1004
Journal of Applied Sciences Research, 9(1): 1004-1009, 2013
ISSN 1819-544X
This is a refereed journal and all articles are professionally screened and reviewed
ORIGINAL ARTICLES
Effect of Plant Density on Yield and Sugar Quality Characteristics of Sugar Beet
1
Hozayn, M., 1Tawfik, M.M., 2Abd El-Ghany, H.M. and 2Korayem A.M.
1
Field Crop Research, 2Plant Daises Departments, Agricultural and Biological Division, National Research
Centre. Dokki, Cairo, Egypt.
ABSTRACT
Optimum plant population density has been found to affect good yield and quality of extracted sugar in
most of the arable lands. A good plant stand gives complete occupation of the available space to achieve
complete light interception. Therefore, field trials were designed with the objective of determining the effect of
plant population densities on yield and quality of sugar beet plant. Two field experiments with three replications
were conducted in sugar beet production area at a private farm, Ferrmon Village, Dessok Province, Kafer ElSheikh Governorate during 2008/09 and 2009/10 successive winter seasons to study the effect of five plant
density (16, 24, 32, 36 and 40 thousands plants/fed*) on yield and quality of extracted sugar beet plants grown
on a clay soil. Growing sugar beet at 36000 plants/fed increased the yield of fresh roots and fresh foliage as well
as sugar yield as compared to the other plant densities, The same plant density recorded the highest values for
most of the studied quality characters .Increasing plant density from 16 to 36 thousands resulted in increases of
19.61, 8.11, 29.57 and 8.71% for sucrose, purity, sugar recovery and quality index % respectively. As for the
impurities planting density of 24000 plants/fed recorded the least values for K and Na, while 40000 planting
density/fed. recorded the least values for α- amino-N content. On conclusion, it is considered that the optimum
plant density to obtain economic yield with satisfied sugar extraction characteristics quality under the
circumstance of the experimental area in Kafer El-Sheikh Governorate is 36000 plant/fed .
Key words: Sugar beet, plant density, yield, quality, impurity.
Introduction
Sugar beet (Beta vulgaris L.) is considered to be the second source for sugar production in Egypt and in
many countries all over the world. The Egyptian government encourages sugar beet growers to increase the
cultivated area with sugar beet to increase sugar production and decrease the gap between sugar production and
consumption (34%) (Anonymous, 2003). Sugar beet intensification to the optimum density results in mature
plants that are sufficiently crowded to efficiently use resources such as water, nutrients, and sunlight, without
high mortality rate (Heitholt and Sassenrath, 2010).. Many factors influence the optimum plant population for a
crop: availability of water, nutrients and sunlight, length of growing season, potential plant size, and the plant’s
capacity to change its form in response to varying environmental conditions (morphological plasticity). Plant
density has been recognized as a major factor in determining the degree of competition between plants (Sadre,
2012). There is a need to use optimum plant density, which is expected to bring about a maximum yield of crop
when all the other inputs of production have been adequately met (Khaiti, 2012). Plant density per unit area of
cultivated land is a major factor in determining the quality and quantity of the sugar roots, for instance, optimum
plant density provides a larger area of nutrients which allows plant sufficient quantity of water, light and thus
raises the efficiency of photosynthesis which contribute to increase the dry matter proportion in the roots and
higher roots yield per unit area (Freckleton et al., 1999). Many researches have been conducted to determine the
optimum plant population densities for high root and sugar yield as well as the quality, Ramazan, (2002)
recommended that plant establishment should be 70 000-110 000 plants ha-1. Ismail and Allam (2007) reported
that sowing sugar beet at 70000 and 105000 per hectare gave high values of yield and quality traits. Masri
(2008), observed a positive effect of increasing plant density from 87500 to 100000 plants ha-1 as well as
significant increase in sucrose content, purity, extractable sucrose and sugar yield. Nassar (2001), found that
sucrose content and recoverable sugar percentages were linearly decreased with the reduction in plant density.
He added that root and sugar yield was maximized with plant density of 42000 plants fed-1. Awad (2000), found
that maximum sugar percentage was 20.33% for two rows machines planting on furrow land, 15 cm tillage
depth, 10 cm distance between ridges and 50 cm between rows. In this concern, El-Sarag (2009) studied three
plant densities (20, 28 and 46 thousand plants fed-1). There were insignificant effects of plant density on juice
Corresponding Author: Hozayn, M., Field Crop Research, Agricultural and Biological Division, National Research Centre.
Dokki, Cairo, Egypt.
E-mail: [email protected]
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J. Appl. Sci. Res., 9(1): 1004-1009, 2013
purity; the highest plant density (46 000 plants fed-1) recorded the maximum root fresh weight and sugar yield as
compared with the lower densities.
Lack of appropriate weather conditions for flowering sugar beet under Egyptian condition led to import its
seeds annually or at most every two years from aboard. So, application of the appropriate agronomic practices
especially for new imported cultivars is essential. The aim of the present investigation is to determine the
optimum plant population for high root yield and quality with lower detract agents of sugar beet in sugar beet
production area under Kafer El-Sheikh Governorate.
Materials and Methods
Two field experiments with three replications were conducted in sugar beet production area at a Private
Farm, Ferrmon Village, Dessok Province, Kafer El-Sheikh Governorate during 2008/09 and 2009/10 winter
seasons to study the effect of different planting densities (16 000, 24 000, 32 000, 36 000 and 40 000 plants/fed)
on yield and quality of sugar beet plants grown on a clay soil (clay 85%, silt 13.5% and sand 1.5%). The first
three and five plant density was tested in the first and second season respectively. The experimental unit
consisted of 7 ridges 50 cm apart and 8 meters a long (28 m2). The preceding summer crop was rice (Giza-177)
in both seasons. The soil was ploughed triple, settled, ridged and divided into plots. During soil preparation, the
recommended dose of phosphorus fertilizer was applied at a level of 200 kg calcium super phosphate fed-1
(15.5% P2O5). Two-three of sugar beet seed balls “cv. Oscarpoly” was sown in hills with the theoretical
numbers i.e., 3.81, 5.71, 7.62, 8.57 and 9.52 plants/m-2 on one side of ridge (50 cm apart) to establish the
planting population densities(16, 24, 32, 36 and 40 thousands plantsfed-1, respectively. Sowing dates were on
August 28th and September 6th in the first and second seasons, respectively. Plots were flooded irrigated
immediately after sowing. Plants were thinned twice and the later one was done to ensure one plant/hill.
Potassium in the form of potassium sulphate (48 % K2O) was added at the rate of 120 kg fed-1 in two equal
doses after thinning and 21 days later, respectively. Nitrogen fertilizer as ammonium sulphate (20.6 %N) was
added at the level of 100 kg N fed-1.was added in three equal doses after thinning (35 days from sowing), 21 and
42 days later, respectively. Other agricultural practices were kept the same as normally practiced in growing
sugar beet fields.
At harvest, plants in the four inner ridges of each plot were collected and cleaned, thereafter roots were
separated and weighted in kilograms and converted to estimate root yield (ton fed-1). Sugar yield (ton fed-1) was
calculated by multiplying root yield by root sucrose percentage. A sample of 10 kg of roots were taken at
random from each plot and sent to the Beet Laboratory at Hamool Sugar Factory to determine root and extracted
sugar quality. Alpha amino nitrogen (α-amino N), sodium (Na) and potassium (K) concentrations were
estimated according to the procedure of Sugar Company by Auto Analyzer described by Cooke and Scott
(1993). Sucrose (expressed as Pol %) was estimated in fresh samples of sugar beet root by using Saccharometer
according to the method described by A.O.A.C. (1995). Sugar loss was calculated using the following formula:
Sugar loss (%) = [(0.29) + (0.343 (K + Na)) + (0.094 α-amino N)]. Sugar recovery (%) was calculated using the
following equation: Sugar recovery (%) = sucrose (%) - sugar loss (%) (Cooke and Scott (1993). Recoverable
sugar yield (ton fed-1) was calculated using the following equation of Mohamed (2002): Recoverable sugar yield
= root yield (ton ha-1) x sugar recovery (%). Quality index was calculated as (sugar recovery (%) x 100)/sucrose
(%). Gross sugar yield (ton fed-1) = root yield (ton fed-1) x sucrose %. Sugar loss yield was computed as: root
yield (ton fed-1) x sugar loss (%).
The analysis of variance of Randomized Complete Block Design (RCBD) experiment was carried out using
MSTAT-C Computer Software (MSTAT, 1988). Means of the different treatments were compared using the
least significant difference (LSD) test at P<0.05.
Results and Discussion
I. Root parameters:
It is worthy from the statistical description in tables1-5 to note that the values of CV% indicate that the data
presented is dependable and highly confident to conclude the results.
Data presented in Table (1) showed that plant density significantly affected all the studied root characters.
Sur beet root diameter, length and weight seemed to be greater under the lowest planting density (16000
plant/fed-1).. These findings are in harmony with those obtained by Sadre (2012), who mentioned that, the
increase in root characters value can be explained through the fact that, the higher biomass in treatments having
comparatively less plant population was possibly due to optimum utilization of soil and other environmental
resources with lower competition by the crop. Several studies have shown that biomass yield decreases
progressively as the number of plants increases in a given area because the production of the individual plant is
reduced (Ahmad et al., 2010). In this concern, Heitholt and Sassenrath (2010) stated that plant populations
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J. Appl. Sci. Res., 9(1): 1004-1009, 2013
affect most root parameters of sugar beet even under optimal growth conditions and therefore it is considered a
major factor determining the degree of competition between plants.
Table 1: Effect of plant density on root parameters of sugar beet plant grown in clay soil (average of 2008/09 and 2009/10 seasons).
Character
Root parameter
Merge cell
Plant density
Length
Diameter
Weight
-1
(1000 plants fed )
(cm)
(cm)
(kg)
16
25.38 c
25.10 a
2.40 a
24
31.32 b
22.33 b
1.66 b
32
36.08 a
20.00 b
1.23 c
36
37.15 a
14.00 c
1.20 c
40
38.00 a
10.10 d
0.95 d
F- sig.
**
**
**
LSD at 5%
2.87
2.75
0.21
CV
4.54
7.97
7.46
Values for each mean within a column, followed by a different letter are significantly different at the 0.05 level of probability according to
Least Significant Difference (LSD) test. **, statistically significant difference at P = 0.01, CV= Coefficient of Variation.
II. Yield (ton fed -1):
Yield (ton. Fed-1)
Data illustrated in Fig. 1 show that increasing plant density from 16 to 36 thousands plants fed-1 positively
affected yield of sugar beet, El-Sarag (2009) came to the same conclusion. Further increase to 40 thousands
negatively affected the yield characters. Similar results were obtained by Abd El- Kader (2005) who found that
plant density of 56000 plant fed-1 produced the highest root and sugar yield compared to the low density 33600
plant.fed-1. Leilah et al., (2005) stated that, plant population markedly affected all studied characters in the two
seasons. The highest root and sugar yield ha-1 were obtained with sowing sugar beet on both sides of ridges, 70
cm width and 25 cm between plants (114240 plants ha-1). In this concern, (Hamidia et al., 2010), stated that,
biomass yield decreases progressively as the number of plants increases in a given area because the production
of the individual plant is reduced. Moreover, Khaiti (2012) mentioned that, use of high population increases
interplant competition for light, water and nutrients, which may be detrimental to final yield.
44
42
40
38
36
34
32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
a
16 000 plants
36 000 plants
c
b
24 000 plants
40 000 plants
32 000 plants
d
e
c
b a a
d
e
Fresh root
Fresh foliage
d
b a c
Gross sugar
e c
a a b
Recoverable
sugar
c c a a b
Loss sugar
Yield (ton fed.-1)
Fig. 1: Effect of plant density on yield of sugar beet plant grown in clay soil (average of 2008/09 and 2009/10
seasons). LSD = 2.15, 0.43, 0.54, 0.50 and 0.12 for fresh root and foliage, gross, recoverable and loss
sugar yield respectively. Means with different letters above bars were significantly different at the 0.05
level according to Least Significant Difference (LSD) test.
III. Quality parameters:
Significant differences were obtained for the impact of plant densities on quality parameters of sugar beet
plant (Table 2). The highest sucrose, purity, sugar recovery and quality index were recorded in 36 000 plant
density treatment. In other words all the previous characters positively affected by increasing plant density from
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J. Appl. Sci. Res., 9(1): 1004-1009, 2013
16 to 36 thousands causing an increase of 19.61, 8.11, 29.57 and 8.71% for sucrose, purity, sugar recovery and
quality index % respectively. On the other hand the highest value of sugar loss to molasses amounted to 4.66%
under 16 000 plant population density. This result is consistent with previous research of (Ismail and Allam
2007). In this concern, Masri (2008), observed a positive effect of increasing plant density from 87500 to
100000 plants ha-1 and significantly increased sucrose content, purity, extractable sucrose and sugar yield.
Moreover, Cakmakci et al., (1998) stated that, when plant density reached above optimum levels, recoverable
sugar yield declined due to reduction in root yield even though sugar content increased. They added that, wider
plant spacing always resulted in lower sugar content. Khaiti (2012) mentioned that, as plant population
decreased and gap rate increased, poor quality plants developed and non-sugar content increased leading to
Extractable Sugar Content and hence recoverable sugar yield. These results might be due to the better nutrient
utilization and maximum light interception which resulted in better leaf growth (Baiyan and Jingping, 2004).
Table 2: Effect of plant density on some quality parameters of sugar beet plant grown in clay soil (average of 2008/09 and 2009/10
seasons).
Character
Quality parameters (%)
Plant density
Sucrose
Purity
Sugar
Recovery sugar
Quality
(1000 plants fed-1)
loss
Index
16
16.70 d
69.93 b
5.02 a
11.66 d
69.94 c
24
17.48 c
74.40 a
4.45 c
13.03 c
74.55 b
32
19.20 ab
71.40 b
4.77 b
14.43 b
75.11 b
36
19.90 a
75.60 a
4.53 c
15.37 a
77.23 ab
40
18.50 b
74.50 a
4.43 c
14.07 b
76.04 ab
F- sig.
**
**
**
**
**
LSD at 5%
0.75
2.73
0.22
0.89
1.92
CV
2.16
1.98
2.52
3.45
1.37
Values for each mean within a column, followed by a different letter are significantly different at the 0.05 level of probability according to
Least Significant Difference (LSD) test. **, statistically significant difference at P = 0.01, CV= Coefficient of Variation.
IV. Impurity components:
The technical beet quality, i.e. the process ability in the sugar factory, however, is determined not only by
sucrose concentration, but also by the concentrations of other constituents that impair white sugar recovery.
These are called root impurities such as potassium, sodium, amino acids and other nitrogenous compounds as
well as K+Na, K+Na/ α- amino-N, K/Na ratio and impurities index.
Table (3) shows that, all plant density treatments significantly affected all the previous characters with
superiority of 16000 plant density treatment which recorded the highest values of K, α- amino-N, K+Na, K/Na
ratio and impurities index. On the other hand 32000 recorded the highest values for Na and K+Na/α- amino-N
(alkalinity coefficient). Similar results were obtained by Ahmed et al., (2010). In this concern, Carter (1986)
stated that α amino nitrogen (Neutral amino acid, glutamine, asparagines, pyrrolidone carbonic acid, amio-butric
acid) is consider one of the main impurities and undesirable character which decrease the quality as their
concentration in juice increases. They interfere with the crystallization process, which causes a greater
proportion of the sugars to be recovered as molasses with a reduction in refined sugar. They added that, both K
and Na are impurities and their ratio interferes with the crystallization process, which causes a greater
proportion of the sugars to be recovered as molasses with a reduction in refined sugar. Moreover, Malbaša et
al., (2008) found that these nitrogenous compounds affect the industrial purification of sucrose and contributes
to the actual sugar so they affect the quality of sugar beet. Moreover, Furthermore, Van der poel et al., (1998)
said that, the molassigenic substances such as potassium, sodium, raffinose and N compounds such as amino-N
and betaine increase the molasses loss, whereas invert sugar and glutamine lead to color formation during
evaporation and crystallization as a consequence of the Maillard reaction. This is regarded as a major quality
impairing factor for white sugar.
Table 3: Effect of plant density on impurity components of sugar beet plant grown in clay soil average of 2008/09 and 2009/10 seasons).
Character
Impurity components (mmol 100 g-1 beet paste)
Plant density
K
Na
α- amino-N
K+Na
K/Na
Alkalinity
Impurity
(1000 plants fed-1)
ratio
coefficient
index
16
6.57 a
5.31 a
6.95 a
11.88 a
1.24 a
1.71 d
6.26 a
24
5.66 b
5.17 a
4.70 b
10.83 b
1.09 d
2.30 c
4.53 b
32
6.42 a
5.36 a
4.64 b
11.78 a
1.20 b
2.54 a
4.24 bc
36
5.88 b
5.24 a
4.56 b
11.12 b
1.12 c
2.44 ab
3.95 c
40
5.66 b
5.18 a
4.53 b
10.84 b
1.09 d
2.39 bc
4.19 c
F- sig.
***
ns
***
**
***
***
***
LSD at 5%
0.36
ns
0.22
0.61
0.02
0.11
0.31
CV
3.19
2.51
2.32
2.82
1.15
2.48
3.51
Values for each mean within a column, followed by a different letter are significantly different at the 0.05 level of probability according to
Least Significant Difference (LSD) test. ns= no significant, **, statistically significant difference at P = 0.01, CV= Coefficient of Variation.
1008
J. Appl. Sci. Res., 9(1): 1004-1009, 2013
Conclusion:
Plant population density is one of the main agronomic practices for maximizing economic returns by
affecting yield and quality of sugar beet plant. High plant density can significantly increase yield per unit area.
The advantages of high population density include: the potential to increase yields significantly, synchronize the
crop cycle and optimize land use. It could be concluded from this study that sugar beet intensification could be
achieved under the circumstance of Kafer El-Sheikh Governorate by growing it with the planting density of
36000 plant/fed produced the highest root yield and sugar yield with good quality and less detract components.
Acknowledgment
This work was funded by The National Research Centre through the project entitled: “The development of
integrated management to improve productivity (quantity and quality) of sugar beet”. Project No. 8040716
during in-house projects strategy 2007-2010. The principal investigator, Prof. Dr. Ahmed Mohamed Korayem.
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