.67l 5.86mn 27.52k 19.74kl 5.91lm
T8 58.33fgh 7.98cde 37.54i 26.57j 6.99k
T9 59.67def 7.34fghij 84.58b 48.73d 12.56def
T10 62.67bc 8.35bc 62.33ef 41.81f 10.90h
T11 50.67kl 7.20hij 53.69g 35.33h 11.65fgh
T12 51.00kl 7.50efgh 52.53g 39.52fg 13.88c
T13 53.33jk 7.70defg 59.92f 42.27f 12.74de
T14 45.33m 6.98ijk 33.69j 28.03ij 8.69j
39 Abderrahmane Benhmimou et al.: Effect of NPK Fertilization on the Growth, Yield, Quality and Mineral Nutrition of
New Sweet Plant in Morocco (Stevia rebaudiana Bertoni)
Treatment Parameters
Plant height (cm) Stem diameter (mm) Fresh biomass (g plant
-
1
) Fresh leaf (g plant
-
1
) Dry leaf (g plant
-
1
)
T15 51.33kl 8.37bc 53.06g 39.21fg 11.53fgh
T16 71.00a 9.59a 51.10g 27.72ij 9.01ij
T17 64.33b 8.20cd 52.79g 35.37h 9.77i
T18 62.00bcd 7.97cdef 63.27def 39.60fg 12.54def
T19 55.67hij 7.26hij 77.35c 53.98bc 13.23cd
T20 63.00bc 7.94cdef 60.49f 35.74h 12.36defg
T21 59.00efg 8.83b 54.62g 37.68gh 11.98efg
T22 56.33ghi 8.84b 84.45b 55.76b 16.99b
T23 60.33cdef 6.84jkl 37.27ij 30.18i 14.16c
T24 54.33ij 7.30ghij 96.53a 69.87a 19.56a
T25 58.33fgh 7.65defg 42.14h 27.60ij 8.77j
T26 61.33cde 8.05cde 65.27de 45.67e 11.45gh
T27 48.33l 7.71defg 66.54d 51.14cd 13.17cd
* Means followed by different letters in each column are significantly different (Duncan multiple range test at the 5% significance level).
T0 (Control), T1 (100:50:80 kg ha
-1
NPK), T2 (100:50:160 kg ha
-1
NPK), T3 (100:50:240 kg ha
-1
NPK), T4 (100:100:80 kg ha
-1
NPK), T5 (100:100:160 kg ha
-
1
NPK), T6 (100:100:240 kg ha
-1
NPK), T7 (100:150:80 kg ha
-1
NPK), T8 (100:150:160 kg ha
-1
NPK), T9 (100:150:240 kg ha
-1
NPK), T10 (200:50:80 kg ha
-1
NPK), T11 (200:50:160 kg ha
-1
NPK), T12 (200:50:240 kg ha
-1
NPK), T13 (200:100:80 kg ha
-1
NPK), T14 (200:100:160 kg ha
-1
NPK), T15 (200:100:240 kg
ha
-1
NPK), T16 (200:150:80 kg ha
-1
NPK), T17 (200:150:160 kg ha
-1
NPK), T18 (200:150:240 kg ha
-1
NPK), T19 (300:50:80 kg ha
-1
NPK), T20 (300:50:160
kg ha
-1
NPK), T21 (300:50:240 kg ha
-1
NPK), T22 (300:100:80 kg ha
-1
NPK), T23 (300:100:160 kg ha
-1
NPK), T24 (300:100:240 kg ha
-1
NPK), T25
(300:150:80 kg ha
-1
NPK), T26 (300:150:160 kg ha
-1
NPK), T27 (300:150:240 kg ha
-1
NPK).
3.2. Nutrient (NPK) Contents in Leaf
The effects of different combinations of NPK fertilization
on nitrogen, phosphorus, and potassium contents in dry leaf
of stevia are presented in table 2. All of the above parameters
were significantly influenced by different NPK combinations
compared to the control. Significantly higher nitrogen content
(1.81%) in dry leaf was recorded with 300:100:240 kg ha
-1
NPK (T24) as compared to all other treatments and absolute
control. The lowest nitrogen content was with the control
(0.40%). However, application of 300:150:80 kg ha
-1
NPK
(T25) recorded significantly higher phosphorus content
(1.18%) in dry leaf as compared to the control (0.08) and
other treatments. The combination of 100:50:240 kg ha
-1
NPK (T3) recorded significantly higher potassium content
(2.41%) in dry leaf as compared to the control (0.82) and
other treatments but remained statistically at par with T6
(100:100:240 kg ha
-1
NPK) and T18 (200:150:240 kg ha
-1
NPK). The potassium content was decreased in control stevia
dry leaf than T3, T6, and T18 (65.98%, 65.55%, and 65.40%,
respectively).
Table 2. Effect of NPK fertilization on NPK (%) content in dry leaf of stevia.
Treatment Parameters
Nitrogen (%) Phosphorus (%)
Potassium (%)
T0 0.40m 0.08k 0.82m
T1 0.86j 0.11i 1.21j
T2 0.91i 0.10j 1.80gh
T3 0.82k 0.12hi 2.41a
T4 0.79l 0.18fg 1.17k
T5 0.82k 0.16g 1.77h
T6 0.86j 0.17fg 2.38ab
T7 0.83k 0.22e 1.16k
T8 0.91i 0.24bcd 1.90f
T9 0.93i 0.23de 2.29de
T10 1.39e 0.10j 1.17k
T11 1.27g 0.11i 1.83g
T12 1.33f 0.12hi 2.36bc
T13 1.41e 0.19f 1.13kl
T14 1.25h 0.26b 1.78h
Treatment Parameters
Nitrogen (%) Phosphorus (%)
Potassium (%)
T15 1.28g 0.18fg 2.28e
T16 1.40e 0.25bc 1.15kl
T17 1.38e 0.24bcd 1.90f
T18 1.31f 0.23de 2.37abc
T19 1.68d 0.13h 1.13kl
T20 1.70cd 0.12hi 1.81gh
T21 1.72c 0.11i 2.30de
T22 1.69d 0.17fg 1.11l
T23 1.75b 0.17fg 1.70i
T24 1.81a 0.17fg 2.27e
T25 1.77b 1.18a 1.12kl
T26 1.69d 0.25bc 1.80gh
T27 1.75b 0.25bc 2.33cd
* Means followed by different letters in each column are significantly
different (Duncan multiple range test at the 5% significance level).
T0 (Control), T1 (100:50:80 kg ha
-1
NPK), T2 (100:50:160 kg ha
-1
NPK), T3
(100:50:240 kg ha
-1
NPK), T4 (100:100:80 kg ha
-1
NPK), T5 (100:100:160
kg ha
-1
NPK), T6 (100:100:240 kg ha
-1
NPK), T7 (100:150:80 kg ha
-1
NPK),
T8 (100:150:160 kg ha
-1
NPK), T9 (100:150:240 kg ha
-1
NPK), T10
(200:50:80 kg ha
-1
NPK), T11 (200:50:160 kg ha
-1
NPK), T12 (200:50:240
kg ha
-1
NPK), T13 (200:100:80 kg ha
-1
NPK), T14 (200:100:160 kg ha
-1
NPK), T15 (200:100:240 kg ha
-1
NPK), T16 (200:150:80 kg ha
-1
NPK), T17
(200:150:160 kg ha
-1
NPK), T18 (200:150:240 kg ha
-1
NPK), T19
(300:50:80 kg ha
-1
NPK), T20 (300:50:160 kg ha
-1
NPK), T21 (300:50:240
kg ha
-1
NPK), T22 (300:100:80 kg ha
-1
NPK), T23 (300:100:160 kg ha
-1
NPK), T24 (300:100:240 kg ha
-1
NPK), T25 (300:150:80 kg ha
-1
NPK), T26
(300:150:160 kg ha
-1
NPK), T27 (300:150:240 kg ha
-1
NPK).
3.3. Quality Parameters
Stevioside (STV) content (%) in stevia dry leaves was
significantly modified by different treatments of NPK
combinations (Table 3). Treatment T6 (100:100:240 kg ha
-1
NPK) recorded significantly higher STV content (10.80% of
the leaf dry weight) followed by T1 (100:50:80 kg ha
-1
NPK)
(8.20%) which was statistically on par with T20 (300:50:160
kg ha
-1
NPK) but recorded significantly higher STV content
than other treatments and unfertilized pot, while the lowest
content of STV (3.35%) was obtained with 100:100:160 kg
ha
-1
NPK (T5). Also, different treatments caused a significant
American Journal of Biology and Life Sciences 2018; 6(3): 36-43 40
effect on rebaudioside A (Reb A) content, total steviol
glycosides (SG) content and total SG yield (Table 3). Highest
total SG content (15.05%) was possible with T6 which was
on par with T1 and both were superior to remaining
treatments and control. Lower content of total SG (8.15%)
was observed in T17 (200:150:160 kg ha
-1
NPK). This
treatment recorded about 45.85% and 43.40% lower total SG
content in leaf compared with T6 and T1, respectively.
However, the maximum content of Reb A (5.60%) was
recorded with the application of 200:100:80 kg ha
-1
NPK
(T13) which was followed by T16 (200:150:80 kg ha
-1
NPK)
(4.55%) which was on par with T11 (200:50:160 kg ha
-1
NPK), T18 (200:150:240 kg ha
-1
NPK), and T21 (300:50:240
kg ha
-1
NPK) but recorded significantly higher Reb A content
as against all other treatments applied with nutrients and
control. T13 recorded about 82.14% higher Reb A content in
leaf compared with T20 (300:50:160 kg ha
-1
NPK) which
recorded lower content (1%). Though the highest value of
total SG yield (2.13 g plant
-1
) was obtained with 300:100:240
kg ha
-1
NPK (T24) as compared to other treatments and
control, while the lowest yield of total SG (0.34 g plant
-1
)
was obtained with the control and was on par with T2
(100:50:160 kg ha
-1
NPK) and T3 (100:50:240 kg ha
-1
NPK).
The total SG yield was decreased in control than T24
(84.04%).
Table 3. Effect of NPK fertilization on steviol glycosides of stevia.
Treatment Parameters
Stevioside (%) Rebaudioside A (%) Total SG (%) Total SG (g plant
-
1
)
T0 4.75efghij 2.60ghi 9.60jkl 0.34i
T1 8.20b 4.20bcd 14.40a 0.74h
T2 6.40cde 4.00bcde 11.60cdefg 0.40i
T3 6.55bcd 2.95fgh 10.85defghi 0.48i
T4 6.00cdefgh 3.20efg 10.35ghij 0.74h
T5 3.35j 3.45cdefg 10.75defghi 0.70h
T6 10.80a 2.75ghi 15.05a 0.79h
T7 6.70bcd 3.35defg 11.85bcdef 0.74h
T8 4.60fghij 4.10bcd 10.15hijk 0.71h
T9 5.05cdefghij 1.40jk 8.70lm 1.09g
T10 4.35hij 4.00bcde 9.90hijkl 1.09g
T11 5.15cdefghi 4.50b 11.15cdefgh 1.25defg
T12 4.65efghij 3.20efg 9.25jklm 1.31def
T13 5.35cdefghi 5.60a 13.00b 1.66b
T14 6.65bcd 1.95ij 9.70ijkl 0.87h
T15 6.30cdef 3.75bcdef 11.90bcde 1.39cd
T16 6.70bcd 4.55b 12.95b 1.20efg
T17 4.65efghij 2.20hi 8.15m 0.81h
T18 4.40ghij 4.45b 10.60efghi 1.33de
T19 6.15cdefg 4.00bcde 12.00bcd 1.65b
T20 6.80bc 1.00k 9.15jklm 1.15fg
T21 4.10ij 4.40b 11.05cdefgh 1.34de
T22 5.25cdefghi 2.65ghi 8.95klm 1.52bc
T23 6.15cdefg 3.45cdefg 10.70defghi 1.52bc
T24 5.00defghij 4.15bcd 10.65efghi 2.13a
T25 6.20cdef 4.25bc 12.20bc 1.10g
T26 5.05cdefghij 3.95bcde 10.55fghi 1.21efg
T27 6.10cdefgh 4.00bcde 11.65cdefg 1.53bc
* Means followed by different letters in each column are significantly different (Duncan multiple range test at the 5% significance level).
T0 (Control), T1 (100:50:80 kg ha
-1
NPK), T2 (100:50:160 kg ha
-1
NPK), T3 (100:50:240 kg ha
-1
NPK), T4 (100:100:80 kg ha
-1
NPK), T5 (100:100:160 kg ha
-
1
NPK), T6 (100:100:240 kg ha
-1
NPK), T7 (100:150:80 kg ha
-1
NPK), T8 (100:150:160 kg ha
-1
NPK), T9 (100:150:240 kg ha
-1
NPK), T10 (200:50:80 kg ha
-1
NPK), T11 (200:50:160 kg ha
-1
NPK), T12 (200:50:240 kg ha
-1
NPK), T13 (200:100:80 kg ha
-1
NPK), T14 (200:100:160 kg ha
-1
NPK), T15 (200:100:240 kg
ha
-1
NPK), T16 (200:150:80 kg ha
-1
NPK), T17 (200:150:160 kg ha
-1
NPK), T18 (200:150:240 kg ha
-1
NPK), T19 (300:50:80 kg ha
-1
NPK), T20 (300:50:160
kg ha
-1
NPK), T21 (300:50:240 kg ha
-1
NPK), T22 (300:100:80 kg ha
-1
NPK), T23 (300:100:160 kg ha
-1
NPK), T24 (300:100:240 kg ha
-1
NPK), T25
(300:150:80 kg ha
-1
NPK), T26 (300:150:160 kg ha
-1
NPK), T27 (300:150:240 kg ha
-1
NPK).
4. Discussions
Data on growth parameters clearly showed that different
treatments of NPK combinations had a significant effect on
the growth. In this study, all treatments increased growth
parameters as compared to absolute control. Maximum plant
height and stem diameter were attained by 200:150:80 kg ha
-
1
NPK. Differences in growth may be because of the higher
absorption of water and mineral nutrients due to extensive
colonization of roots [16]. [13] and [26] reported that N
stimulated the leaf production probably due to the increasing
production of cytokinin in root tips and their eventual export
to the shoot. The results are in accordance with the findings
of [3], who reported that plant height was significantly higher
with nitrogen, phosphorus, and potassium (400, 200, and 200
kg ha
-1
, respectively) which were on par with 300, 150, and
100 kg ha
-1
respectively. [9] also reported increased plant
height and number of branches plant
-1
with nutrient levels of
40:30:45 kg NPK ha
-1
in sandy loam soils at Bangalore.
Increased plant height and number of leaves plant
-1
with
41 Abderrahmane Benhmimou et al.: Effect of NPK Fertilization on the Growth, Yield, Quality and Mineral Nutrition of
New Sweet Plant in Morocco (Stevia rebaudiana Bertoni)
increased levels of N, P and K fertilizers was also reported by
[30] in India.
The higher fresh biomass, fresh leaf yield, and dry leaf
yield of stevia with higher levels of nitrogen (300 kg ha
-1
),
phosphorus (100 kg ha
-1
) and potassium (240 kg ha
-1
)
nutrient combination in the present study could be attributed
to more number of branches and leaves plant
-1
, and higher
leaf area plant
-1
. The higher dry leaf yield and biomass may
be also due to the supply of sufficient nitrogen, phosphorus
and potassium during the crop growth period. [6] reported
that P is an essential component of key molecules such as
nucleic acids, phospholipids, and ATP, which are necessary
for photosynthesis, energy transfer, carbohydrate, and protein
synthesis. A similar increase in dry leaf yield of stevia with
NPK combination was also reported by [3]. [38] showed that
stevia plants grown at 40 and 60 kg N ha
-1
produced
significantly higher dry leaf yield than at 0 and 20 kg N ha
-1
.
Increased dry leaf yield was also reported by [25] with
105:30:45 kg NPK ha
-1
as compared to lower doses of NPK
under loamy soil in Karnataka, India. Similarly, [23]
observed that shortly before or at flowering, production of 1
ton of dry leaves of stevia required 64.6 kg N ha
-1
, 7.6 kg P
ha
-1
and 56.1 kg K ha
-1
. [32] reported that the applications of
90 kg N, 40 kg P and 40 kg K ha
-1
are the best nutritional
conditions in terms of dry leaf yield for CSIR-IHBT (Council
of Scientific and Industrial Research- Institute Himalayan
Bioresource Technology) and RHRS (Regional Horticultural
Research Station) conditions. Significantly lower fresh
biomass, fresh leaf yield, and dry leaf yield were obtained
with the absolute control as against all other treatments
applied with nutrients, due to the lowest number of branches
and leaves plant
-1
. [29] in Japan experimentally proved that
no manuring resulted in lowest leaf yield of stevia. [42] also
reported lower dry leaf yield with absolute control without
any fertilizer, which was 62 and 63 per cent less as compared
to higher levels of nitrogen and phosphorous. In accordance
of our results yield of stevia increased significantly with
increasing rates of N, P and K up to 60:30:45 kg ha
-1
per crop
with the highest dry leaf yield which was on par with
40:20:30 kg ha
-1
per crop in sandy loam soils at Bangalore
[9]. [5] reported increased biomass and leaf yield due to the
application of higher levels of phosphorus and potassium, but
no significant effect of higher level of nitrogen in an Andosol
with a pH of 4.5 at Canada. Research conducted at Egypt
also showed a gradual and significant increase in fresh and
dry leaf biomass yields of stevia when nitrogen fertilizer was
increased from 10 to 30 kg N ha
-1
wherein the dry leaves
yield increased by 64 per cent compared to lower dose [4].
While, [22] reported increase in leaf yield with moderate
application of N, P and K fertilizers in Korea. There are,
however, reports that stevia crop shows yield reduction at
high rates of fertilizer.
Nitrogen, phosphorus, and potassium contents in stevia
leaf at harvest were significantly influenced by the levels of
N, P, and K. The contents of N, P, and K were increased with
higher doses of N, P, and K, respectively. The higher content
of N, P, and K nutrients may be attributed to the adequate
quantity and higher availability of these nutrients in the root
zone during plant growth period. Also, this increase was
generally caused by higher dry leaf yield obtained at the
same levels. These findings are in conformity with the results
reported by [5] where in higher nutrients content in stevia
plant was attributed to the higher availability of nutrients in
the root zone. [3] also recorded higher NPK content with
higher availability of NPK nutrients. Earlier [38] have also
reported that increased supply of nitrogen resulted in
increased plant N content by stevia. However, [18] in Japan
reported higher nitrogen (1.4%), phosphorus (0.3%) and
potassium (2.4%) content in stevia plant at harvest with
adequate fertilization. [32] reported that applied N, P and K
had little effect in altering the concentration of N, P and K in
stevia plant. The absolute control recorded the lowest N, P
and K concentrations. It has also been reported that P
deficiency reduced absolute root growth of rice (Oryza sativa
L.) [47].
Stevioside (STV) and total steviol glycosides (SG) contents in
stevia leaves were higher with treatment 100:100:240 kg ha
-1
NPK than all other treatments and control, which may be due to
combined effects of moderate levels of nitrogen and phosphorus,
and higher level of potassium. The greater STV content in leaf
with moderate dose of N may be attributed to the desired dose of
photosynthetic pigments. [21] reported that accumulation of
steviol glycosides in cells of stevia in vivo and in vitro was
related to the extent of the development of the membrane system
of chloroplasts and the content of photosynthetic pigments. [32]
reported that stevioside accumulation in leaf was significantly
improved by the moderate level of N. However, the maximum
content of rebaudioside A (Reb A) was recorded with the
application of 200:100:80 kg ha
-1
NPK. [3] showed that
combination of higher levels of nitrogen, phosphorus and,
potassium resulted in marginally higher contents of stevioside
and rebaudioside A in leaves at harvest as compared to
combination of lower levels of these nutrients. [45] from Brazil
reported that the deficiency of the major nutrients decreased the
stevioside content in the plant. Higher SG yield was obtained
with higher levels of nitrogen, phosphorus, and potassium
combination, this due to the combined influence of greater
nutrient concentrations and dry biomass yield under with those
this combination. Similar results were reported by [3] who
reported highest stevioside yield and rebaudioside A yield was
obtained with higher NPK levels and the lowest stevioside yield
and rebaudioside A yield was recorded with the crop applied
with no nutrients i.e., absolute control.
5. Conclusion
The results, obtained in the present study, suggest that the
stevia growth, yield, and quality are strongly controlled by
the exogenous supply of plant nutrition. Therefore, it can be
concluded that the application of 300:100:240 kg ha
-1
NPK is
helpful to increase the fresh biomass yield, fresh leaf yield,
dry leaf yield, and steviol glycoside yield as compared to
other combinations and absolute control. This superior
combination also resulted in the considerably higher content
American Journal of Biology and Life Sciences 2018; 6(3): 36-43 42
of nitrogen in stevia leaf. However, higher phosphorus and
potassium contents were obtained with 300:150:80 kg ha
-1
NPK and 100:50:240 kg ha
-1
NPK combinations,
respectively. The combination of 200:150:80 kg ha
-1
NPK
was found to be more effective for plant height and stem than
all other treatments while, the stevioside and total steviol
glycoside contents in stevia leaves were higher with
100:100:240 kg ha
-1
NPK combination. Thus, the
combination of 300:100:240 kg ha
-1
NPK could be
considered as an economically optimum level of nutrients for
stevia in sandy soil under north-western Moroccan
conditions.
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