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CHILEAN JOURNAL OF AGRICULTURAL RESEARCH 76(2) APRIL-JUNE 2016
Organic farming does not allow using certain inputs, such
as N, which differ in nutrient release rates and dynamics.
To evaluate the effect of different organic fertilizers on
the vegetative, nutritional, and productive parameters of
blueberries (Vaccinium corymbosum L.), a pot experiment
was conducted in three consecutive seasons in a sandy
soil of south-central Chile using ‘Corona’, ‘Legacy’
and ‘Liberty’. The following fertilizers were evaluated:
compost (CM), Purely Grow (PG), Purely Lysine (PL),
Fertil (F), blood meal (BM), lupine meal (LM), along
with a control treatment without fertilization (C) and two
conventional treatments with urea (CF) and sodium nitrate
(S). Results indicate that vegetative growth and leaf N
concentration prior to senescence were different among
cultivars in the three evaluated seasons. The highest leaf
N concentration was recorded in ‘Corona’ followed by
‘Legacy’ and ‘Liberty’ while levels tended to increase in
the seasons. Quick-release N sources had greater effects
on these parameters but with differences among cultivars.
Fruit yield and weight were higher in ‘Corona’ followed
by ‘Legacy’ and ‘Liberty’. Fruit yield was generally higher
when using LM and F and showed no effect on fruit
weight. Leaf chlorophyll content was higher in ‘Corona’
followed by ‘Legacy’ and ‘Liberty’, which increased when
using CF, LM, BM, and PG. Finally, the organic fertilizer
and blueberry cultivar that obtained the highest values for
most of the evaluated parameters were LM and Corona,
respectively.
Key words: Blueberry, growth and production, nitrogen,
organic fertilization, Vaccinium corymbosum.
ABSTRACT
Effects of organic fertilizers on the
vegetative, nutritional, and productive
parameters of blueberries ‘Corona’,
‘Legacy’, and ‘Liberty’
Pablo Muñoz-Vega1, Hernán Paillán2, Humberto Serri1, Denise Donnay3,
Carlos Sanhueza3, Emilio Merino3, and Juan Hirzel4*
RESEARCH
1Universidad de Concepción, Facultad de Agronomía, Avenida Vicente
Méndez 595, Chillán, Chile.
2Universidad de Talca, Facultad de Ciencias Agrarias, Avenida Lircay
S/N, Talca, Chile.
3Hortifrut S.A., Avenida del Cóndor 600, Huechuraba, Santiago, Chile.
4Instituto de Investigaciones Agropecuarias, INIA Quilamapu, Avenida
Vicente Méndez 515, Chillán, Chile.
*Corresponding author (jhirzel@inia.cl).
Received: 16 September 2015.
Accepted: 13 January 2016.
doi:10.4067/S0718-58392016000200010
RESEARCH
INTRODUCTION
The rst blueberry (Vaccinium corymbosum L.) plants were
introduced in Chile during the 80s to evaluate its potential in
the region. Since then, blueberry production has grown very
quickly with the largest plantation areas concentrated in central
and southern Chile (Bañados, 2006). It has been determined that
blueberries reach their maximum production potential when certain
factors are controlled, such as planting density (Strik and Buller,
2005), variety (Bryla and Strik, 2007), irrigation management
(Bryla et al., 2006), fertilization (Hanson, 2006), weed control
(Krewer et al., 2009), and pH (Burkhard et al., 2009). According
to Strik (2014), there were 77 290 ha of blueberries worldwide in
2010, mainly in the USA (46%) followed by Chile (17%). The
same author reports that the area of organically-grown blueberries
was 4156 ha in the USA and 1600 ha in Chile.
Organic farming techniques to grow crops have gained popularity
in recent years as a result of an increasing consumer demand for
organic products and farmers’ commitment to soil conservation
(Brazelton and Strik, 2007; Larco et al., 2013). According to Lester
(2006), the production of organic food is steadily growing due to a
higher demand for this type of food, which dates back to 1900; the
main markets are the USA and Germany. Despite this increasing
demand, there are still many problems when comparing nutrient
sources in organic and conventional farming systems, mainly
because of the difculty to control all the variables involved
(Lester, 2006).
Soil total N content under organic management increases steadily
when fertilization is applied; it also increases by incorporating
cover crops, peat, compost, shmeal, humus, and N-rich fertilizers
due to the accumulation of both N and C in organic compounds
(Wang et al., 2008). These natural nutrients promote the growth
of benecial soil microorganisms, decompose biomass, and
indirectly provide N, P, K, and other nutrients available to plants
through the crop rhizosphere (Wang et al., 2008). The mixture
of livestock manure and bedding straw can be a suitable nutrient
source for blueberries. The nutrient content of manure should be
well estimated to determine proper application rates. Nevertheless,
the nutrient composition of manure varies depending on the animal
species and other variables, such as management and handling,
which do not allow homogeneous applications (Kozinski, 2006;
Larco, 2010; Larco et al., 2013).
After crops have been established, the major concern in organic
production is the application of N sources because N availability
is highly related to productivity (Miller et al., 2006). Organic
CHILEAN JOURNAL OF AGRICULTURAL RESEARCH 76(2) APRIL-JUNE 2016
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CHILEAN JOURNAL OF AGRICULTURAL RESEARCH 76(2) APRIL-JUNE 2016
fertilizers are usually less soluble than inorganic fertilizers.
Based on this, organic fertilizers should be applied 1 to 4
wk earlier than the recommended time for the application
of inorganic fertilizers (soluble) (Gale et al., 2006). All
ammoniacal N and 25% to 50% of organic N is available
for blueberry plants during the same year it is applied.
Therefore, N rates should be increased by 50% to 100%
when organic materials are used because microorganisms x
a signicant fraction of N (Bañados et al., 2012; Vargas and
Bryla, 2015). Regarding this, other authors have indicated
that despite a slower release of organic N sources, remaining
N from previous seasons provides residual N release similar
to the amount of N applied in every season (Retamales and
Hancock, 2012).
The main sources of N for organic farming are compost,
green manures, natural fertilizers, and residues from
biological processes, so that total N release in plant-available
forms is related to the mineralization capacity of the soil
along with nutritional factors (energy, C and N content,
among others) and soil factors (temperature, moisture,
oxygen, acidity) as reported by several authors (Tamada,
2004; Hanson, 2006; Bañados et al., 2012; Hirzel et al., 2012;
Retamales and Hancock, 2012). When the required data is
collected, prediction equations can be used to determine the
release of N and other nutrients. Therefore, based on the
lack of information about the nutritional management of
organic N in blueberries, a study was conducted to determine
vegetative, nutritional, and productive response to different
organic N sources of three different early-, mid-, and late-
fruiting blueberry cultivars.
MATERIALS AND METHODS
An experiment was established on 15 October 2011 and
conducted in Los Ángeles (37º26’ S, 72º31’ W, 103 m a.s.l.)
in the Biobío Region, Chile. Mean annual rainfall reaches
1093 mm and there is a 5-mo dry period. Summers are warm
and winters are moderately cold with a frost-free period of
235 d and a mean of nine annual frosts. Annual degree-days
reach 1593 while chilling hours reach 1237.
Meristematic plants were planted in 50-L pots with a
density of 5000 plants ha-1, which was higher than the 5 L
volume used by Crisóstomo et al. (2014). Pot soil was sandy
loam composed of 40.5% sand, 43.2% silt, and 16.3% clay
(Aquic Haploxerolls, CIREN, 1999). It had 5.6% organic
matter and 6.16 water pH. Contents of N, P, K, and S were
31, 13, 187, and 12.8 mg kg-1, respectively (Sadzawka et
al., 2004). Water reposition during spring and summer was
conducted with an irrigation system using two emitters of
2.1 L-1 each per plant, which was based on 66% reposition of
daily evapotranspiration (Holzapfel et al., 2004); there were
three irrigation events per week of 2 h d-1 for 6 mo (October
to March) for a total of 300 mm of irrigation per season. To
determine evapotranspiration, an evaporation pan reference
was located on the experimental site.
Three varieties of blueberries were evaluated: ‘Corona’,
‘Legacy’, and ‘Liberty’. These varieties are early-, mi-,
and late-fruiting, respectively, in this agro-climatic zone.
Flower buds were removed in the rst year to avoid fruit
production in the rst season. The following treatments were
applied during the 2011-2012, 2012-2013, and 2013-2014
seasons: 1) No fertilizer application (C) as an indicator of
soil nutrient supply, 2) local compost (CM) (N:P2O5:K2O;
0.84:0.80:0.45 and C:N ratio 11.96) as powder, 3) Fertil (F)
(N:P2O5:K2O; 12.0:0.0:0.0 and C:N ratio 7.60) as pellets,
4) Purely Grow (PG) (N:P2O5:K2O; 13.1:0.0:4.0 and C:N
ratio 6.20) as liquid, 5) Purely Lysine (PL) (N:P2O5:K2O;
15.5:0.0:0.0 and C:N ratio 5.80) as pellets, 6) sodium nitrate
(S) (N:P2O5:K2O; 15.0:0.0:9.0) as granules, 7) blood meal
(BM) (N:P2O5:K2O; 14.5:0.27:0.6 and C:N ratio 3.74) as
powder, 8) lupine meal (LM) (N:P2O5:K2O; 7.93:0.90:1.00
and C:N ratio 5.67) as broken grain, and 9) urea, triple
superphosphate, and potassium sulfate (CF) (N:P2O5:K2O;
45.0:15.8:29.7) as granules. Total N rates were calculated for
80 kg ha-1 rate in the rst year and 100 kg ha-1 in years 2 and 3.
The indicated N rate was divided into three fractions (except
for compost application) and applied in early October (50%)
(beginning of vegetative growth), early December (25%)
(60% to 70% vegetative growth), and at the end of January
(25%) (80% to 90% vegetative growth). Compost was not
split because this organic fertilizer is applied only once in a
real management situation and its N mineralization is slow
(Hirzel et al., 2012). For CF, P and K were applied at rates
of 35 and 66 kg ha-1 P2O5 and K2O, respectively (Bañados et
al., 2012), which also allowed generating conditions without
limiting these nutrients in accordance with the soil chemical
properties used in this study. Fertilizers were applied at a
distance from the blueberry plants and delineated a peripheral
ring. Technical information about the N release speed of the
evaluated fertilizers has been presented by Hirzel (2014);
this report indicated that release to CF was fast for S, PG,
PL, and F while there was medium release to LM and BM
and slow release to CM.
Leaves were collected in May of each year during
the dormant period or close to abscission based on eld
observations to determine both DM and N accumulation prior
to leaf fall as an indicator of N recovery efciency in each
treatment. These samples were weighed to determine fresh
weight and leaf development of each variety. In addition, each
sample was dried in an oven at 70 °C to constant weight and
the dry weight of each sample was determined. A subsample
of each tissue was ground and sieved through a 40 mesh sieve
(0.42 mm openings) to measure the concentrations of total N
by acid digestion and Kjeldahl distillation and titration. Leaf
N extraction was determined by its DM and N concentration
(N extraction = DM (g plant-1) × N concentration (%/100)).
A SPAD-502 instrument (Minolta, Spectrum Technologies,
Plain Field, Illinois, USA) was used in December 2013 to
measure the level of chlorophyll present in leaves of third
medium of each treatment in the three varieties under
study. This measurement was taken at 11:00 h. During
May 2013 and 2014, both the number and length of basal
shoots were determined. The number of lateral shoots and
the sum of their lengths were also determined to estimate
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CHILEAN JOURNAL OF AGRICULTURAL RESEARCH 76(2) APRIL-JUNE 2016
plant vegetative growth. Plants were pruned during winter
dormancy in 2012 and 2013. All fruit buds were removed in
2012, and pruning in 2013 was done using the equilibrium
between both vegetative and reproductive bud as a guideline,
which allowed appropriate vegetative development and
productivity. In 2013, pruning after the rst year of fruit
production was conducted so that ower buds were left for
fruit production according to the vegetative development of
each treatment.
‘Corona’, ‘Legacy’, and ‘Liberty’ blueberries were
collected manually. Fruit yield, weight, and size were
determined at harvest from December 2013 to February
2014 in accordance with fruit ripeness. Fruit color was used
as the harvest index. A randomized complete block design
with a split-plot arrangement was used; the main plot was
the cultivar and the subplot was the N source with four
replicates per treatment, one plant per pot, and three plants
per experimental unit. The season was considered as an
independent variable, so statistical analysis between seasons
was not considered. ANOVA, mean separation test (Tukey),
and separation of interactions by contrasts were performed
at the 5% signicance level with SAS 6.0 (SAS Institute,
Cary, North Carolina, USA). Contrast analyses were used to
separate the interactions.
RESULTS
All evaluated parameters were affected by the cultivar (p <
0.001), with the exception of leaf N concentration that was
estimated in February 2012 (Table 1). Similarly, N sources
also affected all the evaluated parameters (p < 0.001 and p <
0.01), with the exception of the number of basal shoots per
plant that was determined in the 2012-2013 season (Table 1).
Signicant effects were observed in the cultivar × N source
interaction with respect to the sum of lengths of lateral and
basal shoots in the 2013-2014 season and fruit weight from
the rst harvest (p < 0.05) (Table 1). In addition, highly
signicant effects (p < 0.01 and p < 0.001) were observed
in the Cultivar × N Source interaction with respect to leaf N
concentration in February 2012, number of lateral shoots per
plant in the 2012-2013 season, sum of lengths of lateral shoots
in the 2012-2013 season, leaf dry weight in May 2013, leaf N
extraction in May 2013, SPAD units measured in December
2013, fruit yield in the rst harvest, leaf N concentration
in February 2014, leaf dry weight in May 2014, and leaf
N extraction in May 2014 (Table 1). Interactions generally
responded to differences between cultivars and N sources,
which were separated by contrast analysis. These variability
effects are explained by the N source in most of the evaluated
parameters (Tables 2 and 3, Figures 1, 2, 3, and 4).
The number of evaluated basal shoots in the 2012-2013
season was higher in ‘Liberty’ with 4.6 basal shoots (p <
0.05) followed by ‘Legacy’ and ‘Corona’ with 3.8 and 3.5
basal shoots, respectively (Table 2). The sum of lengths of
all basal shoots during the 2012-2013 season was higher in
‘Liberty’ and ‘Legacy’ (p < 0.05) with values of 184.8 and
167.2 cm plant-1, respectively; the value recorded in ‘Corona’
was lower (p < 0.05) and reached 129.5 cm plant-1 (Table 2).
Regarding N sources, LM had the highest value for the sum
of lengths of basal shoots with a mean value of 218.3 cm
plant-1. This value was higher than those recorded in C and
PG (p < 0.05) with mean values that reached 130.1 and 135.9
cm plant-1, respectively (Table 3).
The highest number of lateral shoots per plant was
recorded by ‘Corona’ (p < 0.05) followed by ‘Liberty’ (p <
0.05) and ‘Legacy’ for the 2012-2013 season with values of
34.6, 17.9, and 12.4 shoots plant-1, respectively (Table 2). The
highest N source values were obtained by using F, PG, PL,
Leaf N concentration, g kg-1 (February 2012) NS *** **
Leaf dry weight, g plant-1 (May 2012) *** *** NS
Leaf N extraction, mg plant-1 (May 2012) *** *** NS
Number of lateral shoots per plant, 2012-2013 *** *** **
Number of basal shoots per plant, 2012-2013 ** NS NS
Sum (cm) of the lengths of lateral shoots, cm plant-1 (2012-2013) *** *** ***
Sum of the lengths of basal shoots, cm plant-1 (2012-2013) *** ** NS
Leaf N concentration, g kg-1 (May 2013) *** *** NS
Leaf dry weight, g plant-1 (May 2013) *** *** ***
Leaf N extraction, mg plant-1 (May 2013) *** *** ***
SPAD (unit), December 2013 *** *** ***
Number of lateral shoots per plant, 2013-2014 *** *** NS
Number of basal shoots per plant, 2013-2014 *** *** NS
Sum (cm) of the lengths of lateral shoots 2013-2014 *** *** *
Sum (cm) of the lengths of basal shoots 2013-2014 *** *** *
Fruit weight, g *** ** *
Yield, g plant-1 *** *** **
Leaf N concentration, g kg-1, (May 2014) *** *** ***
Leaf dry weight, g plant-1, (May 2014) *** *** ***
Leaf N extraction, mg plant-1 (May 2014) *** *** ***
Table 1. Signicance analysis of parameters for vegetative and nutritional growth evaluated in ‘Corona’, ‘Legacy’ and ‘Liberty’
blueberries with different N sources during the 2012-2013 and 2013-2014 seasons.
Source of variation
*, **, *** Signicant at probability levels of 0.05, 0.01, and 0.001. NS: nonsignicant.
Cultivars
(C)
Nitrogen sources
(N)
Interaction
(C×N)
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CHILEAN JOURNAL OF AGRICULTURAL RESEARCH 76(2) APRIL-JUNE 2016
BM, LM, and CF. Values showed no signicant differences
among them (p > 0.05) and were only higher than the value
obtained for S (p < 0.05) (Table 3).
The values of the sum of lengths of lateral shoots for 2012-
2013 were 436.9, 312.6, and 230.1 cm plant-1, from highest
to lowest, for ‘Corona’, ‘Liberty’, and ‘Legacy’ (p < 0.05),
respectively (Table 2). For N sources, LM and CF treatments
had the highest values for this parameter (p < 0.05) with mean
values of 420.5 and 449.5 cm plant-1, respectively. Values
showed nonsignicant differences (p > 0.05) and were only
higher than those obtained for C, CM, and S (p < 0.05) with
242.8, 225.8, and 198.3 cm plant-1, respectively (Table 3).
For the number of basal shoots per plant in the 2013-2014
season, ‘Liberty’ and ‘Legacy’ recorded the highest values
(6.4 and 5.5, respectively). Values showed nonsignicant
differences among them (p > 0.05) and were higher than the
value for ‘Corona’ (p < 0.05) that reached 3.0 (Table 2). The
highest value for N sources (Table 3) was obtained using
F (6.5). This value was signicantly higher (p < 0.05) than
the values for CF, PG, and C, which showed no differences
among them (p > 0.05).
For the sum of lengths of basal shoots during the 2013-
2014 season, the highest values were observed in ‘Liberty’
and ‘Legacy’ (p < 0.05). There was no difference between
these values (p > 0.05) of 337.8 and 306.9 cm plant-1,
respectively. ‘Corona’ had a lower value (p < 0.05) of 196.9
cm plant-1 (Table 2). Treatments LM, F, PL, and BM for N
sources showed the highest values for the sum of lengths of
basal shoots of 416.3, 388.7, 348.3, and 308.3 cm plant-1,
respectively (Table 3). Only the values for LM and F were
higher than those for the other evaluated treatments (p < 0.05).
There was a similarity between PL and C, CF, and S (p > 0.05)
while BM was similar to C, CO, S, CF, and PG (p > 0.05).
When comparing cultivars, the number of lateral shoots
per plant in the 2012-2014 season ranged from 35.1 to 59.3.
The highest value was obtained for ‘Corona’ (p < 0.05)
followed by ‘Liberty’ and ‘Legacy’ without any differences
between them (p > 0.05) (Table 2). Values for N sources
2012-2013 Season
Corona 3.5b 129.5b 34.6a 436.9a 50.3a
Legacy 3.8b 167.2a 12.4c 230.1c 47.0b
Liberty 4.6a 184.8a 17.9b 312.6b 39.7c
2013-2014 Season
Corona 3.0b 196.9b 59.3a 732.8a Nd
Legacy 5.5a 306.9a 35.1b 477.6b Nd
Liberty 6.4a 337.8a 37.0b 433.3b Nd
Table 2. Vegetative and nutritional growth parameters of ‘Corona’, ‘Legacy’, and ‘Liberty’ blueberries in the 2012-2013 and 2013-
2014 seasons.
Different letters in the columns for the same season indicate differences among cultivars according to Tukey’s test (p < 0.05).
Nd: Not determined; nr: number.
Cultivar
Basal shoots
per plant Sum of length
of basal shoots
nr plant-1 cm plant-1
Lateral shoots
per plant Sum of length
of lateral shoots
nr plant-1 cm plant-1
SPAD units
(December)
Units
2012-2013 Season
C 3.3a 130.1b 19.0ab 242.8bc 37.4de
CM 4.0a 158.4ab 17.7ab 225.8bc 34.8e
F 4.6a 178.8ab 24.2a 354.1ab 45.9bc
PG 3.6a 135.9b 23.1a 310.8abc 50.1ab
PL 4.3a 160.0ab 24.6a 373.3ab 43.7c
S 4.1a 171.3ab 11.0b 198.3c 40.6cd
BM 4.2a 154.0ab 24.8a 363.7ab 51.3ab
LM 4.6a 218.3a 24.2a 420.5a 52.2a
CF 3.3a 137.5b 26.3a 449.5a 54.2a
2013-2014 Season
C 3.8d 186.0c 29.8c 311.2cd Nd
CM 4.4abcd 226.5bc 26.3c 337.1cd Nd
F 6.5a 388.7a 48.4abc 661.7abc Nd
PG 4.0cd 198.4c 38.4bc 416.0cd Nd
PL 6.0abc 348.3ab 49.3abc 591.1bcd Nd
S 4.8abcd 222.0bc 24.3c 256.1d Nd
BM 4.8abcd 308.3abc 61.0ab 782.2ab Nd
LM 6.2ab 416.3a 71.1a 1023.8a Nd
CF 4.3bcd 230.4bc 45.8abc 552.4bcd Nd
Table 3. Parameters of vegetative and nutritional growth according to the different N treatments used in the 2012-2013 and 2013-
2014 seasons.
Different letters in the columns for the same season indicate differences between N fertilization treatments according to Tukey’s test (p < 0.05).
Nd: Not determined; nr: number.
Treatment
Basal shoots
per plant Sum of length
of basal shoots
nr plant-1 cm plant-1
Lateral shoots
per pla Sum of length
of lateral shoots
nr plant-1 cm plant-1
SPAD units
(December)
Units
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CHILEAN JOURNAL OF AGRICULTURAL RESEARCH 76(2) APRIL-JUNE 2016
ranged from 24.3 to 71.1 (Table 3). The highest values
were obtained when using LM, BM, PL, F, and CF and
with nonsignicant differences between them (p > 0.05).
Nevertheless, only the LM application resulted in higher
values than those obtained for PG, S, CO, and C (p < 0.05).
Similarly, BM had higher values than those obtained for S,
CM, and C (p < 0.05) (Table 3).
For the sum of lengths of lateral shoots in the 2013-2014
season, the highest value was obtained for ‘Corona’ (p <
0.05) with 732.8 cm plant-1, while values for ‘Legacy’ and
‘Liberty’ had nonsignicant differences between them (p
> 0.05) and were 477.6 and 433.3 cm plant-1, respectively
(Table 2). As for N sources, the LM, BM, and F treatments
showed the highest values for the sum of the lengths
of lateral shoots (Table 3). There were nonsignicant
differences between these values (p > 0.05) of 1023.8, 782.7,
and 661.7 cm plant-1, respectively. Only the values for LM
were signicantly higher than those obtained with the other
evaluated treatments (p < 0.05). Blood meal was signicantly
higher than C, CO, PG, and S (p < 0.05) while F was only
signicantly higher than S (p > 0.05) (Table 3).
There were differences between cultivars for SPAD units.
Values of 50.3, 47.0, and 39.7, from highest to lowest, were
for ‘Corona’, ‘Legacy’, and ‘Liberty’ (p < 0.05), respectively
(Table 2). For N sources, the highest values were obtained for
CF, LM, BM, and PG. Values did not show any signicant
differences (p > 0.05); these were 54.2, 52.2, 51.3, and 50.1,
respectively (Table 3). For CF and LM, values were higher
than for C, CM, F, PL, and S (p < 0.05) while those for BM
and PG were signicantly higher than the results obtained
for C, CO, PL, and S (p < 0.05) (Table 3).
Leaf DM production prior to leaf fall in the three seasons
was generally higher in ‘Corona’ followed by ‘Legacy’ and
‘Liberty’, but nonsignicant differences were found between
cultivars (p > 0.05) (Figures 1a, 1c, and 1e). Recorded
values were 15.96, 7.10, and 6.65 g plant-1 in the 2011-2012
season; 25.76, 18.46, and 14.83 g plant-1 in the 2012-2013
season; 102.56, 65.66, and 31.64 g plant-1 in the 2013-2014
season for ‘Corona’, ‘Legacy’, and ‘Liberty’, respectively
(Figures 1a, 1c, and 1e). For the 2011-2012 season, values
ranged from 3.48 to 12.66 g plant-1 while the highest leaf
DM production was observed using F, CM, PG, PL, BM,
and CF, which was only higher than the value obtained for
S (p < 0.05) (Figure 1b). For the 2012-2013 season, values
ranged from 14.84 to 26.91 g plant-1 while the highest leaf
DM production was obtained using LM. This value was
higher than those obtained for C, CM, F, S, and BM (p <
0.05) (Figure 1d). For the 2013-2014 season, values ranged
from 28.15 to 121.20 g plant-1 while the highest leaf DM
production was also obtained using LM, which was only
higher than values obtained for C, CM, PG, PL, S, and CF (p
< 0.05) (Figure 1f).
Leaf N concentration prior to leaf fall showed differences
between seasons for each evaluated cultivar associated with
the interaction between sources of variation (Table 1 and
Figures 2a, 2c, and 2e). Values for this parameter ranged
from 15.57 to 16.61 g kg-1 in the 2011-2012 season and
showed nonsignicant differences (p > 0.05) (Figure 2a).
For the 2012-2013 season, values ranged from 12.60 to
17.64 g kg-1 with the highest value recorded for ‘Corona’
(p < 0.05) and with no differences between ‘Legacy’ and
‘Liberty’ (p > 0.05) (Figure 2c). For the 2013-2014 season,
leaf N concentration ranged from 6.26 to 11.26 g kg-1. In
this case, values from the highest to the lowest, were for
‘Corona’, ‘Legacy’, and ‘Liberty’ (p < 0.05), respectively
(Figure 2e). Results for the effects of N sources showed
differences between seasons, which were associated with the
interaction between sources of variation (Table 1, Figures
2b, 2d, and 2f). For the 2011-2012 season, values ranged
from 10.68 to 20.26 g kg-1. The highest N concentration was
achieved for CF, which was only higher than values obtained
for C, CM, F, S, BM, and LM (p < 0.05) (Figure 2b). For
the 2012-2013 season, values ranged from 8.44 to 20.88 g
kg-1 and the highest leaf N concentration was achieved using
PL, which was only higher than the values obtained for C,
CM, F, S, BM, FL, and CF (p < 0.05) (Figure 2d). For the
2013-2014 season, values ranged from 6.11 to 12.40 g kg-1
and the highest leaf N concentration was achieved using CF,
F, and PG, which was only signicantly higher than values
obtained for C, CM, PL, and S (p < 0.05) (Figure 2f).
When evaluating each cultivar, N extraction prior to leaf
fall showed differences between seasons associated with the
interaction between sources of variation (Table 1 and Figures
3a, 3c, and 3e). For the 2011-2012 season, leaf N extraction
values varied between 100 and 260 mg plant-1 and the highest
value was obtained for ‘Corona’ (p < 0.05). No differences
were found between ‘Legacy’ and ‘Liberty’ (p > 0.05) (Figure
3a). For the 2012-2013 season, leaf N extraction was between
200 and 450 mg plant-1 and the highest to lowest values were
for ‘Corona’, ‘Legacy’, and ‘Liberty’ (p < 0.05), respectively
(Figure 3c). For the 2013-2014 season, this parameter varied
between 200 and 1370 mg plant-1 while the highest to lowest
values were for ‘Corona’, ‘Legacy’, and ‘Liberty’ (p < 0.05),
respectively (Figure 3e). The effects of N sources showed
differences between seasons (Table 1, Figures 3b, 3d, and
3f). For the 2011-2012 season, values were between 60 and
240 mg plant-1 and the highest N extraction was achieved
using PL, F, PG, and CF, which was only higher than the
values obtained for C, CM, and S (p < 0.05) (Figure 3b).
For the 2012-2013 season, values were between 130 and 450
mg plant-1 the same as for the 2011-2012 season when the
highest leaf N extraction was achieved using PL, F, PG, and
CF, which only exceeded the values obtained for C, CM, and
S (p < 0.05) (Figure 3d). For the season 2013-2014, values
varied between 150 and 1400 mg plant-1 and the highest leaf
N extraction was obtained using LM and F, which was only
higher than the values obtained for C, CM, PG, PL, and S (p
< 0.05) (Figure 3f).
Fruit production in the 2013-2014 season (rst crop
production season) ranged from 128.29 to 264.92 g plant-1
(Figure 4); the highest yield was obtained for ‘Corona’ (p
< 0.05) followed by ‘Legacy’ and ‘Liberty’; there were
no differences between them (p > 0.05). The effects of N
sources on fruit yield (Table 1, Figures 4b) resulted in values
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that ranged from 104.25 to 341.54 g plant-1; the highest yield
was achieved using F and LM, which was only higher than
the values obtained for C, CM, PG, S, and BM (p < 0.05)
(Figure 4b). Mean fruit weight in the 2013-2014 season
ranged from 1.56 to 2.63 g (Figures 4c and 4d); the highest
weight was obtained in ‘Corona’ followed by ‘Legacy’ and
‘Liberty’; there were no differences between them (p >
0.05). No differences were found for this parameter when
comparing N sources, (p > 0.05).
DISCUSSION
The present study focused on the effects of N supply through
different organic sources as related to conventional fertilizers,
as well as in the response of three blueberry cultivars. Effects
of other nutrient supply with the different nutritional sources
were not discussed; there are several reports indicating that
the main nutrient affecting the parameters analyzed in the
present study is N (Tamada, 2004; Bryla and Machado,
2011; Bañados et al., 2012; Retamales and Hancock, 2012).
Vegetative growth of blueberry plants, expressed as the sum
of the lengths of basal and lateral shoots in cm plant-1, was
quantitatively higher in the 2013-2014 season compared to the
2012-2013 season for the three cultivars. The accumulation of
vegetative growth (sum of lengths of basal and lateral shoots)
in the 2012-2013 season in ‘Legacy’ and ‘Liberty’ was 70.0%
and 88.0%, respectively, compared to ‘Corona’ (Table 2). The
accumulation of vegetative growth in ‘Legacy’ and ‘Liberty’
Figure 1. Leaf dry matter (DM) production prior to leaf fall (May) in three consecutive seasons for different blueberry cultivars
(Corona, Legacy, and Liberty) and N fertilization treatments; A) 2011-2012, blueberry cultivars; B) 2011-2012, N fertilization
treatments; C) 2012-2013, blueberry cultivars; D) 2012-2013, N fertilization treatments; E) 2013-2014, blueberry cultivars; F) 2013-
2014, N fertilization treatments.
Treatments: Compost (CM), Purely Grow (PG), Purely Lysine (PL), Fertil (F), blood meal (BM), lupine meal (LM), control treatment with no fertilization (C),
and two conventional treatments with urea (CF) and sodium nitrate (S).
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was 84.0% and 83.0%, respectively, compared to ‘Corona’ for
the 2013-2014 season (Table 2). At the same time, the increase
in vegetative growth for each cultivar between the 2012-2013
and 2013-2014 seasons was 64.0%, 97.0%, and 55.0% for
‘Corona’, ‘Legacy’, and ‘Liberty’, respectively. There were
quantitative differences between cultivars for the sum of the
number of lateral and basal shoots (Table 2). The sum of the
number of shoots in the 2012-2013 season for ‘Legacy’ and
‘Liberty’ was 42.5% and 59.1%, respectively, compared to
‘Corona’, and values were 65.2% and 69.7% for ‘Legacy’ and
‘Liberty’, respectively, compared to ‘Corona’ for the 2013-2014
season. At the same time, the increase in the sum of the number
of lateral and basal shoots in each cultivar between the 2012-
2013 and 2013-2014 seasons was 63.5%, 150.6%, and 92.9%
for ‘Corona’, ‘Legacy’, and ‘Liberty’, respectively. These
differences are explained by the vigor conditions described
for the three evaluated cultivars (San Martín, 2013). A higher
difference between cultivars was found for the sum of the
number of lateral and basal shoots, which could be associated
with a compensation effect between both the number and
length of shoots: moreover, the difference between cultivars, as
a percentage, was lower for the sum of the lengths of the basal
and lateral shoots. ‘Corona’ is one of the new cultivars on the
market; it is an early-season cultivar with high productivity. On
the other hand, ‘Liberty’ is a mid-to-late season cultivar which
depends on the agro-climatic zone where the plants are grown,
and it has relatively vigorous growth. ‘Legacy’ is a mid-season
cultivar with vertical and vigorous growth.
Figure 2. Leaf N concentration in three consecutive seasons for different evaluated blueberry cultivars (Corona, Legacy, and
Liberty) and N fertilization treatment used; A) 2011-2012, blueberry cultivars; B) 2011-2012, N fertilization treatments; C) 2012-
2013, blueberry cultivars; D) 2012-2013, N fertilization treatments; E) 2013-2014, blueberry cultivars; F) 2013-2014, N fertilization
treatments.
Treatments: Compost (CM), Purely Grow (PG), Purely Lysine (PL), Fertil (F), blood meal (BM), lupine meal (LM), control treatment with no fertilization (C),
and two conventional treatments with urea (CF) and sodium nitrate (S).
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‘Liberty’ also has a later ripening season compared to
the other cultivars under study. Therefore, it has lower N
uptake in the postharvest period (Larco et al., 2013). It
is important to note that optimal timing for applying N
fertilizer is determined by the uptake pattern of the fruit
in each phenological stage (Bañados et al., 2012), and
most of the uptake occurs between sprouting and veraison
(Hanson, 2006; Bañados, 2006). In the case of blueberries,
each cultivar has an individual N consumption pattern,
which could explain interactions between cultivars and
N sources obtained in each season, as well as differences
in their response to both cultivar and N source between
seasons. The different effects of N sources between seasons
(Table 1, Figures 1b, 1d, and 1f) could be associated with
the behavior of both the vegetative and reproductive
development of each cultivar, and vegetative development
depends on N availability (Bryla and Machado, 2011). The
sandy loam used could generate loss by lixiviation of fast
release N sources, so the sources of medium release, such as
LM, could generate a higher adjustment between N uptake
and supply.
The N source with the best result for vegetative
growth was LM, whose effect was previously explained.
In contrast, the control without N had the lowest values,
and the lack of N limited the synthesis of proteins,
nucleic acids, phospholipids, and a number of secondary
metabolites (Miller and Cramer, 2004), which affected
vegetative development and the next reproductive stage.
The application of N sources from different origins
and composition promotes the growth of benecial
Figure 3. Nitrogen extraction in three consecutive seasons for different blueberry cultivars (Corona, Legacy, and Liberty) and N
fertilization treatments; A) 2011-2012, blueberry cultivars; B) 2011-2012, N fertilization treatments; C) 2012-2013, blueberry
cultivars; D) 2012-2013, N fertilization treatments; E) 2013-2014, blueberry cultivars; F) 2013-2014, N fertilization treatments.
Treatments: Compost (CM), Purely Grow (PG), Purely Lysine (PL), Fertil (F), blood meal (BM), lupine meal (LM), control treatment with no fertilization (C),
and two conventional treatments with urea (CF) and sodium nitrate (S).
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Figure 4. Fruit production and fruit weight for the December 2013-February 2014 harvest; A) Production per plant for the different
blueberry cultivars (Corona, Legacy, and Liberty); B) production per plant for N fertilization treatments; C) fruit weight for different
cultivars; D) fruit weight for N fertilization treatments.
Treatments: Compost (CM), Purely Grow (PG), Purely Lysine (PL), Fertil (F), blood meal (BM), lupine meal (LM), control treatment with no fertilization (C),
and two conventional treatments with urea (CF) and sodium nitrate (S).
soil microorganisms associated with the root system of
blueberries, higher uptake capacity, and essential nutrient
concentration (Ruan et al., 2010). Treatment S (N as sodium
nitrate) had a negative effect on the blueberries, which is
explained by fast Na release in the sandy loam soil that
produces toxicity in blueberries (Bryla and Machado, 2011;
Bañados et al., 2012). Therefore, reduced vegetative growth
and lower DM production were expected, as observed in
the three evaluated cultivars; values were below or similar
to the control treatment. Based on N contribution, fast
release treatments of N such as PG and FC could have had
greater shoot growth; however, these treatments could have
had higher N loss through leaching (Hirzel, 2014), which is
an effect not determined in the present study.
Leaf DM production in the three cultivars was higher in
‘Corona’ during the three seasons and proportionally higher
in the rst season (Figure 1A); it is associated with the initial
vigor described for this cultivar (San Martín, 2013). The
higher leaf DM production in ‘Corona’ in this experiment
is explained by the increased accumulation of reserves in an
aging plant, which results in higher leaf mass and roots, and
therefore has greater primary and secondary productivity
(Budeguer et al., 2011). In the last two evaluated seasons,
the highest levels of leaf DM were obtained with treatments
based on meals (BM and LM) in the three cultivars under
study (Figure 1), as well as the F treatment. These fertilizers
decompose very easily and are associated with its C:N ratio,
low molecular weight compounds, and high presence of
amino acids with a low C:N ratio (Fuller, 2004). In fact, some
authors have reported that there may be 50% decomposition
30 d after the application, so that N is readily available to
plants and can be easily released (Müller and von Fragstein,
2006; Hirzel, 2014).
The leaf N concentration interactions for the 2013-2014
season (Figure 2) can be explained by the differences in
leaf mass and N uptake period of each cultivar (Bañados et
al., 2012), which in turn are associated with the dynamic N
release of each source used (Hirzel, 2014). ‘Corona’ was the
cultivar that accumulated the highest leaf N content followed
by ‘Legacy’ (Figure 2). Both ‘Corona’ and ‘Legacy’ are
considered as vigorous cultivars with early- and mid-season
fruiting (longer postharvest period to accumulate reserves
that promote vegetative growth in the following season).
These results are consistent with those reported by Miller
et al. (2006), who compared the uptake and accumulation
of macronutrients in 2-yr-old blueberry plants under organic
and conventional farming. This study showed that organically
grown plants had lower N and P leaf concentration than
plants treated with conventional fertilizers. Leaf symptoms
were also evidenced in this study and the researchers
determined that supplying effective nutrient rates with
organic fertilizers is more difcult. In addition, Bañados
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et al. (2012) has indicated that when these nutrients are
more available, uptake is quicker and improves tissue
concentration the same as conventional fertilizers do. Leaf N
uptake prior to leaf fall (Figures 3A, C, and F) is an indicator
of N recovery capacity, which exhibited the same behavior
as leaf DM production (Figures 1A, C, and F); this effect
was previously discussed. The effect of leaf N concentration
prior to leaf fall is quantitatively lower for N extraction
(Figures 2A, C, and F). Accumulated leaf N uptake during
the three evaluated seasons with each fertilization treatment
was 1.87 (LM), 1.71 (F), 1.60 (BM), 1.59 (CF), 1.44 (PG),
1.30 (PL), 0.46 (C), 0.46 (CM), and 0.46 (S) g pl-1 with an
accumulated rate of 56 g N plant-1 in the three seasons of
the experiment. These uptake values were much lower than
those reported by Bañados et al. (2012) for the leaves of the
cultivar ‘Bluecrop’ collected prior to leaf fall (October in
the Northern Hemisphere) for a 2-yr experiment in Oregon
in a ne loamy soil fertilized with ammonium sulfate. This
lower N recovery could be associated with the soil used in
the present experiment because of the higher risk of losses
by lixiviation and lower N availability of the fertilizers used.
The time of leaf sampling in the present experiment was May
(November in the Northern Hemisphere). This difference of
one month between both sampling dates could also explain
the lower N recovery associated with higher N translocation
to other plant structures prior to leaf fall.
For N extraction by different blueberry cultivars during
the growing season, authors such as Bañados (2006), Gale
et al. (2006), and Hanson (2006) have indicated that N
fertilizers should be applied at different rates depending on
the cultivar. This coincides with the ndings of the present
study because ‘Liberty’ had lower levels of leaf N extraction
compared to ‘Corona’ and ‘Legacy’.
Measurements of mean fruit weight and yield per plant
were affected by the interaction between cultivars and
evaluated N sources. This interaction is associated with
differences in the vigor of each cultivar. Other studies
have reported that ‘Legacy’ showed lower photosynthesis
than ‘Bluegold’ in the absence of N (Yañez-Mansilla et al.,
2014). In blackberries, the cultivar plays a key role in the
N source and N application rate (Fernández-Salvador et
al., 2015). The effect of seasonality on N uptake, which is
related to fruit earliness, is also associated with the speed of
N release. ‘Corona’ had a higher mean fruit weight of 2.64
g fruit-1, which was within the range of values described for
this cultivar (Lobos et al., 2011). ‘Legacy’ and ‘Liberty’ had
mean weights of 1.78 and 1.56 g fruit-1, respectively. These
values were lower than those obtained for ‘Corona’, but they
were also within the range of values for this cultivar (Serri
and Hepp, 2006; Retamales et al., 2014). The N sources
that were used did not generate any signicant differences
on these parameters. However, fruit weight was higher
when using LM, CF, and F in variable g fruit-1 (Figure 4D).
Treatments that had the lowest mean fruit weight values of
were S, CM, and C (Figure 4D). This effect can be attributed
to the reduced availability of N in treatments C and CM and
also to the negative effect of using S in this sandy soil; N
availability, especially at the beginning of vegetative growth,
is closely related to the productivity of blueberry plants
(Stadler et al., 2006). Fruit yield per plant is also associated
with the pruning operations conducted in the preceding
winter season, which consisted in leaving ower buds in
accordance with the vegetative development of the plant.
Thus, weaker plants or those with fewer shoots were pruned
more severely than vigorous plants in order to stimulate
growth, yield, and fruit quality in the long term (Williamson
et al., 2004).
CONCLUSIONS
Vegetative growth of evaluated blueberry plants has
an effect on the cultivar, and it is also affected by the N
source used. ‘Corona’ had higher vegetative growth than
‘Legacy’, which in turn was higher than ‘Liberty’. Quick-
release N sources, such as urea, Purely Grow, and Purely
Lysine, generated higher vegetative growth in ‘Legacy’,
while the use of lupine meal generated a higher growth
rate in ‘Corona’ and ‘Liberty’.
Leaf N accumulation prior to leaf fall showed differences
between cultivars, seasons, or plant development stage and
had effects depending on the N source used. ‘Corona’ had
the highest accumulation, while the N sources that achieved
the highest accumulation were urea and Purely Lysine in the
rst two seasons and urea, Fertil, and Purely Grow in the last
season. As the plants aged, lower leaf N accumulation was
observed.
Fruit production varied depending on the cultivar and N
source used. The highest yield was observed in ‘Corona’
followed by ‘Legacy’ and ‘Liberty’. The N sources that
achieved the highest fruit yield were lupine meal and
Fertil. Fruit weight only depended on the cultivar and
the highest values were obtained in ‘Corona’ followed
by ‘Legacy’ and ‘Liberty’, and they were not affected
by the N source used. Leaf chlorophyll content showed
differences between cultivars and N sources. ‘Corona’ had
the highest values followed by ‘Legacy’ while ‘Liberty’
reached lower values. The N sources that achieved the
highest leaf chlorophyll content were urea, lupine meal,
blood meal, and Purely Grow.
Finally, under the conditions of this experiment, lupine
meal obtained the highest values for most of the evaluated
parameters. As for the cultivar, ‘Corona’ had the highest
values for these parameters. These results suggest that future
experiments about organic fertilization in blueberry must
include combinations of different N sources and consider
fast, medium, and slow N supply rates.
ACKNOWLEDGEMENTS
The authors would like to thank the Foundation for
Agricultural Innovation (FIA) through project PYT-2011-
0064 and the Chilean company ‘Hortifrut Chile S.A’ for their
nancial support.
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