Directory UMM :Data Elmu:jurnal:S:Scientia Horticulturae:Vol83.Issue2.Febr2000:
Scientia Horticulturae 83 (2000) 127±137
The effects of fertilizer rate on vegetative growth, yield
and fruit quality, with special respect to pigments, in
black chokeberry (Aronia melanocarpa) cv. `Viking'
Niklas Jeppsson*
BalsgaÊrd-Department of Horticultural Plant Breeding, Swedish University of Agricultural Sciences,
FjaÈlkestadsvaÈgen 123-1, S-291 94 Kristianstad, Sweden
Accepted 6 May 1999
Abstract
The effect of fertilizer rate on fruit quality parameters in the black chokeberry (Aronia
melanocarpa [Michx] Ell.) cv. `Viking' was studied over three years. A combined N±P±K fertilizer
was applied in different rates. Plant height, yield, berry weight, anthocyanin content, content of
brown compounds, content of soluble solids, anthocyanin composition and total acidity were
recorded for the different treatments. Increased application of fertilizers resulted in increased
vegetative growth and yield whereas the content of anthocyanins and total acidity decreased. Mean
berry weight, content of brown compounds, soluble solids and anthocyanin composition were
unaffected. Correlations between the different parameters were calculated at single plant level.
Positive correlations were found between plant height and yield, between plant height and browning
index, and between anthocyanin content and total acidity. Negative correlations were found
between plant height on one hand, and anthocyanin content and total acidity on the other hand. It
was concluded that an increased fertilizer application results in increased growth and higher yield
whereas pigment content and total acidity decrease. Maximum production of anthocyanins per plant
was obtained with a medium high fertilizer rate (50 kg N/ha, 44 kg P/ha, 100 kg K/ha). # 2000
Elsevier Science B.V. All rights reserved.
Keywords: Rosaceae; Aronia; Fertilizer; Yield; Fruit quality; Anthocyanin
* Tel.: +46-44-755-46; fax: +46-44-755-30.
E-mail address: [email protected] (N. Jeppsson).
0304-4238/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 3 0 4 - 4 2 3 8 ( 9 9 ) 0 0 0 7 0 - 9
128
N. Jeppsson / Scientia Horticulturae 83 (2000) 127±137
1. Introduction
Black chokeberry (Aronia melanocarpa [Michx] Ell., Rosaceae), native to
eastern North America, is a 0.5±3 m high shrub. The black berries are borne in
clusters and ripen in early September in southern Sweden. Approximately,
17 000 ha of this berry crop were reported to be in production in the 1980s in
Russia for use in jam, juice and wine (Kask, 1987). At BalsgaÊrd, black
chokeberry is being evaluated as a potential new crop for Sweden (Jeppsson,
1999).
Anthocyanin-rich extracts are used as food colourants to improve the appeal of
certain food products, and have partly replaced the formerly used azo-dyes.
Commercial anthocyanin production is based mainly on grape skins but other
sources such as elderberries (Sambucus nigra L.) are also used (Bridle and
Timberlake, 1997) and others including the fruits of black chokeberry have been
mentioned as a source of anthocyanin-rich extracts (Timberlake and Henry, 1988;
Mazza and Miniati, 1993). The berries contain 725±800 mg anthocyanins/100 g
fresh weight (Mazza and Miniati, 1993) and have a low tendency to browning, at
least as compared to elderberry (Plocharski et al., 1989). The anthocyanins in
black chokeberry consist mainly of cyanidin-3-galactoside and cyanidin-3arabinoside, which are reported to constitute 64% and 29%, respectively
(Oszmianski and Sapis, 1988), and are found in the peel as well as throughout the
fruit flesh.
Crop requirements must focus on production of high quality pigment if the
fruits are intended as a source of natural food colourants. High berry yield is of
course desired, whereas berry size is of little consequence for an industrial crop.
Other important parameters are: (1) total anthocyanins in the juice, which should
be as high as possible. Fertilizer application affects the anthocyanin formation in
cranberry (Vaccinium macrocarpon Ait.) (Eaton, 1971; Eck, 1976) and apples
(Saure, 1990; Raese and Drake, 1997); (2) content of brown compounds in the
juice, which should be as low as possible since they may affect the appearance of
fruit products negatively. I have found no data on effects of fertilizers on brown
pigment content in any kind of fruit; (3) juice soluble solids which should be as
low as possible since it determines the limit for the gain in volume decrease when
producing fruit concentrates. In apples the soluble solids can decrease with
increased nitrogen fertilizer rate (Raese and Drake, 1997), whereas no effect was
seen in pears (Raese, 1997); (4) anthocyanin composition since it has been
suggested to play a role in the stability of extracts (Starr and Francis, 1968), and
(5) total acidity which should be high since anthocyanins are more stable in acid
environments (Mazza and Miniati, 1993) and the stability of anthocyanins during
processing is strongly influenced by the pH of the media (Chichester and
McFeeters, 1970).
N. Jeppsson / Scientia Horticulturae 83 (2000) 127±137
129
This investigation was performed to (1) study whether pigment content and
quality of the berries of black chokeberry cv. `Viking' is affected by fertilizer
rate, (2) develop grower recommendations concerning fertilization of black
chokeberry and (3) investigate associations among agronomical and fruit quality
parameters.
2. Materials and methods
2.1. Experimental
The trial was performed at BalsgaÊrd ± Department of Horticultural Plant
Breeding (56807'N, 14810'E), Sweden. The trial site was an apple orchard until
1989, but without any nitrogen application from 1982 to 1989. Between 1989 and
1991 the field lay fallow and in 1991±1992 it was ploughed and treated with
herbicides. The soil is classified as sandy with 2±4% of clay and a pH of 5.5, and
contained 5.6 and 5.2 mg/100 g soil of plant-available P and K, respectively, in
1992. This is well below the values recommended of 8±12 and 14±16,
respectively, for fruit orchards on sandy soils in the region.
Black chokeberry cv. `Viking' rooted cuttings of even size were planted in
October 1992, 1 m apart in rows that were 3.5 m apart. Four treatments (A, B, C
and D), replicated in two blocks giving eight experimental units each comprising
10 plants, of which plants no. 1 and 10 were used as guard plants. Guard rows
also surrounded the trial. Prior to planting, manure corresponding to 18 kg N/ha,
21 kg P/ha and 135 kg K/ha was applied. In 1993, manure in different rates by
weight (times 1.0, 1.5, 2.0 and 3.0 for treatments A, B, C and D, respectively,
with rate A corresponding to 30 kg N/ha, 45 kg P/ha and 150 kg K/ha) were
applied. In 1994±1997, a commercial combined fertilizer was used. The same
rates as in 1993 were used with rate A corresponding to 25 kg N/ha, 22 kg P/ha
and 50 kg K/ha. The fertilizers were applied manually between April 16 and 22
each year. After application, the soil was not disturbed for five weeks. Thereafter
weed control was performed, manually within rows and by harrowing between
rows.
2.2. Weather
Data were obtained for the Kristianstad ± EveroÈd airport approximately 25 km
from the experimental site. In August, during the later stages in fruit
development, the mean temperature was 188C, 188C and 208C for the
years 1995, 1996 and 1997, respectively, whereas the precipitation was 12, 56 and
2 mm, respectively.
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N. Jeppsson / Scientia Horticulturae 83 (2000) 127±137
2.3. Parameters evaluated
Plant height was recorded after cessation of growth. Berries were harvested
when visually estimated to be fully ripe (30±31 August 1995, 11±12 September
1996 and 11 September 1997). Total yield and berry size as the fresh weight of
fifty berries, were measured. Berry samples for analysis were stored at ÿ208C.
Juice was produced from thawed berries with a garlic press to measure
anthocyanins, brown compounds and soluble solids. Anthocyanins were
measured by the pH differential method (Fuleki and Francis, 1968; Wrolstad,
1976) and expressed as cyanidin-3-galactoside using the molar absorbance of
" 30 200 and molecular weight of 445. Brown compounds were measured
according to Wrolstad (1976): a juice sample diluted in distilled water was
bleached with K2S2O5 and browning was registered by absorbance at 420 nm and
expressed as browning index. Absorbances were recorded with a Shimadzu UV2101 PC spectrophotometer. Soluble solids were recorded with a digital
refractometer (Atago, PR-100) and expressed as 8Brix.
Anthocyanin composition was determined by thin layer chromatography (TLC)
according to Nilsson and Trajkovski (1977) with modifications. Pigments were
extracted in methanol (p.a.) with 1% (v/v) concentrated HCl (p.a. Merck) and
separated on one-dimensional TLC using 0.1 mm cellulose plates (Merck) and 1butanol (Kebo), acetic acid (Merck) and distilled water (90 : 15 : 30). The two
spots obtained, here assumed to correspond to cyanidin-3-galactoside and
cyanidin-3-arabinoside on basis of their relative size, were quantified in a CSscanner (Shimadzu CS 9001PC, supported with software v. 3.01). The relative
content of cyanidin-3-galactoside to total anthocyanin content was estimated as
the area of the largest spot divided by the sum of both areas. Acidity was
measured by titration to pH 8.1 with 0.1 M NaOH and expressed as malic acid.
The production of anthocyanins per plant [Acy(T)] was estimated as the
anthocyanin content in the juice sample [Acy (c)] and the assumed (based on own
unpublished observation) juice yield of 0.7 (1/kg):
Acy T Acy c 0:7 Yield:
2.4. Statistical analysis of data
Each of eight plants (no. 2±9) in an experimental unit was measured for height,
berry weight, pigment content, browning index, soluble solids and total acidity in
1995±1997. Yield was based on eight plants in each experimental unit in 1995±
1996 and on the middle six plants in each experimental unit in 1997. Pigment
composition was analysed on each of the middle six plants in each experimental
unit in all three years. To test whether the neighbour treatment affected the
N. Jeppsson / Scientia Horticulturae 83 (2000) 127±137
131
outermost plants (in this case plants no. 2 and 9) in each experimental unit, the
following statistical test was used: in each experimental unit the parameter values
for the eight individual plants were ranked from the lowest to the highest. The
rank values for plant no. 2 and 9 (R2 and R9) in each experimental unit were used
to calculate Ai:
Ai Abs R2 ÿ 4:5 Abs R9 ÿ 4:5:
The test quantity, T, was calculated as the sum of these AiP
. When testing eight
experimental units over three years the critical value for T 24
i1 Ai is 109 at the
5% level.
Testing
eight
experimental
units
for
one
year
the
critical value for
P8
T i1 Ai is 40 at the 5% level. This means that there is a significant effect
from neighbour treatment on the outermost plants when T is larger than or equal
to this critical value.
Average values for each experimental unit were then used to test the effects of
block, year, treatment and the interaction year treatment using analysis of
variance with Super ANOVA v. 1.11. Since the interaction year treatment was
not significant, the analysis was repeated with exclusion of the interaction in the
model. Duncan's Multiple Range Test (Super ANOVA v. 1.11) was used to test
the significance between treatments and years. Associations between the different
characters were determined at the individual plant level by Pearson correlation
tests (SYSTAT v. 5.2.1).
3. Results
Plants no. 2 and 9 in each experimental unit did not differ from the mean for
any parameter except total acidity where T barely exceeded the critical value (111
vs. 109). The mean for each unit measurement was therefore based on all eight
plants for all parameters.
There were no significant effects from block for any of the parameters, but
highly significant variation among years was found for all parameters except total
acidity (Table 1). This was probably due to differences in mean temperature and
precipitation among years, with August 1997 being very dry and having a mean
temperature two degrees higher than the two previous years. In 1997, the lowest
mean berry weight and a remarkable loss in yield (compared to 1996) were
recorded, whereas the highest scores were obtained for both anthocyanin content
and browning.
Significant effects from treatments were found in height (p 0.021), yield
(p 0.012), anthocyanin content (p 0.023) and total acidity (p 0.040). Both
plant growth and yield were promoted by increased fertilizer rate whereas the
anthocyanin production and the total acidity decreased (Table 2). There were no
significant effects from treatments on either browning index (p 0.97), content
132
1995
1996
1997
Height
(cm)
Yield
(g)
Mean berry
weight (g)
Anthocyanin
content (mg/l)
Browning
index (l)
Soluble solids
(8Brix)
Anthocyanin
composition (%)
Total acidity
(g malic acid/100 g)
62a
85b
99c
440a
3030b
1050c
0.77a
0.85b
0.61c
730a
1030b
1530c
0.67a
0.68a
1.19b
17.6a
16.3b
17.8a
67.9a
66.7b
68.3a
0.72a
0.67a
0.70a
N. Jeppsson / Scientia Horticulturae 83 (2000) 127±137
Table 1
The mean treatment values for plant height, yield, mean berry weight, anthocyanin content, browning index, soluble solids, anthocyanin composition
and total acidity compared with Duncan Multiple Range Test for differences among years (in each column, entries with the same letters are not
different at 5% level of significance)
133
N. Jeppsson / Scientia Horticulturae 83 (2000) 127±137
Table 2
The mean three-year-values for height, yield, anthocyanin content and total acidity compared with
Duncan Multiple Range Test for differences among treatments (in each column, entries with the
same letters are not different at 5% level of significance)
Treatment
Height
(cm)
Yield
(g)
Anthocyanin
content
(mg/l)
Total acidity
(g malic
acid/100 g)
Anthocyanin
production
(g/plant)
A
B
C
D
65a
79ab
92b
93b
880a
1260ab
1960b
1910b
1330a
1070ab
1100ab
880b
0.75a
0.70ab
0.69ab
0.65b
2.65a
2.72a
4.62a
3.58a
of soluble solids (p 0.96) or anthocyanin composition (p 0.34). Treatment A
differed significantly from C and D for both plant height and yield, whereas it
differed significantly only from D for anthocyanin content and total acidity.
Treatment C resulted in the highest (however, not significant) total anthocyanin
production per plant in all three years. The increase in yield by increased fertilizer
level did not result in any total increase in anthocyanin production since the crop
produced less anthocyanin per weight unit.
In 1995 and 1996, negative correlations were found between plant height and
both anthocyanin content and total acidity (Table 3). For the same years, positive
correlations were found between plant height and browning index and between
anthocyanin content and total acidity. A positive correlation was found between
plant height and yield in 1996 and 1997. All other correlations were either not
Table 3
Correlation between those parameters among which significant correlations were found in at least
one year
Plant height and yield
Plant height and anthocyanin content
Plant height and browning index
Plant height and total acidity
Yield and anthocyanin content
Berry weight and browning index
Berry weight and total acidity
Anthocyanin content and browning index
Anthocyanin content and soluble solids
Anthocyanin content and total acidity
Browning index and total acidity
*
1995
1996
1997
NS
ÿ0.619***
0.482**
ÿ0.732***
NS
ÿ0.513**
0.551**
ÿ0.488*
NS
0.663***
ÿ0.741***
0.857***
ÿ0.708***
0.504*
ÿ0.553**
ÿ0.553**
NS
NS
NS
NS
0.669***
NS
0.867***
NS
NS
NS
NS
NS
NS
NS
0.463*
NS
NS
Significantly different 5%, with Bonferroni test.
Significantly different at 1%, with Bonferroni test.
***
Significantly different at 0.1% level, with Bonferroni test.
**
134
N. Jeppsson / Scientia Horticulturae 83 (2000) 127±137
significant or significant only in one year. The drought in 1997 probably was the
reason that most correlations recorded in 1995 and 1996 were not repeated in 1997.
4. Discussion
4.1. Plant height and yield
Both plant height and yield showed a simultaneous positive effect from
increased fertilizer rate. By contrast, a negative relationship was found for yield
and growth in cranberry, at least in the first year of cropping, which was
explained as a result of competition (Eck, 1976).
4.2. Anthocyanin content and soluble solids
The negative effect recorded here on anthocyanin content from increased fertilizer
rate in black chokeberry corresponds to previous investigations in apples; among the
soil factors, available nitrogen is believed to be the most important and nitrogen
application can lead to a decrease in colouration (Raese and Drake, 1997). In
cranberry, Eaton (1971) suggested that increased application of nitrogen resulted in
decreased content of red pigments, and Eck (1976) detected a significant decrease in
anthocyanin content as a response to increased nitrogen application, in one year out
of three. On the other hand, Davenport (1996) found no effect of nitrogen fertilizer
level on total anthocyanin content in cranberry.
Shading of the berries due to increased vegetative growth was suggested by
Francis and Atwood (1961) to have caused the decrease in anthocyanin content in
cranberry at high nitrogen fertilizer rate. Since there was a significant correlation
between anthocyanin content and plant height in black chokeberry, shading could
be responsible for the inverse relation between fertilizer rate and anthocyanin content.
Sapers et al. (1986) reported an inverse relationship between fruit size and
anthocyanin content in cranberries. However, the decrease in anthocyanin content
with increased fertilizer rate in black chokeberry cannot be explained by dilution
since fruit weight was not affected by treatment. In addition, the content of
soluble solids was unaffected by treatment. These results agree with data from
blackberry, where both the content of soluble solids and the content of total solids
were unaffected by different nitrogen fertilizer rates (Alleyne and Clark, 1997).
4.3. Browning and total acidity
Browning, which is an important quality trait for any fruit crop, is partly caused
by chemical reactions with phenolic compounds as a substrate. No effect from
fertilizer rate on browning was found in the present experiment. By contrast, there
N. Jeppsson / Scientia Horticulturae 83 (2000) 127±137
135
was a positive correlation between plant height and content of brown compounds
in both 1995 and 1996, indicating that an increased fertilizer rate actually
increases the content of brown compounds.
The decrease in total acidity with increased fertilizer rate cannot be explained
by a dilution effect since mean berry weight remained unaffected as well as the
overall content of soluble solids (cf. anthocyanin content). By contrast, total
acidity was not affected by nitrogen fertilizer rate in either apple or pears (Raese,
1997; Raese and Drake, 1997).
4.4. Anthocyanin composition
Differences in anthocyanin composition may affect pigment stability (Starr and
Francis, 1968) as well as the appearance of the product. In the present
investigation there was no effect from treatments on the relative area of the
anthocyanin spots. Thus it could be concluded that there is no effect on
anthocyanin composition from fertilizer rate. This is in agreement with a previous
investigation on grape cultivars grown at different sites, which showed that the
anthocyanin composition was cultivar specific, and not affected by environmental
factors (Bakker and Timberlake, 1985).
5. Conclusion
For the commercial cultivation of black chokeberry as raw material for food
colourant production, grower recommendations must focus on the optimal
production of anthocyanins per hectare. Yield increased with an increased
fertilizer rate whereas anthocyanin content decreased. Even if the differences
between treatments in anthocyanin production per plant were not significant,
treatments A and D were significantly different for both yield and anthocyanin
content. The resulting anthocyanin production was obtained for the two highest
fertilizer rates (treatment C and D). The significant decrease in total acidity
obtained with an increased fertilizer rate, however, points to the importance of
keeping fertilization at a moderate level in order to favour a high content of
organic acids. In addition by avoiding excessive application of fertilizers, the
farmer makes an economic gain while, at the same time, the environment is
protected from unnecessary fertilizer leakage. Overall it can be concluded that, in
the present study, treatment C was the most beneficial from the growers point of
view and could thus be recommended for black chokeberry production.
Acknowledgements
Technical assistance was given by Pia Barnekow, Daniel Ehmann, Stefan
Ê berg. Jan-Eric Englund developed the model for testing the
Olsson and Fredrik A
136
N. Jeppsson / Scientia Horticulturae 83 (2000) 127±137
effect from neighbour treatment on the outermost plants. Hilde Nybom and
Gustav Redalen gave valuable comments on the manuscript. Financial support
was received from The Swedish Board for Technical Development and the
Swedish Research Council for Forestry and Agriculture.
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The effects of fertilizer rate on vegetative growth, yield
and fruit quality, with special respect to pigments, in
black chokeberry (Aronia melanocarpa) cv. `Viking'
Niklas Jeppsson*
BalsgaÊrd-Department of Horticultural Plant Breeding, Swedish University of Agricultural Sciences,
FjaÈlkestadsvaÈgen 123-1, S-291 94 Kristianstad, Sweden
Accepted 6 May 1999
Abstract
The effect of fertilizer rate on fruit quality parameters in the black chokeberry (Aronia
melanocarpa [Michx] Ell.) cv. `Viking' was studied over three years. A combined N±P±K fertilizer
was applied in different rates. Plant height, yield, berry weight, anthocyanin content, content of
brown compounds, content of soluble solids, anthocyanin composition and total acidity were
recorded for the different treatments. Increased application of fertilizers resulted in increased
vegetative growth and yield whereas the content of anthocyanins and total acidity decreased. Mean
berry weight, content of brown compounds, soluble solids and anthocyanin composition were
unaffected. Correlations between the different parameters were calculated at single plant level.
Positive correlations were found between plant height and yield, between plant height and browning
index, and between anthocyanin content and total acidity. Negative correlations were found
between plant height on one hand, and anthocyanin content and total acidity on the other hand. It
was concluded that an increased fertilizer application results in increased growth and higher yield
whereas pigment content and total acidity decrease. Maximum production of anthocyanins per plant
was obtained with a medium high fertilizer rate (50 kg N/ha, 44 kg P/ha, 100 kg K/ha). # 2000
Elsevier Science B.V. All rights reserved.
Keywords: Rosaceae; Aronia; Fertilizer; Yield; Fruit quality; Anthocyanin
* Tel.: +46-44-755-46; fax: +46-44-755-30.
E-mail address: [email protected] (N. Jeppsson).
0304-4238/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 3 0 4 - 4 2 3 8 ( 9 9 ) 0 0 0 7 0 - 9
128
N. Jeppsson / Scientia Horticulturae 83 (2000) 127±137
1. Introduction
Black chokeberry (Aronia melanocarpa [Michx] Ell., Rosaceae), native to
eastern North America, is a 0.5±3 m high shrub. The black berries are borne in
clusters and ripen in early September in southern Sweden. Approximately,
17 000 ha of this berry crop were reported to be in production in the 1980s in
Russia for use in jam, juice and wine (Kask, 1987). At BalsgaÊrd, black
chokeberry is being evaluated as a potential new crop for Sweden (Jeppsson,
1999).
Anthocyanin-rich extracts are used as food colourants to improve the appeal of
certain food products, and have partly replaced the formerly used azo-dyes.
Commercial anthocyanin production is based mainly on grape skins but other
sources such as elderberries (Sambucus nigra L.) are also used (Bridle and
Timberlake, 1997) and others including the fruits of black chokeberry have been
mentioned as a source of anthocyanin-rich extracts (Timberlake and Henry, 1988;
Mazza and Miniati, 1993). The berries contain 725±800 mg anthocyanins/100 g
fresh weight (Mazza and Miniati, 1993) and have a low tendency to browning, at
least as compared to elderberry (Plocharski et al., 1989). The anthocyanins in
black chokeberry consist mainly of cyanidin-3-galactoside and cyanidin-3arabinoside, which are reported to constitute 64% and 29%, respectively
(Oszmianski and Sapis, 1988), and are found in the peel as well as throughout the
fruit flesh.
Crop requirements must focus on production of high quality pigment if the
fruits are intended as a source of natural food colourants. High berry yield is of
course desired, whereas berry size is of little consequence for an industrial crop.
Other important parameters are: (1) total anthocyanins in the juice, which should
be as high as possible. Fertilizer application affects the anthocyanin formation in
cranberry (Vaccinium macrocarpon Ait.) (Eaton, 1971; Eck, 1976) and apples
(Saure, 1990; Raese and Drake, 1997); (2) content of brown compounds in the
juice, which should be as low as possible since they may affect the appearance of
fruit products negatively. I have found no data on effects of fertilizers on brown
pigment content in any kind of fruit; (3) juice soluble solids which should be as
low as possible since it determines the limit for the gain in volume decrease when
producing fruit concentrates. In apples the soluble solids can decrease with
increased nitrogen fertilizer rate (Raese and Drake, 1997), whereas no effect was
seen in pears (Raese, 1997); (4) anthocyanin composition since it has been
suggested to play a role in the stability of extracts (Starr and Francis, 1968), and
(5) total acidity which should be high since anthocyanins are more stable in acid
environments (Mazza and Miniati, 1993) and the stability of anthocyanins during
processing is strongly influenced by the pH of the media (Chichester and
McFeeters, 1970).
N. Jeppsson / Scientia Horticulturae 83 (2000) 127±137
129
This investigation was performed to (1) study whether pigment content and
quality of the berries of black chokeberry cv. `Viking' is affected by fertilizer
rate, (2) develop grower recommendations concerning fertilization of black
chokeberry and (3) investigate associations among agronomical and fruit quality
parameters.
2. Materials and methods
2.1. Experimental
The trial was performed at BalsgaÊrd ± Department of Horticultural Plant
Breeding (56807'N, 14810'E), Sweden. The trial site was an apple orchard until
1989, but without any nitrogen application from 1982 to 1989. Between 1989 and
1991 the field lay fallow and in 1991±1992 it was ploughed and treated with
herbicides. The soil is classified as sandy with 2±4% of clay and a pH of 5.5, and
contained 5.6 and 5.2 mg/100 g soil of plant-available P and K, respectively, in
1992. This is well below the values recommended of 8±12 and 14±16,
respectively, for fruit orchards on sandy soils in the region.
Black chokeberry cv. `Viking' rooted cuttings of even size were planted in
October 1992, 1 m apart in rows that were 3.5 m apart. Four treatments (A, B, C
and D), replicated in two blocks giving eight experimental units each comprising
10 plants, of which plants no. 1 and 10 were used as guard plants. Guard rows
also surrounded the trial. Prior to planting, manure corresponding to 18 kg N/ha,
21 kg P/ha and 135 kg K/ha was applied. In 1993, manure in different rates by
weight (times 1.0, 1.5, 2.0 and 3.0 for treatments A, B, C and D, respectively,
with rate A corresponding to 30 kg N/ha, 45 kg P/ha and 150 kg K/ha) were
applied. In 1994±1997, a commercial combined fertilizer was used. The same
rates as in 1993 were used with rate A corresponding to 25 kg N/ha, 22 kg P/ha
and 50 kg K/ha. The fertilizers were applied manually between April 16 and 22
each year. After application, the soil was not disturbed for five weeks. Thereafter
weed control was performed, manually within rows and by harrowing between
rows.
2.2. Weather
Data were obtained for the Kristianstad ± EveroÈd airport approximately 25 km
from the experimental site. In August, during the later stages in fruit
development, the mean temperature was 188C, 188C and 208C for the
years 1995, 1996 and 1997, respectively, whereas the precipitation was 12, 56 and
2 mm, respectively.
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N. Jeppsson / Scientia Horticulturae 83 (2000) 127±137
2.3. Parameters evaluated
Plant height was recorded after cessation of growth. Berries were harvested
when visually estimated to be fully ripe (30±31 August 1995, 11±12 September
1996 and 11 September 1997). Total yield and berry size as the fresh weight of
fifty berries, were measured. Berry samples for analysis were stored at ÿ208C.
Juice was produced from thawed berries with a garlic press to measure
anthocyanins, brown compounds and soluble solids. Anthocyanins were
measured by the pH differential method (Fuleki and Francis, 1968; Wrolstad,
1976) and expressed as cyanidin-3-galactoside using the molar absorbance of
" 30 200 and molecular weight of 445. Brown compounds were measured
according to Wrolstad (1976): a juice sample diluted in distilled water was
bleached with K2S2O5 and browning was registered by absorbance at 420 nm and
expressed as browning index. Absorbances were recorded with a Shimadzu UV2101 PC spectrophotometer. Soluble solids were recorded with a digital
refractometer (Atago, PR-100) and expressed as 8Brix.
Anthocyanin composition was determined by thin layer chromatography (TLC)
according to Nilsson and Trajkovski (1977) with modifications. Pigments were
extracted in methanol (p.a.) with 1% (v/v) concentrated HCl (p.a. Merck) and
separated on one-dimensional TLC using 0.1 mm cellulose plates (Merck) and 1butanol (Kebo), acetic acid (Merck) and distilled water (90 : 15 : 30). The two
spots obtained, here assumed to correspond to cyanidin-3-galactoside and
cyanidin-3-arabinoside on basis of their relative size, were quantified in a CSscanner (Shimadzu CS 9001PC, supported with software v. 3.01). The relative
content of cyanidin-3-galactoside to total anthocyanin content was estimated as
the area of the largest spot divided by the sum of both areas. Acidity was
measured by titration to pH 8.1 with 0.1 M NaOH and expressed as malic acid.
The production of anthocyanins per plant [Acy(T)] was estimated as the
anthocyanin content in the juice sample [Acy (c)] and the assumed (based on own
unpublished observation) juice yield of 0.7 (1/kg):
Acy T Acy c 0:7 Yield:
2.4. Statistical analysis of data
Each of eight plants (no. 2±9) in an experimental unit was measured for height,
berry weight, pigment content, browning index, soluble solids and total acidity in
1995±1997. Yield was based on eight plants in each experimental unit in 1995±
1996 and on the middle six plants in each experimental unit in 1997. Pigment
composition was analysed on each of the middle six plants in each experimental
unit in all three years. To test whether the neighbour treatment affected the
N. Jeppsson / Scientia Horticulturae 83 (2000) 127±137
131
outermost plants (in this case plants no. 2 and 9) in each experimental unit, the
following statistical test was used: in each experimental unit the parameter values
for the eight individual plants were ranked from the lowest to the highest. The
rank values for plant no. 2 and 9 (R2 and R9) in each experimental unit were used
to calculate Ai:
Ai Abs R2 ÿ 4:5 Abs R9 ÿ 4:5:
The test quantity, T, was calculated as the sum of these AiP
. When testing eight
experimental units over three years the critical value for T 24
i1 Ai is 109 at the
5% level.
Testing
eight
experimental
units
for
one
year
the
critical value for
P8
T i1 Ai is 40 at the 5% level. This means that there is a significant effect
from neighbour treatment on the outermost plants when T is larger than or equal
to this critical value.
Average values for each experimental unit were then used to test the effects of
block, year, treatment and the interaction year treatment using analysis of
variance with Super ANOVA v. 1.11. Since the interaction year treatment was
not significant, the analysis was repeated with exclusion of the interaction in the
model. Duncan's Multiple Range Test (Super ANOVA v. 1.11) was used to test
the significance between treatments and years. Associations between the different
characters were determined at the individual plant level by Pearson correlation
tests (SYSTAT v. 5.2.1).
3. Results
Plants no. 2 and 9 in each experimental unit did not differ from the mean for
any parameter except total acidity where T barely exceeded the critical value (111
vs. 109). The mean for each unit measurement was therefore based on all eight
plants for all parameters.
There were no significant effects from block for any of the parameters, but
highly significant variation among years was found for all parameters except total
acidity (Table 1). This was probably due to differences in mean temperature and
precipitation among years, with August 1997 being very dry and having a mean
temperature two degrees higher than the two previous years. In 1997, the lowest
mean berry weight and a remarkable loss in yield (compared to 1996) were
recorded, whereas the highest scores were obtained for both anthocyanin content
and browning.
Significant effects from treatments were found in height (p 0.021), yield
(p 0.012), anthocyanin content (p 0.023) and total acidity (p 0.040). Both
plant growth and yield were promoted by increased fertilizer rate whereas the
anthocyanin production and the total acidity decreased (Table 2). There were no
significant effects from treatments on either browning index (p 0.97), content
132
1995
1996
1997
Height
(cm)
Yield
(g)
Mean berry
weight (g)
Anthocyanin
content (mg/l)
Browning
index (l)
Soluble solids
(8Brix)
Anthocyanin
composition (%)
Total acidity
(g malic acid/100 g)
62a
85b
99c
440a
3030b
1050c
0.77a
0.85b
0.61c
730a
1030b
1530c
0.67a
0.68a
1.19b
17.6a
16.3b
17.8a
67.9a
66.7b
68.3a
0.72a
0.67a
0.70a
N. Jeppsson / Scientia Horticulturae 83 (2000) 127±137
Table 1
The mean treatment values for plant height, yield, mean berry weight, anthocyanin content, browning index, soluble solids, anthocyanin composition
and total acidity compared with Duncan Multiple Range Test for differences among years (in each column, entries with the same letters are not
different at 5% level of significance)
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N. Jeppsson / Scientia Horticulturae 83 (2000) 127±137
Table 2
The mean three-year-values for height, yield, anthocyanin content and total acidity compared with
Duncan Multiple Range Test for differences among treatments (in each column, entries with the
same letters are not different at 5% level of significance)
Treatment
Height
(cm)
Yield
(g)
Anthocyanin
content
(mg/l)
Total acidity
(g malic
acid/100 g)
Anthocyanin
production
(g/plant)
A
B
C
D
65a
79ab
92b
93b
880a
1260ab
1960b
1910b
1330a
1070ab
1100ab
880b
0.75a
0.70ab
0.69ab
0.65b
2.65a
2.72a
4.62a
3.58a
of soluble solids (p 0.96) or anthocyanin composition (p 0.34). Treatment A
differed significantly from C and D for both plant height and yield, whereas it
differed significantly only from D for anthocyanin content and total acidity.
Treatment C resulted in the highest (however, not significant) total anthocyanin
production per plant in all three years. The increase in yield by increased fertilizer
level did not result in any total increase in anthocyanin production since the crop
produced less anthocyanin per weight unit.
In 1995 and 1996, negative correlations were found between plant height and
both anthocyanin content and total acidity (Table 3). For the same years, positive
correlations were found between plant height and browning index and between
anthocyanin content and total acidity. A positive correlation was found between
plant height and yield in 1996 and 1997. All other correlations were either not
Table 3
Correlation between those parameters among which significant correlations were found in at least
one year
Plant height and yield
Plant height and anthocyanin content
Plant height and browning index
Plant height and total acidity
Yield and anthocyanin content
Berry weight and browning index
Berry weight and total acidity
Anthocyanin content and browning index
Anthocyanin content and soluble solids
Anthocyanin content and total acidity
Browning index and total acidity
*
1995
1996
1997
NS
ÿ0.619***
0.482**
ÿ0.732***
NS
ÿ0.513**
0.551**
ÿ0.488*
NS
0.663***
ÿ0.741***
0.857***
ÿ0.708***
0.504*
ÿ0.553**
ÿ0.553**
NS
NS
NS
NS
0.669***
NS
0.867***
NS
NS
NS
NS
NS
NS
NS
0.463*
NS
NS
Significantly different 5%, with Bonferroni test.
Significantly different at 1%, with Bonferroni test.
***
Significantly different at 0.1% level, with Bonferroni test.
**
134
N. Jeppsson / Scientia Horticulturae 83 (2000) 127±137
significant or significant only in one year. The drought in 1997 probably was the
reason that most correlations recorded in 1995 and 1996 were not repeated in 1997.
4. Discussion
4.1. Plant height and yield
Both plant height and yield showed a simultaneous positive effect from
increased fertilizer rate. By contrast, a negative relationship was found for yield
and growth in cranberry, at least in the first year of cropping, which was
explained as a result of competition (Eck, 1976).
4.2. Anthocyanin content and soluble solids
The negative effect recorded here on anthocyanin content from increased fertilizer
rate in black chokeberry corresponds to previous investigations in apples; among the
soil factors, available nitrogen is believed to be the most important and nitrogen
application can lead to a decrease in colouration (Raese and Drake, 1997). In
cranberry, Eaton (1971) suggested that increased application of nitrogen resulted in
decreased content of red pigments, and Eck (1976) detected a significant decrease in
anthocyanin content as a response to increased nitrogen application, in one year out
of three. On the other hand, Davenport (1996) found no effect of nitrogen fertilizer
level on total anthocyanin content in cranberry.
Shading of the berries due to increased vegetative growth was suggested by
Francis and Atwood (1961) to have caused the decrease in anthocyanin content in
cranberry at high nitrogen fertilizer rate. Since there was a significant correlation
between anthocyanin content and plant height in black chokeberry, shading could
be responsible for the inverse relation between fertilizer rate and anthocyanin content.
Sapers et al. (1986) reported an inverse relationship between fruit size and
anthocyanin content in cranberries. However, the decrease in anthocyanin content
with increased fertilizer rate in black chokeberry cannot be explained by dilution
since fruit weight was not affected by treatment. In addition, the content of
soluble solids was unaffected by treatment. These results agree with data from
blackberry, where both the content of soluble solids and the content of total solids
were unaffected by different nitrogen fertilizer rates (Alleyne and Clark, 1997).
4.3. Browning and total acidity
Browning, which is an important quality trait for any fruit crop, is partly caused
by chemical reactions with phenolic compounds as a substrate. No effect from
fertilizer rate on browning was found in the present experiment. By contrast, there
N. Jeppsson / Scientia Horticulturae 83 (2000) 127±137
135
was a positive correlation between plant height and content of brown compounds
in both 1995 and 1996, indicating that an increased fertilizer rate actually
increases the content of brown compounds.
The decrease in total acidity with increased fertilizer rate cannot be explained
by a dilution effect since mean berry weight remained unaffected as well as the
overall content of soluble solids (cf. anthocyanin content). By contrast, total
acidity was not affected by nitrogen fertilizer rate in either apple or pears (Raese,
1997; Raese and Drake, 1997).
4.4. Anthocyanin composition
Differences in anthocyanin composition may affect pigment stability (Starr and
Francis, 1968) as well as the appearance of the product. In the present
investigation there was no effect from treatments on the relative area of the
anthocyanin spots. Thus it could be concluded that there is no effect on
anthocyanin composition from fertilizer rate. This is in agreement with a previous
investigation on grape cultivars grown at different sites, which showed that the
anthocyanin composition was cultivar specific, and not affected by environmental
factors (Bakker and Timberlake, 1985).
5. Conclusion
For the commercial cultivation of black chokeberry as raw material for food
colourant production, grower recommendations must focus on the optimal
production of anthocyanins per hectare. Yield increased with an increased
fertilizer rate whereas anthocyanin content decreased. Even if the differences
between treatments in anthocyanin production per plant were not significant,
treatments A and D were significantly different for both yield and anthocyanin
content. The resulting anthocyanin production was obtained for the two highest
fertilizer rates (treatment C and D). The significant decrease in total acidity
obtained with an increased fertilizer rate, however, points to the importance of
keeping fertilization at a moderate level in order to favour a high content of
organic acids. In addition by avoiding excessive application of fertilizers, the
farmer makes an economic gain while, at the same time, the environment is
protected from unnecessary fertilizer leakage. Overall it can be concluded that, in
the present study, treatment C was the most beneficial from the growers point of
view and could thus be recommended for black chokeberry production.
Acknowledgements
Technical assistance was given by Pia Barnekow, Daniel Ehmann, Stefan
Ê berg. Jan-Eric Englund developed the model for testing the
Olsson and Fredrik A
136
N. Jeppsson / Scientia Horticulturae 83 (2000) 127±137
effect from neighbour treatment on the outermost plants. Hilde Nybom and
Gustav Redalen gave valuable comments on the manuscript. Financial support
was received from The Swedish Board for Technical Development and the
Swedish Research Council for Forestry and Agriculture.
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