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Heliyon 9 (2023) e17262
Available online 14 June 2023
2405-8440/© 2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/).
Grain yield and quality responses of durum wheat (Triticum
turgium L. var. durum) to nitrogen and phosphorus rate in Yilmana
Densa, Northwestern Ethiopia
Alemayehu Assefa, Bitwoded Derebe
*
, Nigatu Gebrie, Agegnehu Shibabaw,
Wudu Getahun, Oumer Beshir, Abebe Worku
Amhara Agricultural Research Institute, P.O.Box. 08, Bahir Dar, Ethiopia
ARTICLE INFO
Keywords:
Amhara region
Crop parametres
Economic analysis
Protein content
ABSTRACT
Proper rate of fertilizer application is the major factor that affects yield and quality of durum
wheat. Location specic fertilizer recommendation is lacking for durum wheat, therefore, ni-
trogen (N) and phosphorus (P) eld experiment on durum wheat was carried out on farmer’s eld
in 2017 and 2018 cropping seasons at Yilmana Densa district, Northwestern Ethiopia. The
objective was to examine the response of durum wheat to N and P application and determine the
optimal rate of nitrogen (N) and phosphorus (P) for durum wheat production in the district and
similar agro ecology areas. Factorial combinations of four N levels (0, 90, 180 and 270 kg ha
−1
)
and four P levels (0, 17.5, 35 and 52.5 kg ha
−1
) were evaluated in a randomized complete block
design with three replications per site, over two sites in each year. Results indicated that N
signicantly affected most of the crop parametrs including grain yield, plant height, total number
of tillers and effective tillers, spike length and seeds per spike, and the maximum value of the
parameters recorded at the highest rate of N while application of phosphorus affected grain yield,
plant height and spile length. The interaction effect of N and P signicantly affected grain yield,
plant height and seeds per spike. Grain yield showed quadratic and linear response to N and P
application, respectively. The maximum grain yield (5182 kg ha
−1
) was obtained from the highest
rate 270/52.5 N/P kg ha
−1
. The economic analysis revealed application of 270/52.5 N/P kg ha
−1
gave the highest net benet of 169741 ETB ha
−1
with marginal rate of return 1453% and full lls
the standard for quality of durum wheat production and hence can be recommended in Yilmana
Densa District and other similar agro-ecologies in Ethiopia. The study revealed the need to further
investigation for optimal N and P rates for different durum wheat varieties as they differ in
protein content under the same management practices.
1. Introduction
Durum wheat (Triticum turgium L. var. durum) is the second most important cultivated wheat species in the world next to bread
wheat [1]. Ethiopia is the center of diversity for durum wheat [2] also the leading producer in sub-Saharan Africa countries. In
Ethiopia, durum wheat is traditionally grown on heavy black clay (Vertisols) on the residual moisture and recently being grown on
* Corresponding author.
E-mail address: bitwoded12@gmail.com (B. Derebe).
Contents lists available at ScienceDirect
Heliyon
journal homepage: www.cell.com/heliyon
https://doi.org/10.1016/j.heliyon.2023.e17262
Received 28 November 2022; Received in revised form 2 June 2023; Accepted 12 June 2023
Heliyon 9 (2023) e17262
2
light soils under rainfed conditions. Although the primary use of durum is in the manufacture of pasta products (macaroni, spaghetti,
and noodles), it is also used in making fermented leveled bread, called injera and other indigenous food preparations in Ethiopia [3].
According to Ref. [4], bread and durum wheat were produced in Ethiopia by approximately 4.94 million households during the
“meher” and “belg” (rain and dry) seasons on an estimated 2.13 million ha of land, with an annual production of 6.23 million tons and
a mean national yield of 3.05 t ha
−1
. Regardless of the long history of durum wheat cultivation and its importance in Ethiopian
agriculture, little emphasis was given on improving the quality and grain yield of durum wheat in the past and its average productivity
remains far below the world average (3.5 t ha
−1
) and very low in Amhara region as compared to the national average (3.046 t ha
−1
) [4,
5].
Low soil fertility due to continuous nutrient uptake of crops, mono-cropping system and slow progress in developing wheat cul-
tivars with durable resistance to disease are considered the most important constraints limiting wheat production in Ethiopia [6]. The
soils of Ethiopian highlands are mainly decient in organic matter, nitrogen and phosphorus. These deciencies are due to nutrient
mining by cereal mono-cropping and leaching losses which resulted reduction in yield and quality of crops [7]. Mineral fertilizers or
combined organic and inorganic fertilizers have been found to have a signicant benecial effect on food production worldwide, and
are an indispensable component of many agricultural systems [8]. The low productivity also allied with low fertilizer use (nitrogen and
phosphorus) and insufcient organic matter application [9]. Currently, there is a high demand to both commercial and small-scale
farmers for durum wheat with high grain yield and better end-use quality. The yield and end-use quality of durum wheat depend
upon the protein and gluten content which is largely inuenced by the genotype and environment especially the nitrogen element
available in the soil [10]. On the other hand most of the quality parameters of durum wheat increased as nitrogen application increased
beyond 120 kg N ha
−1
[9]. Phosphorus (P) is the second most important element for crop production, it is known to be involved in
many physiological and biological processes of plants [7].
Consequently, low volumes and poor quality of the national durum wheat production in Ethiopia leads the pasta industries to
import the required raw material from abroad [3]. These pasta producers used to rely on massive importation of durum wheat grains,
which was not a sustainable long-term business strategy due to high and volatile costs. Pasta import increased two-fold between 2011
and 2015, when it reached 50,000 t at a cost of about
€
40 million [11]. The food crises all over the world and increasing population
pressure demand urgent need to increase the quantity and improve the quality of grains. To reverse this trend, the Ethiopian Millers
Association has eagerly explored the possibility to procure the needed raw material directly from local farmers to reduce production
costs and increase competitiveness against foreign pasta imports. Increasing domestic quality produce could mitigate not only the
shortage but also substitutes the import of huge industrial raw materials. The national research institutes and pasta processing in-
dustries also jointly working to improving durum wheat grain quality. There is also a plan to establish pasta and macaroni industries by
public developmental agencies and unions in various parts of the Amhara region. However, the is limited information on the effect of
NP fertilizer rate on the production and quality of durum wheat, as a result, farmer’s even researchers use the bread wheat NP rate
recommendation for durum wheat which may have effect on the productivity and quality of durum wheat. Therefore, the objective of
Fig. 1. Map of the study area.
A. Assefa et al.
Heliyon 9 (2023) e17262
3
the experiment was to examine the response of durum wheat to N and P application and determine the optimal rate of nitrogen (N) and
phosphorus (P) for durum wheat production in Nitosols of Yilmana Densa district and similar agro ecology areas of northwestern
Ethiopia.
2. Material and methods
2.1. Description of the study area
The experiment was conducted in Yilmana Densa district on farmer’s eld during the 2017 and 2018 main cropping season (two
elds in each year). Yilman Densa district is located on latitude of 11◦5
′
to 11◦25
′
N and longitude of 37◦20
′
to 37◦40
′
E at about 42 km
far from Bahir Dar with an altitude ranging from 2216 to 2696 m.a.s.l. (Fig. 1). The rainfall pattern of the study area is unimodal, about
79% (1127 mm) of the rainfall received from June to October. During these months the mean minimium and maximium temperature
ranged from 8 to 12 ◦C and 23 to 26 ◦C, respectively (Fig. 2). Most of the farmers in the study area used cereal based rotation and
experimental sites with maize precursor were selected for the study. The soil of the experimental sites was Nitosol and analysis on some
of the selected soil physicochemical properties for composite surface soil (0–20 cm depth) samples collected at planting showed pH
4.96, organic carbon 1.6%, total nitrogen 0.16%, available phosphorus 8.49 ppm and cation exchange capacity 28.55 mol (+)/kg soil
(NHAc). The soil sample analysis result further revealed the acidic nature of the soil, and available P content was in optimum range
according to Ref. [12]. While organic carbon and total N rated low [13]. The overall result of soil analysis showed the need to design for
reduce soil acidity, improve organic carbon and total nitrogen through integrated soil fertility management approach.
2.1.1. Treatments, experimental design and procedures
A factorial combination of four N rates (0, 90, 180 and 270 kg ha
−1
) and four P rates (0, 17.5, 35 and 52.5 kg ha
−1
) was evaluated in
RCBD with three replications in a gross plot size of 4 m in length and 3.2 m in width while the net plot size was 4 m ×2.8 m. All the
phosphorous and 1/3 of nitrogen was applied at planting while the remaining 2/3 N was applied during mid-tillering stage of durum
wheat. The experimental eld was prepared accourding to the local practice. Thus, the land was ploughed four times using oxen before
planting to pulverize the soil and make control of early emerging weeds. Seeds of durum wheat variety ‘Mangudo’ was uniformily hand
drilled at seed rate of 150 kg ha
−1
with 20 cm rows spaced and covered by soil on 28th of June to 2nd of July in 2017 and on 3rd of July
to 6th of July in 2018. The space between blocks and plots were 1.5 m and 0.6 m, respectively. One hoeing at early tillering stage and
hand weeding was carried out to keep the plots free from weeds and to provide better aeration. The next two hand weeding activities
were operated at mid-tillering and booting stage of durum wheat.
2.1.2. Data collection and analyses
Data were collected from a total of four experimental sites (two sites in each year) and averaged value of each parameter for the
year was considered for analysis. Data on plant height, spike length, number of tillers, effective tillers, seed per spike, thousand kernel
weight and dry grain protein content were collected from the net plot using random sampling. Ten randomly selected plants and ten
spiks were used to measure plant height and spike length, respectively. Plant height was measured from the bottom of the plant to the
tip of spike. Total number of tillers were counted within one metersquare quadrant and those tillers with spikes were considered as
effective tillers. Grain yield (Gy) was collected from the whole net plot for the purpose of more accuracy and precision. About 250 g
grain samples was taken to measure grain protein content using Infratec 1241 Grain Analyser (Foss, Hilleroed) at Amhara Agricultural
Research Institute grain quality laboratory. The Infratec 1241 is a whole grain analyser using near-infared transmittance technology to
test multiple parameters (moisture, protein, oil, starch etc) in a broad range of grain and oilseed commodities.
The data were subjected to analysis of variance (ANOVA) using SAS (statistical analysis System) GLM procedures version 9.0.
Combined analysis over years was made considering year as a random variable. The response of wheat to nitrogen and phosphorus
rates either for its linearity or quadratic was detected using single degree of freedom orthogonal contrast test. For the quadratic re-
sponses, prediction of the optimal level of fertilizer for maximum yield was done using polynomial response equation [14]. Duncan
Fig. 2. Monthly average rainfall and monthly mean maximum and minimum temperature during 2017 and 2018 growing seasons in the study area.
A. Assefa et al.
Heliyon 9 (2023) e17262
4
multiple range test at 5% of probability levels was used for mean separation when the analysis of variance indicates the presence of
signicant differences [15]. Correlation analysis also made between grain yield and protein content.
2.1.3. Partial budget analysis
Partial budget analysis was made based on CIMMYT methodology [16]. Besides to the current cost price ratio (CPR), economic
return of durum wheat grain yield was performed at the scenario when fertilizer cost increased by double (100%) compared to the
current cost while durum wheat grain price remain unchanged. The market prices of durum wheat grain (35.08 ETB kg
−1
) of the month
January and February 2020 was considered for the economic analysis. Similarly, cost of N, ETB 33.33 kg
−1
(derived from cost of urea,
ETB 15.33 kg
−1
) and cost of P, ETB 59.75 kg
−1
(derived from cost of NPS, ETB 16.25 kg
−1
) of the year 2020 were used. Fertilizer NPS
(19% N, 16.6% P, 7% S) is commonly available in the market and farmers usually used it as source of phosphorus whereas TSP is not
easily available and used only for the experiment purpose. The CPRs were calculated and these resulted 0.95 and 1.90 for N cost kg
−1
to
durum wheat grain price kg
−1
; and 1.70 and 3.40 for P cost kg
−1
to durum wheat grain price kg
−1
for the current situation and
sensitivity analysis, respectively.
Total cost that varied (fertilizer cost) for each treatment were calculated and treatments were ranked by sorting their total variable
cost (TVC) in ascending order and dominance analysis was used to eliminate those treatments costing more but producing a lower net
return than the next lowest cost treatment. Net returns were calculated by deducting the variable costs of N and P from the gross return.
A treatment that is non-dominated and having the highest net return with minimium acceptable marginal rate of return (MRR) value of
100% is said to be economically protable [16]. Marginal rate of return was calculated by a change in net return over a change in total
variable cost.
3. Results and discussion
3.1. Yield components
Yield components such as plant height, seed per spike, spike length, number of total tillers and effective tillers were analyzed
combined over years. Plant height and seeds per spike were signicantly affected by main effect of both N and P and their interaction
whereas spike length, grain protein content, total and effective tillers were signicantly affected by main effect of nitrogen (Table 1).
Plant height, total and effective tillers, spike length and seeds per spike increased as N rates increased (Table 2). As the N rate increased
from nil to 270 kg ha
−1
it had an increament of 41% in plant height and spike length, 89% total tiller, 101% effective tillers and 92%
number of seed per spike over the respective control. Increasing in plant height in reponse to N rate was in agreement with the ndings
[17] similarly, increasing N rate increased plant height [7]. Spike length increase in response to N and similar result also reported by
Ref. [18]. Increasing on number of tillers in response to N rate was also reported by Refs. [7,17]. Increasing in the number of effec-
tive/fertile tillers with the increase in nitrogen levels could be attributed to the well-accepted role of nitrogen in accelerating the
vegetative growth of plants [18]. An increased application of nitrogen increases the number of kernel per spike [19]. The optimal N
and P interaction for the highest plant height and seeds per spike were 270/52.5 N/P kg ha
−1
and 270/17.5 N/P kg ha
−1
respectively
(Table 3). The result indicated that high demand of nutrient especially nitrogen at vegetative and booting stage of the crop to boost the
grain yield related components of durum wheat.
3.2. Grain quality parameters
Grain quality was expressed in terms of thousand kernel weight and grain protein content. Thousand kernel weight ranged from
34.8 to 38.3 g (Table 2). As Nitrogen rate increased the TKW increased up to 184 kg ha
−1
, further increased N decreased TKW. In line
with the present result thousand kernels weight ranges of 42.5–49.5 g for durum wheat varieties [20]. The standard thousand-kernel
weight for pasta industry is in the range of 35–40 g according to Ref. [21]. Protein content ranged from 7.5 to 11.5%, the highest
protein content obtained from high rate of N as protein content is directly inuenced by nitrogen rate (Table 2). As the nitrogen rate
increased from nil to 270 kg ha
−1
the protein content increased by 53%. In agreement with these result the highest grain protein
Table 1
Signicance value (P value) on grain yield and yield related parametrs of durum wheat at Yilmana Densa district, Northwestern Ethiopia (combined
over 2017 and 2018 crop season).
source of variation df GY TKW Pht TT ET SPS SL
Year (yr) 1 ns *** *** * * ** ***
yr*rep 4 ns ns ns ** ** ns ns
N 3 *** ns ** ** ** ** *
yr*N 3 ns * *** ** ** ns ***
P 3 ** ns ** ns ns * ns
yr*P 3 ns ns ns ns ns ns ns
N*P 9 * ns * ns ns ** ns
yr*N*P 9 ns ns ns ns ns ns ns
*, ** and *** signicant difference at 5, 1 and 0.1% level of signicance, respectively; ns non-signicant difference. GY-grain yield, TKW-thousand
kernel weight, Pht-plant height, TT-number of total tillers, ET-number of effective tillers, SPS-number of seed per spike, SL-spike length.
A. Assefa et al.
Heliyon 9 (2023) e17262
5
(13.09%) was accumulated at the highest N rate (120 kg N ha-1) [19]. But in contrast to this nding, additional nitrogen fertilization
did not signicantly increased grain protein content of the durum wheat at Debre Zeit Agricultural Research Center, Ethiopia [9]. The
quality of durum wheat is highly dependent on the protein content of the grain, which is largely dependent on genotypes and
inuenced by environment, especially nitrogen (N) availability of the soil [9]. The acceptable Ethiopian standard protein content for
whole durum wheat semolina is 11.5% [22]. The protein content of wheat grains may vary between 10% and 18% of the total dry
matter [23].
3.3. Grain yield
The combined analysis over years on grain yield showed non-signicant difference of year interaction with N, with P and with N*P
indicating that wheat yield response for the treatment is similar trend across the years (Table 1). Grain yield signicantly responded to
the main and interaction effects of N and P. The response for N was quadratic while P was linear (Fig. 3a and b). The equation for
predicting agronomic optimum N rate for highest grain yield (Gy) was generated from the quadratic response function (Eq-1).
Accordingly, the highest grain yield (4492 kg ha
−1
) was obtained on the application of 280 kg N ha
−1
. While the phosphorus rate for
highest grain yield couldn’t be determined as the response was linear (Eq-3). The linear grain yield response to P application might be
due to soil acidity (pH 4.96, as indicated in the description of the study area) which make the applied phosphorus not fully available to
the crop and indicate the need to increase phosphorus level more.
Gy = − 0.04718N2+26.39031N+801.9698,R2=0.99 (1)
26.39031 −0.09436N=0(2)
derived from Eq-1.
Gy =2622.47223 +15.41596P,R2=0.9283 (3)
The rate for N*P interaction was determined from multiple regression equation:
Gy =686.36731 +24.24907N+4.4039P−0.04718N2+0.08157NP (4)
The highest grain yield (5182 kg ha
−1
) obtained from the application of 270/52.5 kg N/P ha
−1
while the lowest yield obtained at
the lowest NP rate (Fig. 3c). Application of 270/52.5 kg N/P ha
−1
gave a yield advantage of 4496 kg ha
−1
(655%) over unfertilized
plot. Yields increased with increased NP fertilizer rates. This result in line with the nding of [7,19]. The correlation analysis between
grain yield and protein content indicated positive and signicant (P <0.001) correlation with correlation coefcient, r =0.76. This
implies that high management levels towards increasing a grain yield improves the protein content and then grain quality. The highest
grain yield of any crop is the result of positive relationships of most yield components due to nitrogen fertilizer application [17,19].
Table 2
Main effect of N rate on some yield components and grain quality parameters of durum wheat at Yilmana Densa (combined over seasons 2017 and
2018, PC only for 2017).
N rate (kg/ha) Plant height
(cm)
Spike length
(cm)
No. of total tiller (m
−2
) No. of Effective tiller (m
−2
) No. of seeds spike
−1
TKW (g) PC (%)
0 56.8
c
3.2
d
34.9
d
31.8
c
19.7
c
34.8
a
7.5
c
90 76.1
b
4.1
c
50.9
c
49.5
b
29.8
b
37.0
a
7.9
c
180 79.7
a
4.3
b
62.4
b
60.8
a
35.8
a
38.3
a
9.9
b
270 80.2
a
4.5
a
65.8
a
63.9
a
37.9
a
36.1
a
11.5
a
CV (%) 2.8 5.3 9.6 10.3 11.6 7.0 4.3
Numbers with different letter within the column are signicantly different at 5% level of signicance using Duncan multiple range test. TKW-
thousand kernel weight, PC-protein content.
Table 3
The interaction effect of NP fertilizer on plant height and no. of seeds per spike of durum wheat at Yilmana Densa (combined over 2017 and 2018).
N rate (kg/ha) Plant height (cm) Number of seed per spike
P rate (kg ha
−1
) P rate (kg ha
−1
)
0 17.5 35 52.5 0 17.5 35 52.5
0 56.8
f
56.05
f
56.66
f
57.65
f
21.83
e
19.17
e
19.31
e
19.58
e
90 72.53
e
75.98
d
76.81
cd
79.03
bc
23.46
e
34.40
bc
29.44
d
32.04
cd
180 75.69
d
79.63
b
80.76
ab
82.92
a
33.78
bcd
36.07
abc
38.10
ab
35.65
abc
270 75.76
d
80.29
b
81.53
ab
83.06
a
35.20
abc
39.66
a
39.20
a
37.87
ab
Numbers with the different letter for each of the parameter are signicantly different at 5% level of signicance using Duncan multiple range test.
A. Assefa et al.
Heliyon 9 (2023) e17262
6
3
Fig. 3. Grain yield response of durum wheat to applied nitrogen (a) and phosphorus rate (b) and NP interaction (c) in Yilmana Densa district,
Northwestern Ethiopia (combined over 2017 and 2018).
Table 4
Partial budget analysis of N and P fertilizer application on durum wheat production in Yilmana Densa district (combined data of 2017 and 2018
cropping season) under two scenarios
Treatments Grain yield (kg
ha
−1
)
Gross benet (ETB
ha
−1
)
Current situation Sensitivity analysis
N rate (kg
ha
−1
)
P rate (kg
ha
−1
)
TVC (ETB
ha
−1
)
NB (ETB
ha
−1
)
MRR
(%)
TVC (ETB
ha
−1
)
NB (ETB
ha
−1
)
MRR
(%)
0 0 686 24091 0 24091 0 24091
0 17.5 763 26797 1046 25751 159 2091 24705 29
0 35 841 29502 2091 27411 159 4182 25319 29
90 0 2487 87281 2999 84281 6262 5999 81282 3081
0 52.5 918 32207 3137 29070 D 6273 25933 D
90 17.5 2692 94495 4045 90450 590 8090 86405 245
90 35 2898 101710 5091 96619 590 10181 91529 245
180 0 3523 123642 5999 117643 2315 11997 111645 1107
90 52.5 3103 108924 6136 102788 D 12272 96652 D
180 17.5 3857 135366 7044 128322 1021 14089 121277 461
180 35 4191 147090 8090 139000 1021 16180 130910 461
270 0 3794 133176 8998 124178 D 17996 115180 D
180 52.5 4525 158814 9135 149678 1021 18271 140543 461
270 17.5 4257 149409 10044 139366 D 20087 129322 D
270 35 4719 165643 11089 154554 250 22178 143464 75
270 52.5 5182 181876 12135 169741 1453 24270 157606 676
TVC-total variable cost, NB-net benet, MRR-marginal rate of return, ETB-Ethiopian Birr, D-dominated treatment.
A. Assefa et al.
Heliyon 9 (2023) e17262
7
3.4. Economic benet
The partial budget analysis indicated most of the treatments gave highest net benets with marginal rate of return greater than
100% (Table 4). Fertilizer application of 270 kg N with 52.5 kg P ha
−1
gave highest net benet of 169741 Ethiopian Birr (ETB) ha
−1
with marginal rate of return (MRR) 1453% followed by fertilizer rate of 270 kg N with 35 kg P ha
−1
which gave net benet of 154554
ETB ha
−1
with marginal rate of return 250%. Sensitivity analysis (when the fertilizer cost increased by double while grain price remain
unchanged) revealed the rst option of the recommendation (270 kg N with 52.5 kg P ha
−1
) remain stable with net benet of 157606
ETB ha
−1
and MRR 676%. This recommendations can full lls the standard for quality of durum wheat (36.1 g thousand kernel weight
and 11.5% protein content).
4. Conclusion and recommendations
Nitrogen and phosphorus fertilizer showed quadratic and linear response to grain yield, respectively. Application of 270/52.5 kg
N/P ha
−1
gave a yield advantage of 655% over unfertilized and can be recommended as the rst option where as depending on
fertilizer cost variability fertilizer application of 270/35 N/P kg ha
−1
or 180/52.5 N/P kg ha
−1
can be considered as alternative option
for poor farmers who are in constraint of cash. The linear response of grain yield to phosphorus fertilizer application indicated that
optimal agronomic rate couldn’t be achieved and implies further investigation in the study area. Moreover, as durum wheat varieties
differ in protein content under the same management practices, selection of those varieties with high protein content help a grower to
reduce N inputs to achieve high protein content at lower N level should be a research area.
Author contribution statement
Bitwoded Derebe Agegn: Conceived and designed the experiments; Performed the experiments; Analyzed and interpreted the data;
Contributed reagents, materials, analysis tools or data; Wrote the paper. Alemayehu Assefa: Conceived and designed the experiments;
Performed the experiments; Analyzed and interpreted the data; Wrote the paper. Nigatu Gebrie: Agegnehu Shibabaw: Wudu Getahun:
Oumer Beshir: Abebe Worku: Performed the experiments; Contributed reagents, materials, analysis tools or data.
Data availability statement
Data will be made available on request.
Additional information
No additional information is available for this paper.
Declaration of competing interest
The author declared that there is no conict of interest.
Acknowledgement
The authors acknowledge Adet Agricultural Research Center and Amhara Agricultural Research Institute for their full budget
support and facilitation during implementation of the work.
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