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Communications in Soil Science and Plant Analysis
ISSN: 0010-3624 (Print) 1532-2416 (Online) Journal homepage: http://www.tandfonline.com/loi/lcss20
Assessment of Compost Extract on Yield and
Phytochemical Contents of Pak Choi (Brassica rapa
cv. chinensis) Grown under Different Fertilizer
Strategies
Abd Rahman Jabir Mohd Din, Kian Kai Cheng & Mohamad Roji Sarmidi
To cite this article: Abd Rahman Jabir Mohd Din, Kian Kai Cheng & Mohamad Roji Sarmidi (2017)
Assessment of Compost Extract on Yield and Phytochemical Contents of Pak Choi (Brassica rapa
cv. chinensis) Grown under Different Fertilizer Strategies, Communications in Soil Science and
Plant Analysis, 48:3, 274-284, DOI: 10.1080/00103624.2016.1269793
To link to this article: http://dx.doi.org/10.1080/00103624.2016.1269793
Accepted author version posted online: 06
Jan 2017.
Published online: 06 Jan 2017.
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Assessment of Compost Extract on Yield and Phytochemical
Contents of Pak Choi (Brassica rapa cv. chinensis) Grown under
Different Fertilizer Strategies
Abd Rahman Jabir Mohd Din
a
, Kian Kai Cheng
b
, and Mohamad Roji Sarmidi
a,c
a
Innovation Center in Agritechnology for Advanced Bioprocessing, Universiti Teknologi Malaysia, Johor Bahru,
Malaysia;
b
Department of Bioprocess Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia,
Johor Bahru, Malaysia;
c
Institute of Bioproduct Development, Universiti Teknologi Malaysia, Johor Bahru, Malaysia
ABSTRACT
An experiment was conducted to assess the effect of different extraction of
compost extracts on pak choi (Brassica rapa cv. chinensis) under two fertilizer
regimes. Aerated compost extract (ACE) and non-aerated compost extract (NCE)
were prepared and all treatments (ACE + organic fertilizer, NCE + organic ferti-
lizer, ACE + inorganic fertilizer, NCE + inorganic fertilizer) were conducted in
randomized block design. Soil microbiological analysis after treatment was done.
PlantsgrownwithACE+inorganicfertilizers yielded maximum in fresh, dry
weight, and N mineral content compared to others. Plants receiving
NCE + organic fertilizers produced a higher phenolic content, whereas antiox-
idant capacity was observed maximum at NCE + inorganic fertilizers. Soil micro-
biological analysis significantly increased in yeast and nitrogen fixing bacteria
count at ACE + organic fertilizers. The co-application of inorganic fertilizers and
compostextracthadasignificanteffecton vegetative growth, quality of the pak
choi, and soil fertility.
ARTICLE HISTORY
Received 23 November 2015
Accepted 26 October 2016
KEYWORDS
Compost extract; pak choi;
fertilizer strategies;
microbiological analysis;
phytochemicals
Introduction
Compost extract has been widely used to enhance plant yield and improve microbial communities
present in the soil and the mineral nutrient quality of the plants. Compost extracts contained a lot of
beneficial microorganisms which is reported to enhance plant growth by promoting soil fertility and
improving the mineral concentration in plant tissue (Fritz et al. 2012). Compost extract or known as
compost tea is a fermented compost aqueous solution arising as a result of incubation of composted
materials with or without the microbial food additives within certain period of incubation time (Koné
et al. 2010). Besides, the use of compost extract was becoming an attractive disease management option to
suppress a range of plant diseases when applied as foliar sprays or soil drenches (Pane, Celano, and
Zaccardelli 2014; Scheuerell and Mahaffee 2006). It has been reported that compost extracts obtained
vermicompost are able to enhance the growth, mineral nutrient, and the yield of leafy vegetables when
applied as soil drench biweekly (Pant et al. 2009). It is most likely the interaction of several components
such as mineral nutrient, phytohormones, as well as living microbial metabolites within compost
extracts, that contributes to the plant growth enhancement.
Vegetables are becoming an ideal food for human consumption, especially for those who are concerned
on healthy food intake. Pak choi (Brassica rapa cv. chinensis) is a popular cultivated leafy, cruciferous, and
succulent vegetables, grown in areas under moderate temperature and rainfall distribution. In Malaysia, the
total planted area of pak choi in 2011 was 8310 ha and 120,160 metric tons were produced with the average
yield amounting MYR 350 million. Pak choi has a short life cycle, enabling this leafy vegetable to be
CONTACT Abd Rahman Jabir Mohd Din jabir@ibd.utm.my Innovation Center in Agritechnology for Advanced
Bioprocessing, Universiti Teknologi Malaysia, Johor Bahru, Malaysia.
© 2017 Taylor & Francis
COMMUNICATIONS IN SOIL SCIENCE AND PLANT ANALYSIS
2017, VOL. 48, NO. 3, 274–284
http://dx.doi.org/10.1080/00103624.2016.1269793
harvested within a month of cultivation. Pak choi is good choice of daily food intake as it offers broad
spectrum natural phytochemical compounds such as carotenoids, tocopherols, phenolics, selenium,
glucosinolates, and ascorbic acids (Cartea et al. 2011). This leafy vegetable is said possess relatively abundant
sources of antioxidant when biofertilizers were applied (Yee et al. 2007).Basedonthis,reviewsonthe
phytochemical compounds of vegetables show significant differences based on climatic season, genotype,
and agronomic practices. Young et al. (2005) studied that pak choi grown organically had higher
concentration of total phenolics than grown conventionally. It is said that major phytochemical com-
pounds identified in pak choi were kaempferol derivatives, hydroxycinnamoylmalic acis, and hydroxyl-
cinnamoylquinic acids (Lin and Harnly 2010). Likewise, because of its health-promoting effects, the
bioavailability of phytochemical compounds would allow to clarify better on fertilizer management
specifically over the plant and ultimately regulation of the biosynthesis of secondary metabolites to attain
high levels of nutritionally important macro- and micronutrients. Nowadays, agricultural system practices
are highly concerned to shift to new paradigm in using biofertilizers or any organic source nutrient
supplements in obtaining the best quality of yields. It is believed that the use of compost extract will give a
positive effect on plant growth and increase bioactive compounds’bioavailability. Keeping on view of that,
several investigations were done to ascertain the conjunctive effect of both inorganic fertilizers with
compost tea to stimulate crop yield by improving efficiency of nutrient mobilization and reduce the
environmental risks (Mahmoud, El-Gizawy, and Geries 2015;Siddiquietal.2011). Integrating nutrient
management between organic materials and inorganic constituents is the best option for nutrient mobi-
lization and becoming a current trend to be recognized to meet the requirements of different crop varieties
and cultivation systems. In addition, increasing attention among consumers has been paid to the intake of
plant products, associated with good bioactive compounds grown under sustainable cultivation system
which was believed having the potential in reducing the risk of getting chronic diseases. Several studies have
shown benefits from the use of compost extracts as organic materials and inorganic substrate constituents
to improve productivity of crop yields. It has been reported that application of aerated compost extracts
(ACE) and biofertilizers (Azotobacter chroococcum and Azospirillum brasilense) plus with mineral nitrogen
level of 286 kg N ha
−1
level significantly increased bulb and plant dry weight of onion at 120 days after
transplanting (Mahmoud, El-Gizawy, and Geries 2015). Hargreaves, Adl, and Warman (2009)concluded
that non-aerated compost extract (NCE) from municipal solid waste and inorganic fertilizers significantly
improved concentration of macronutrients of strawberry. Sanwal et al. (2006) found that the combination
use of NCE and compost deliberately increased crop yield and dietary antioxidants of broccoli. An
increment in tomato yield and lycopene content was observed with the conjunctive use of compost and
half strength of inorganic fertilizers (Verma et al. 2015).
Although considerable research related to the nutrient management option of compost extract has
been conducted, their efficacy still remains variable among different compost batches and mineral
fertilizers used (Scheuerell and Mahaffee 2006; Sharma and Banik 2014). However, further insights are
necessary to confirm on action mechanisms linked to explain interaction of compost extract and mineral
fertilizers on the improvement of crop yields and suppressiveness mechanism against crop pathogens.
Numerous experiments have mentioned the use of compost extracts which help to enhance plant health
quality, yield, and nutritional traits (El-Gizawy, Shalaby, and Mahmoud 2014; Kim et al. 2015; Pant et al.
2011; Siddiqui et al. 2009). Thus, the results are relatively different depending on the type of compost
used, compost maturity, period of compost extract extraction, type of crops, microbial additives, and
parameters used to access the potential of compost extract. All these factors could stimulate the change to
the chemical, physiological, and biological system of the plant and soil structures as a whole. Pant et al.
(2012) conclusively reviewed the quality of compost extracts originated from wide range of composted
materials for pak choi growth. In addition, Siddiqui et al. (2009) also reported the use of compost extract
from agro waste for disease suppression on okra.
Given the mounting data in support the role of relationship between mineral fertilizers and compost
extracts in improving pak choi productivity under Malaysia tropical climate, explanation on this would
be extreme benefit to public. Better understanding of the relationship of fertilizer and nutrient mobiliza-
tion between of these two factors would improve on how to cultivate this cruciferous crop.
COMMUNICATIONS IN SOIL SCIENCE AND PLANT ANALYSIS 275
Although many reports have demonstrated the beneficial effect of compost extracts, the influence on its
phenolic content and antioxidant properties is still lacking. Therefore, there is an urgency to study the
influence of compost extracts and different fertilizers regimes application on the yield production, soil
fertility in conjunction with microbial population profiles, and the phytochemical compounds of pak
choi under tropical climate in Malaysia. Furthermore, the present study will help to elucidate the main
factor underlying interaction mechanism among parameters leading to improve pak choi yields.
Material and methods
The experiment was conducted in completely randomized design comprising of 4 treatments with 10
replications for each treatment from January to March 2015. Two different treatments (organic and
inorganic) were applied to the plants with two extraction methods of compost tea. Five seeds of pak choi
(B. rapa cv. chinensis group) were grown in a mixture of soil compositions (black soil, peat moss, sand at
3:2:1 v/v). After 2 weeks, the plants were thinned to one plant each (30 cm × 25 cm) pots. The plants were
grown and watered twice a day to maintain the soil moisture. Both organic (Chicken Organic Fertilizer
5-3-2, YMWOO Cooperation Sdn Bhd) and inorganic fertilizers (nitrogen, phosphorus, and potassium
[NPK] Growing Inducer 15-15-15, YMWOO Cooperation Sdn Bhd) were applied to the plants. A total of
150 mg N kg
−1
of the fertilizer was measured to supply the nutrient to the soil for both treatments. The
employment of the compost extract was done weekly at 200 mlpot
−1
for 4 weeks to the root zone after the
transplanting period.
The commercial compost (Serbajadi Multipurpose Compost) from agro waste source was obtained
from local market. The compost extracts were prepared based on two extraction methods which
constituted three treatments: (1) ACE and (2) NCE. Compost extract was prepared by brewing compost
and water at the ratio of 1:10 (w/v; compost: water) in a 10-l plastic tank according to method described
by Naidu et al. (2010). Tap water was aerated for 24 h to dechlorinate the water prior to use. Both extracts
were brewed for 7 days at 27 °C and stirred once on the third day of incubation. ACE was prepared and
an aquarium air pump (AP 005 Xilong Aquarium Pump, HYGEN Aquarium Enterprise, Malaysia) was
used to supply oxygen for resulting ACE. NCE was produced in the same way as ACE without any
aeration supplied. All of the resulting compost extracts were filtered through a double-layered cheese
cloth and kept at 4 °C until further used.
Physiochemical and microbial analysis of compost extracts were performed (Table 1). Two 100 ml
samples of each compost extract were taken for this analysis. The pH and carbon-to-nitrogen (C:N) ratio
were measured by using a pH meter (Delta 320, Mettler Toledo,Germany) in a 1:4 (v/v) deionizedwater/
compost extract. The nitrogen content was measured through the acid combustion elemental analysis
method using micro-Kjeldahl method (Tandon 1993). The mineral content nutrients of the leafy
vegetable parts and soil mixtures including P, K, magnesium (Mg), and calcium (Ca) were measured
by using inductively coupled plasma-optical emission spectrometry (PerkinElmer Model Optima 8300,
USA). The microbial diversity in compost extracts and soil was determined by serial dilution spread
method on media prepared (Table 1). A 10-fold serial dilution of each sample was prepared. Microbial
Table 1. Physiochemical and microbial analysis of compost extracts used.
Parameters ACE NCE
pH 6.86 6.7
N (ppm) 150.00 3020.00
P (ppm) 61.00 72.50
K (ppm) 640.00 872.00
C:N ratio 1.90 0.11
Lactic acid bacteria (cfu ml
−1
) 3.3 × 10
4
1161.0 × 10
4
Total bacteria (cfu ml
−1
) 3.9 × 10
7
8.5 × 10
7
Yeast (cfu ml
−1
) 3.0 × 10
5
88.5 × 10
5
Pseudomonas sp. (cfu ml
−1
) 0.53 × 10
7
2.48 × 10
7
Nitrogen-fixing bacteria (cfu ml
−1
) 1.78 × 10
7
1.85 × 10
7
276 A. R. J. MOHD DIN ET AL.
colonies were enumerated as colony forming units per ml (cfu ml
−1
). Each sample of 10 g was suspended
in 90 ml of sterilized saline and shaken thoroughly. Then, 0.1 ml of each inoculum was inoculated into
MRS agar, chloramphenicol glucose yeast extract agar, nitrogen-free medium (Ashby’s medium),
centrimide agar (Pseudosel medium), nutrient agar for isolation of lactic acid bacteria, yeast, nitrogen
fixing bacteria, Pseudomonas sp., and total bacteria, respectively. The samples were incubated at 30 °C for
5 days (Ashby 1907).
The plants were harvested after 30 days after transplanting. A total of 10 plants per treatment were
washed in running tap water and analyzed according to the recommended procedures for extraction of
phytochemical compounds and nutrient content analysis. Soil samples were taken from plots from each
plot at harvest stage. The samples were stored at 4 °C until microbiological analyses were undertaken.
The leafy parts of vegetable were cut off and analyzed for mineral tissue content (N, P, K, Ca, and Mg).
The fresh weight of the whole plant, shoot length, and root length was recorded. Determination of the
biomass of harvested plant was done and recorded. The plants were dried in an oven at 60 °C for 48 h
until a constant weight was achieved (Oliveira et al. 2015). The plants were stored at 4 °C immediately in
freezer until further analysis.
Total phenolic content (TPC) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) were measured according to
methods described by Parthasarathy et al. (2009) and Azlim Almey et al. (2010)withminormodifications.
The antioxidant content was analyzed by extracting 10 g of leafy part of pak choi with 100 ml of ethanol
(1:10 v/v) and left on a shaker for 72 h at room temperature. Crude extracts were obtained by filtration and
evaporation of the extracts under pressure using a rotary evaporator at 40 °C for 30 min. Stock solutions of
extracts and standard solutions of gallic acid were prepared. Extracts or gallic acid solution was mixed to
diluted Folin–Ciocalteu reagent (FC) and left for 3 min before adding 1.5 ml of sodium carbonate. The TPC
ofvegetableextractswasmeasuredbyreadingtheabsorbanceofthemixture(FCreagentandaqueous
sodium carbonate) at 765 nm using UV–vis spectrophotometer (Ultrospec 3100 pro, Amersham
Biosciences, USA) after 60 min of incubation. TPC was calculated and expressed as milligrams of gallic
acid equivalents (GAE) per gram of extracts. Antioxidant capacity of the extract was measured based on the
DPPH free radical scavenging ability of extracts and the absorbance was read at 517 nm using UV–vis
spectrophotometer (Ultrospec 3100 pro, Amersham Biosciences, USA). Ethanolic solution of DPPH (2 ml)
was added to the extracts (500 μl) and kept in a dark place for 30 min. The extracts were then evaluated
against a standard curve of Trolox. The percentage of inhibition was measured and the total antioxidant
capacity (mg ml
−1
) was measured by using the following formula = (A
0
−A
t
/A
0
) × 100, where A
0
is the
absorbance of control and A
t
istheabsorbanceoftheextract.
Analysis of variance of plant morphological parameters, physiochemical and microbial analysis,
mineral nutrient content, and antioxidant capacity of pak choi were performed on treatments and the
means were separated using DMRT through the SPSS 16.0 statistical software (SPSS Inc., Chicago, IL
USA). Statistical significance was obtained at 95% confidence level (P< 0.05).
Results
The physiochemical properties and microbial analysis of the compost extracts used in this study were
presented in Table 1. The pH was found similar for both compost extracts. Overall, NCE had the highest
quantities of macronutrients and microbial population compared to ACE. Microbial populations in ACE
and NCE were tabulated in Table 1 and within acceptable limits. NCE gave the highest enumeration of
total bacteria, Pseudomonas, lactic acid bacteria, yeast, and nitrogen-fixing bacteria compared to ACE.
The fresh weight and dry weight of pak choi (B. rapa cv. chinensis) were significantly improved with the
combination use of ACE and inorganic fertilizer with 59.89 and 12.27 g, respectively (Table 2). The
lowest (43.12 g) fresh weight of the plant was obtained when the combination treatment of ACE and
organic fertilizer was done. It was noticed that the fresh weight of pak choi was closely similar in pattern
as the dry weight of pak choi itself. A positive result was achieved by applying synergistic treatment of
ACE and inorganic fertilizer, demonstrating an improved result of both fresh and dry weight of pak choi.
A similar pattern was also recorded for the shoots length. The effect of compost extract on the shoots
COMMUNICATIONS IN SOIL SCIENCE AND PLANT ANALYSIS 277
length was not significant (P> 0.05) with the treatment receiving combination application of ACE and
inorganic fertilizer giving the highest value of shoot length (26.50 cm) compared to the other treatments.
The interaction between conjunctive use of compost extracts and mineral nutrient sources on plant shoot
length was not significant difference (P> 0.05). The combination of ACE and inorganic fertilizer had a
greater effect on the root morphological trait (21.00 cm) and was followed closely by the application of
ACE + organic fertilizers. The effect of the maximum root length and their interaction on fresh weight
was correlatively positive receiving the treatment of ACE and inorganic fertilizer. Whereas the lowest
value of root length (11.50 cm) was observed after the application of NCE and organic fertilizer, ACE
with organic fertilizer had a greater effect on the N, Mg, and Ca uptake (Table 3). The total N content per
plant was higher (0.57%) and relatively consistent with the fresh weight of each plant for the compost
extract together with inorganic fertilizer. However, P and K content has conversely increased up to
553.02% and 3105.61%, respectively, for the combination of NCE and inorganic fertilizer, respectively,
over other treatments. NCE application along with inorganic fertilizers produced a general increase in P
and K content in plant tissues and there was significant difference (P< 0.05) between them. On other
sides, ACE application along with organic fertilizers gave a positive impact on P and K contents in pak
choi leaf tissue. N, P, and Ca content were generally at the lowest when treated with NCE together with
organic fertilizer. The values increase for K content (3105.61 mg l
−1
) illustrated the superiority of
integrated application of NCE and inorganic fertilizer. Treatment receiving ACE along with organic
fertilizers showed significantly higher values of Ca content as compared to other treatments. A positive
interaction of organic fertilizers in conjunction with both ACE and NCE demonstrated the maximum
Mg content by 239.71 and 235.12 mg l
−1
,respectively.
Nutrient sources treatment produced the different concentrations of TPC and antioxidant capacity
within pak choi extracts (Table 4). These two bioactive compounds in pak choi were measured at
maturity stage. The TPC for all of the treatments showed insignificant difference (P> 0.05). Plants
receiving NCE along with organic fertilizers produced a higher phenolic content (829.29 mg GAE g
−1
)
when compared to others. Followed by the integrated application of ACE + organic fertilizers
(825.93 mg GAE g
−1
), the lowest content (824.12 mg GAE g
−1
) was recorded by treatment of ACE
along with inorganic fertilizers. Furthermore, the effect of NCE recorded good TPC among the organic
and inorganic fertilizers approach. There is a significant difference (P< 0.05) between the plant treated
with ACE and NCE under organic fertilizer between antioxidant activities of the samples (Table 4). The
effect of compost extract on phytochemicals specifically the phenolic content of all of the plants was
generally similar. The maximum concentration of antioxidant compounds (1164.85 mg ml
−1
)was
observed in pak choi leaves extract receiving the conjunctive nutrient treatment of NCE and inorganic
fertilizer. However, no significant difference (P> 0.05) in antioxidant capacity was recorded among the
plant treated with NCE + organic fertilizers and ACE, NCE + inorganic fertilizers. Except for ACE along
with organic fertilizers, low antioxidant capacity was significantly observed than others. In general,
Table 2. Effect of use of compost extract and fertilizer treatment on plant morphological traits.
Treatment Fresh weight (g) Dry weight (g) Shoot length (cm) Root length (cm)
Organic + ACE 43.12
a
10.39
a
24.50
a
17.50
ab
Organic + NCE 55.08
a
10.81
a
25.00
a
12.50
a
Inorganic + ACE 59.89
b
12.27
b
26.50
a
21.00
b
Inorganic + NCE 48.10
a
10.59
a
25.50
a
11.50
a
Means with the same letters within a column are not significantly different at P< 0.05.
Table 3. Effect of conjunctive use of nutrient sources on mineral nutrient content in pak choi leaves.
Treatment N (mg L
−1
) P (mg L
−1
) K (mg L
−1
) Mg (mg L
−1
) Ca (mg L
−1
)
Organic + ACE 0.53
bc
501.47
b
2862.39
b
239.71
a
1489.06
b
Organic + NCE 0.22
a
456.39
a
2666.17
a
235.12
a
1302.98
a
Inorganic + ACE 0.57
c
488.25
ab
2642.00
a
201.10
a
1328.00
a
Inorganic + NCE 0.36
ab
553.02
c
3105.61
c
234.84
a
1427.86
b
Means with the same letters within a column are not significantly different at P< 0.05.
278 A. R. J. MOHD DIN ET AL.
phenolic compounds and antioxidant capacity through were enhanced by treatment of NCE integrated
with different fertilizer approaches (organic and inorganic) compared to other treatments.
Of all the soils tested using organic fertilizer, the nitrogen-fixing bacteria was the major population
among other microbial population (Table 5). It was observed that the total count of nitrogen-fixing bacteria
was 9.7 × 10
6
and 1.4 × 10
6
cfu ml
−1
in the soil treated along with ACE and NCE, respectively. Meanwhile,
the total count of lactic acid bacteria was achieved at 2.9 × 10
4
and 0.15 × 10
4
cfu ml
−1
in soil treated with
ACE and NCE along organic fertilizers, respectively. The lowest lactic acid bacteria count (0.15 × 10
3
cfu ml-
−1
) was recorded at the treatment of NCE along with organic fertilizer. There was a significant difference
(P< 0.05) between the soils which was treated with organic and inorganic fertilizers in terms of total
bacteria and nitrogen-fixing bacteria population. The total bacteria population count was slightly higher
than Pseudomonas sp. in both of the soil treated with ACE and NCE. Based on the soils which was fertilized
with inorganic fertilizer, the total count of bacteria population was highest at 7.5 × 10
7
(ACE-treated soil)
and 5.1 × 10
7
cfu ml
−1
(NCE-treated soil), respectively. The total count of microbial populations increased
with compost extract and fertilizer treatments may be due to compost extract contained a lot of macro-
nutrients that affected soil fertility. Yeast population from the treatment of NCE along with both organic
(5.1 × 10
3
cfu ml
−1
) and inorganic (3.7 × 10
3
cfu ml
−1
) fertilizer-treated soil produced the lowest population
of all the microbial population tested. The results of the yeast population showed no significant difference
(P> 0.05) where it has been observed for all of the tested soil types.
Discussion
Compost extract is perceived as a potential alternative nutrient source to synthetic chemical fertilizers.
Compost extracts are regarded as the simplest technology for the sustainable cultivation agronomic
practices while generally considered to be effective in controlling crop diseases. As in the present case, it is
likely that the presence of the diverse beneficial microorganism communities in compost extracts help in
producing the growth improvement. Although number of studies indicated the increasing microbial
population in compost extract linked to suppression mechanism in crop diseases, the benefit for crop
betterment seems crucial for plant growth promotion irrespective of the method of compost extract
preparation (El-Gizawy, Shalaby, and Mahmoud 2014; Hargreaves, Adl, and Warman 2009). There is an
argument on the incubation period for preparation of compost extracts regardless of the nutrient
additives and source of compost used. Siddiqui et al. (2009) prepared ACE and brewed it for 12 days
prior using it as a disease suppressor for crop pathogen in okra. Moreover, the incubation period of
compost extract prepared by Koné et al. (2010) required 14 days, whereas Naidu et al. (2010)recom-
mends 7 days of incubation. The present study was similar to Naidu et al. (2010) that sufficient
Table 4. Effect of conjunctive use of nutrient sources on total phenolics and antioxidant capacity (DPPH assay).
Treatment Total phenolic content (mg GAE g
−1
) Antioxidant capacity (mg ml
−1
)
Organic + ACE 825.93
a
717.02
a
Organic + NCE 829.29
a
1018.87
b
Inorganic + ACE 824.12
a
1014.16
b
Inorganic + NCE 825.58
a
1164.85
b
Means with the same letters within a column are not significantly different at P< 0.05.
Table 5. Microbial analysis in soil treated with different nutrient sources.
Compost tea
treatment
Lactic acid bacteria
(cfu ml
−1
)
Total bacteria
(cfu ml
−1
)
Pseudomonas sp.
(cfu ml
−1
)
Yeast
(cfu ml
−1
)
Nitrogen-fixing bacteria
(cfu ml
−1
)
Organic + ACE 2.9 × 10
4a
0.0935 × 10
7a
1.69 × 10
5b
10.4 × 10
3b
9.7 × 10
6a
Organic + NCE 0.15 × 10
4a
0.072 × 10
7a
3.75 × 10
5a
5.1 × 10
3a
1.36 × 10
6b
Inorganic + ACE 1.45 × 10
4a
7.5 × 10
7b
4.45 × 10
5a
9.8 × 10
3b
4.05 × 10
6c
Inorganic + NCE 12.6 × 10
4b
5.1 × 10
7b
1.23 × 10
5ab
3.7 × 10
3a
1.87 × 10
6b
Means with the same letters within a column are not significantly different at P< 0.05.
COMMUNICATIONS IN SOIL SCIENCE AND PLANT ANALYSIS 279
incubation length is needed to promote plant growth. NCE was better compared to ACE as suggested by
Scheuerell and Mahaffee (2006). From the result of the assay, it could be explained that the efficacy of
NCE through multiple mechanisms including microbial antagonism and suppressive effect over plant
pathogens in the soils may advocate the plant growth (Koné et al. 2010).
In this study, the combination use of ACE and inorganic fertilizer significantly produced the maximum
values compared to the other treatments which may be attributed to the pronounced increase in vegetative
growth traits of pak choi in term of fresh weight, dry weight, shoot length, and root length. This treatment is
influenced by the interaction of ample nutrients and growth-promoting hormones present in ACE which
may have boost the maximum biomass yields and also accelerated the growth of the vegetative parts of
plants.El-Gizawy,Shalaby,andMahmoud(2014) explained the increase yield of sugar beet crop at the rate
of 6.28 ton ha
−1
due to the role of N in promoting the meristematic activity that lead to cell enlargement.
This result was in harmony with Mahmoud, El-Gizawy, and Geries (2015) who have mentioned the
beneficial effect of compost extract along with inoculation of N
2
fixing bacteria plus 286 kg N ha
−1
of
mineral fertilizers on onion bulb yield where the nutrient uptake for plant growth was increased. They all
mentioned that compost extract increased vegetative growth and better nutrient uptake due to both supply
nutrients and beneficial microbial functions. It seems that all the treatments utilizing both fertilizer
approaches consistently improved plant growth. In addition, previous studies found by Siddiqui et al.
(2011) and Pant et al. (2009) were also consistent with our study, whereby compost extract and inorganic
fertilizers played a significant role in all of the plants tested by increasing nutrient availability in soils and
improving the nutrient uptake of each plant. This conjunctive use of these two nutrient sources improved
water use efficiency and photosynthetic activity which consequently affect the morphological appearance of
crop. Besides, humic and fulvic acids secreted from the interaction of root–rhizosphere bacteria after
application of compost extract into soil was foundtobebeneficialtopromotecucumbergrowthas
mentioned by Xu et al. (2012). Even, natural auxin and cytokinin-like substances were produced by
beneficial microorganisms in compost extract reported by Scaglia, Pognani, and Adani (2015). We suggest
that these important growth regulators played a significant role in plant yield, even we didn’tmeasureinthe
present case study. Also, Pant et al. (2009) reported the effect of the interaction between organic sources
from composted material and inorganic fertilizers (Osmocote) on mineral content concentration in
vegetable leaf tissue. Our study showed that the root length of the plants treated with ACE and inorganic
fertilizer was the longest in length compared with the others. It could be illustrated that the relationship of a
good equilibrium of two sources (compost extract and fertilizers) resulted in an increment of root surface
area per unit of soil volume, thus directly support the positive physiological measurement in plants. It was
described by Shen et al. (2013) that excessive N application could result in inhibit root morphological
development as N content was found higher in NCE along with readily available N released by inorganic
fertilizers (Table 1). As we could hypothesize that increased root length will help better nutrient uptake and
stimulate plant growth. With reference to the increase of the total root length, Siddiqui et al. (2011)also
experimented with Centella asiatica which was treated with conjunctive use of compost extract and half
dosage of inorganic NPK (50:25:25 kg ha
−1
), leading to an increase in all aspect of morphological growth
and secondary metabolite compounds which matched our results.
Compost extract has ability to mineralize soil organic matter and subsequently stimulate soil fertility,
increase soil microbial activity, and improve soil structure(Verma et al. 2015). As the vegetables need the
continuous supply of nitrogen, biological resources such as amended compost extract with inorganic
fertilizer help to maintain soil organic matter at the adequate level. The bioaugmented compost with EM
along inorganic fertilizer (N
50
P
30
K
25
) showed a significantly higher microbial activity, reflecting
increased dehydrogenase enzyme and microbial biomass in soil. This will help the plant to absorb the
nutrients in soil after mineralization process. Our results proved that plant-treated ACE + inorganic
fertilizers provided slightly higher value of total bacteria count, Pseudomonas, and yeast populations. A
significantly higher N content in pak choi extract was due to the improved effect of nitrogen-fixing
bacteria found in the organic + ACE-treated soil. Although the production of nutrient-solubilizing
enzymes such as nitrogenase and phosphatase activities were not determined, we suggest that presence of
nitrogen-fixing bacteria in the soil provides an indication of changes in soil fertility and thereby
280 A. R. J. MOHD DIN ET AL.
improved N and P mobilization. Aseri et al. (2008) studied that the co-inoculation of A.
chroococcum +Glomus mossae had significantly enhanced activity of alkaline phosphatase and nitro-
genase in the rhizosphere soil of pomegranate (Punica granatum). Microbial population in NCE was
more pronouncedly higherthan ACE but the effect on plant nutrient uptake was comparably equivalent.
Phenolic contents played a crucial role in advocating the physiological properties such as anti-
inflammatory, antimicrobial, hypoglycemic, and antiviral (Navarro-González et al. 2011). It is said that
the leafy part of pak choi (B. rapa cv. chinensis) contained the most considerable phenolic compounds
(Lin and Harnly 2010). Organically grown pak choi and other Brassica family have high levels of
caretonoids, glucosinolates, vitamin C, and phenolic compounds compared to conventionally grown
vegetables (Young et al. 2005). Variation in phenolic compounds would happen and be dependent on
what variety was used, maturity age during harvesting, cultivation system, soil condition, and post-
harvest treatment (Jeffery et al. 2003;Kurilichetal.2002;LisiewskaandKmiecik1996; Vallejo, Tomás-
Barberán, and García-Viguera 2002). In this current study, it validated that the application of organic
fertilizers for both ACE and NCE increased the phenolic content in pak choi extracts. Similarly, Verma
et al. (2015) also reported a higher level of phenolic and lycopene content in tomatoes grown organically.
In their study, lycopene content was achieved at 5.98 mg g
−1
fresh weight by application of EM as an
organic source. Phenolic content was not significantly influenced (P> 0.05) by the fertilizer treatments in
this study and the content was almost equal, although a higher phenolic content was observed in the pak
choi extract when a combination of ACE and organic fertilizers was used. This could be explained by low
nitrogen status in organic fertilizer that has led to maximum phenolic content in pak choi tissue. Estiarte
et al. (1994) suggested that C-based defensive properties including phenolics were formed in a greater
concentration at low nitrogen content (nutrient stress). It was associated with carbon/nutrient balance
hypothesis which explain an excessively large portion of C will act as the defensive properties against crop
diseases and channel into secondary phenolic compound production (Hamilton et al. 2001). In addition,
our study was conducted mimicry to organic agronomic practice and being exposed to over UV exposure
and pest pathogen attack, thus synthesis of high phenolic compounds which initiated by the key entry
enzyme; phenylalanine ammonia lyase was correlated to these stress biotic factors (Naoumkina et al.
2010; Sarma et al. 2015). This phenomenon should be investigated more to describe their respective
mechanisms leading to maximum increase in concentration of phenolic compounds. The antioxidant
properties of vegetables acted by inhibiting the carcinogenesis phase and capable of scavenging free
radicals or oxidative stress (Podsedek 2007). These properties literally increased when the root absorbed
more organic nutrients with relation to the root–rhizosphere induction (Shen et al. 2013). Our study
reported that the higher antioxidant value was significantly greater receiving NCE augmented with
inorganic fertilizers.This was due to the combined effect of microbial consortium in compost extract and
ample supply of major nutrients present in the inorganic fertilizer. As the pak choi was applied with
inorganic fertilizer, the antioxidant activity was observed to be higher. It is said that an increase in
antioxidant was the response of plant protection against pathogens. This increase was associated with the
possibility of allocation of antioxidant resources by the production of antimicrobial compounds such as
phytoalexins (Winter and Davis 2006). Our result of low antioxidant capacity of ACE along with organic
fertilizers was in line with Pant et al. (2009) that demonstrated the minimum phytochemical compounds
are present whilst utilizing aerated vermicompost extract.
Another interesting feature is that the integrative use of these nutrient sources for fertilization purpose
perpetually enhanced the nutrient contents of the pak choi leaf. N, P, and K levels in plant tissue also
showed variable response and subjected to have little effect on the phenolic compound production. This
could be attributed to either or both physiochemical properties of the compost extract that includes the
method of preparation, aeration time, storage time, and compost maturity. Although the total bacteria
counts in ACE-treated soils had the highest populations than NCE-treated soils (Table 5), this result does
not effectively contribute or correlate with the nutrient mineral concentration in plant tissue. Our results
are in agreement with the findings by Omar et al. (2012) where the organic sources of fertilizer have led to
an enhanced level of total phenolic compounds in cassava. However, Knewtson, Griffin, and Carey
(2009) had conversely found that compost extracts did not effect on spinach and collard green yield.
COMMUNICATIONS IN SOIL SCIENCE AND PLANT ANALYSIS 281
Thus, they found that none of compost extracts did improve plant nutrient uptake at all. The effect of
ACE on total N content of pak choi was significantly greater than others. However, Hargreaves, Adl, and
Warman (2009) stated that when fertilizer and compost were combined with NCE, it does not influence
the N content of the strawberry’s leaf tissues. In some cases, it was shown in our study that NCE had
increased P and K elements which was in line with Siddiqui et al. (2011). There was no increase in
mineral concentrations of macro- and micronutrient (N, Mg, Ca) of plant tissue indicating that ACE
provided the least amount of nutrient. NCE augmented with inorganic fertilizers had facilitated greater
uptake of P and K by pak choi extracts. This result also has led to increase oflactic acid bacteria in the soil
tested (Table 5). The higher P uptake due to lactic acid-producing bacteria is attributed to the
solubilization of mineral phosphate which H+ ions excretion takes place under root–rhizosphere
interaction. This was in line with Khalid et al. (2014) who have reported the similar results in tomato.
This could also be explained by a sufficient population of phosphate-solubilizing bacteria in all of the
soils tested such as Pseudomonas sp. which helped in mineralizing insoluble form of phosphorus in root–
rhizosphere into soluble substances for mineral uptake (Nishanth and Biswas 2008). Shrestha, Walsh,
and Midmore (2012) also added that the high rate of compost extract application (92 l per pot) as a soil
drench into the root zone could directly increase plant nutrition. Besides, the use of compost extract
helped to reduce the high leaching of nitrogenous fertilizers and increase Mg nutrient content. The study
done by Omar, Ahmed, and Majid (2015) also proved that this hypothesis where compost amended with
urea and zeolite could stabilize N availability in the soil, thus reducing the nitrogen leaching. Moreover,
incorporation of enriched compost composition in soil mixture and application of compost extract in
this study also provided favorable conditions for improvement in soil that helped to increase nutrient
uptake for plant growth.
Conclusion
The co-application of inorganic fertilizers and compost extract was the best fertilizer strategy to enhance
the vegetative growth of the pak choi vegetable. At the same time, it produced relatively higher N content
and improved soil fertility characteristic. There is a clear interaction between NCE and inorganic
fertilizer, which is the key to increase pak choi yield quantitatively and qualitatively. The effectiveness
of NCE + inorganic fertilizers was shown through the enhanced mineral content (P, K, Mg, and Ca
contents) and also increased the antioxidant capacity of the pak choi leaf extracts. From the practical
point of view, the integrative use of compost extract with nutrient sources could be suggested as an eco-
friendly fertilization strategy as it will cut the total chemical-based inorganic fertilizer dependency.
References
Aseri, G. K., N. Jain, J. Panwar, A. V. Rao, and P. R. Meghwal. 2008. Biofertilizers improve plant growth, fruit yield,
nutrition, metabolism and rhizosphere enzyme activities of Pomegranate (Punica granatum L.) in Indian Thar
Desert. Scientia Horticulturae 117:130–35. doi:10.1016/j.scienta.2008.03.014.
Ashby, S. F. 1907. Some observations on the assimilation of atmospheric nitrogen by a free living soil organism.—
Azotobacter chroococcum of Beijerinck. The Journal of Agricultural Science 2:35–51. doi:10.1017/
S0021859600000988.
Azlim Almey, A. A., C. Ahmed Jalal Khan, I. Syed Zahir, K. Mustapha Suleiman, M. R. Aisyah, and K. Kamarul
Rahim. 2010. Total phenolic content and primary antioxidant activity of methanolic and ethanolic extracts of
aromatic plants leaves. International Food Research Journal 17:1077–84.
Cartea, M. E., M. Francisco, P. Soengas, and P. Velasco. 2011. Phenolic compounds in Brassica vegetables. Molecules
16:251–80. doi:10.3390/molecules16010251.
El-Gizawy, E., G. Shalaby, and E. Mahmoud. 2014. Effects of tea plant compost and mineral nitrogen levels on yield
and quality of sugar beet crop. Communications in Soil Science and Plant Analysis 45:1181–94. doi:10.1080/
00103624.2013.874028.
Estiarte, M., I. Filella, J. Serra, and J. Pefiuelas. 1994. Effects of nutrient and water stress on leaf phenolic content of
peppers and susceptibility to generalist herbivore Helicoverpa armigera (Hubner). Oecologia 99:387–91. doi:10.1007/
BF00627753.
282 A. R. J. MOHD DIN ET AL.
Fritz, J. I., I. H. Franke-Whittle, S. Haindl, H. Insam, and R. Braun. 2012. Microbiological community analysis of
vermicompost tea and its influence on the growth of vegetables and cereals. Canadian Journal of Microbiology
58:836–47. doi:10.1139/w2012-061.
Hamilton, J. G., A. R. Zangerl, E. H. DeLucia, and M. R. Berenbaum. 2001. The carbon & nutrient balance hypothesis:
Its rise and fall. Ecology Letters 4:86–95. doi:10.1046/j.1461-0248.2001.00192.x.
Hargreaves, J. C., M. S. Adl, and P. R. Warman. 2009. Are compost teas an effective nutrient amendment in the
cultivation of strawberries? Soil and plant tissue effects. Journal of the Science of Food and Agriculture 89:390–97.
doi:10.1002/jsfa.v89:3.
Jeffery, E. H., A. F. Brown, A. C. Kurilich, A. S. Keck, N. Matusheski, B. P. Klein, and J. A. Juvik. 2003. Variation in
content of bioactive components in broccoli. Journal of Food Composition and Analysis 16:323–30. doi:10.1016/
S0889-1575(03)00045-0.
Khalid, I., A. Nadeem, R. Ahmed, and A. Husnain. 2014. Conjunctive and mineralization impact of municipal solid
waste compost and inorganic fertilizer on lysimeter and pot studies. Environmental Technology 35:487–98.
doi:10.1080/09593330.2013.833641.
Kim, M. J., C. K. Shim, Y. K. Kim, S. J. Hong, J. H. Park, E. J. Han, J. H. Kim, and S. C. Kim. 2015. Effect of aerated
compost tea on the growth promotion of lettuce, soybean and sweet corn in organic cultivation. The Plant
Pathology Journal 31:259–68. doi:10.5423/PPJ.OA.02.2015.0024.
Knewtson, S. J. B., J. J. Griffin, and E. E. Carey. 2009. Application of two microbial teas did not affect collard or
spinach yield. HortScience 44:73–78.
Koné, S. B., A. Dionne, R. J. Tweddell, H. Antoun, and T. J. Avis. 2010. Suppressive effect of non-aerated compost teas
on foliar fungal pathogens of tomato. Biological Control 52:167–73. doi:10.1016/j.biocontrol.2009.10.018.
Kurilich, A. C., E. H. Jeffery, J. A. Juvik, M. A. Wallig, and B. P. Klein. 2002. Antioxidant capacity of different broccoli
(Brassica oleracea) genotypes using the oxygen radical absorbance capacity (ORAC) assay. Journal of Agricultural
and Food Chemistry 50:5053–57. doi:10.1021/jf025535l.
Lin, L.-Z., and J. M. Harnly. 2010. Phenolic component profiles of mustard greens, yu choy, and 15 other Brassica
vegetables. Journal of Agricultural and Food Chemistry 58:6850–57. doi:10.1021/jf1004786.
Lisiewska, Z., and W. Kmiecik. 1996. Effects of level of nitrogen fertilizer, processing conditions and period of storage
of frozen broccoli and cauliflower on vitamin C retention. Food Chemistry 57:267–70. doi:10.1016/0308-8146(95)
00218-9.
Mahmoud, E., E. El-Gizawy, and L. Geries. 2015. Effect of compost extract, N
2
-fixing bacteria and nitrogen levels
applications on soil properties and onion crop. Archives of Agronomy and Soil Science 61:185–201.
Naidu, Y., S. Meon, J. Kadir, and Y. Siddiqui. 2010. Microbial starter for the enhancement of biological activity of
compost tea. International Journal of Agriculture & Biology 12:51–56.
Naoumkina, M. A., Q. A. Zhao, L. Gallego-Giraldo, X. B. Dai, P. X. Zhao, and R. A. Dixon. 2010. Genome-wide
analysis of phenylpropanoid defence pathways. Molecular Plant Pathology 11:829–46.
Navarro-González, I., V. García-Valverde, J. García-Alonso, and M. J. Periago. 2011. Chemical profile, functional and
antioxidant properties of tomato peel fiber. Food Research International 44:1528–35. doi:10.1016/j.
foodres.2011.04.005.
Nishanth, D., and D. R. Biswas. 2008. Kinetics of phosphorus and potassium release from rock phosphate and waste
mica enriched compost and their effect on yield and nutrient uptake by wheat (Triticum aestivum). Bioresource
Technology 99:3342–53. doi:10.1016/j.biortech.2007.08.025.
Oliveira, E. D., F. A. Santana, L. C. Oliveira, and V. S. Santos. 2015. Genotypic variation of traits related to quality of cassava
roots using affinity propagation algorithm. Scientia Agricola 72:53–61. doi:10.1590/0103-9016-2014-0043.
Omar, L., O. H. Ahmed, and N. M. A. Majid. 2015. Improving ammonium and nitrate release from urea using
clinoptilolite zeolite and compost produced from agricultural wastes. The Scientific World Journal 2015:1–12.
doi:10.1155/2015/574201.
Omar, N. F., S. A. Hassan, U. K. Yusoff, N. A. P. Abdullah, P. E. M. Wahab, and U. R. Sinniah. 2012. Phenolics,
flavonoids, antioxidant activity and cyanogenic glycosides of organic and mineral-base fertilized cassava tubers.
Molecules 17:2378–87. doi:10.3390/molecules17032378.
Pane, C., G. Celano, and M. Zaccardelli. 2014. Metabolic patterns of bacterial communities in aerobic compost teas
associated with potential biocontrol of soilborne plant diseases. Phytopathologia Mediterranea 53:277–86.
Pant, A. P., T. J. K. Radovich, N. V. Hue, and N. Q. Arancon. 2011. Effects of vermicompost tea (Aqueous Extract) on
pak choi yield, quality, and on soil biological properties. Compost Science & Utilization 19:279–92. doi:10.1080/
1065657X.2011.10737010.
Pant, A. P., T. J. K. Radovich, N. V. Hue, and R. E. Paull. 2012. Biochemical properties of compost tea associated with
compost quality and effects on pak choi growth. Scientia Horticulturae 148:138–46. doi:10.1016/j.
scienta.2012.09.019.
Pant, A. P., T. J. K. Radovich, N. V. Hue, S. T. Talcott, and K. A. Krenek. 2009. Vermicompost extracts influence
growth, mineral nutrients, phytonutrients and antioxidant activity in pak choi (Brassica rapa cv. Bonsai, Chinensis
group) grown under vermicompost and chemical fertiliser. Journal of the Science of Food and Agriculture 89:2383–
92. doi:10.1002/jsfa.v89:14.
COMMUNICATIONS IN SOIL SCIENCE AND PLANT ANALYSIS 283
Parthasarathy, S., J. Azizi, S. Ramanathan, S. Ismail, S. Sasidharan, M. I. M. Said, and S. M. Mansor. 2009. Evaluation
of antioxidant and antibacterial activities of aqueous, methanolic and alkaloid extracts from mitragyna speciosa
(Rubiaceae Family) leaves. Molecules 14:3964–74. doi:10.3390/molecules14103964.
Podsędek, A. 2007. Natural antioxidants and antioxidant capacity of Brassica vegetables: A review. LWT - Food Science
and Technology 40:1–11. doi:10.1016/j.lwt.2005.07.023.
Sanwal, S. K., K. Laxminarayana, D. S. Yadav, N. Rai, and R. K. Yadav. 2006. Growth, yield and dietary antioxidants of
broccoli as affected by fertilizer type. Journal of Vegetable Science 12:13–26. doi:10.1300/J484v12n02_03.
Sarma, B. K., S. K. Yadav, S. Singh, and H. B. Singh. 2015. Microbial consortium-mediated plant defense against
phytopathogens: Readdressing for enhancing efficacy. Soil Biology & Biochemistry 87:25–33. doi:10.1016/j.
soilbio.2015.04.001.
Scaglia, B., M. Pognani, and F. Adani. 2015. Evaluation of hormone-like activity of the dissolved organic matter
fraction (DOM) of compost and digestate. Science of the Total Environment 514:314–21. doi:10.1016/j.
scitotenv.2015.02.009.
Scheuerell, S. J., and W. F. Mahaffee. 2006. Variability associated with suppression of gray mold (Botrytis cinerea)on
geranium by foliar applications of nonaerated and aerated compost teas. Plant Disease 90:1201–08. doi:10.1094/PD-
90-1201.
Sharma, R. C., and P. Banik. 2014. Vermicompost and fertilizer application: Effect on productivity and profitability of
baby corn (Zea mays L.) and soil health. Compost Science & Utilization 22:83–92. doi:10.1080/
1065657X.2014.895456.
Shen, J., C. Li, G. Mi, L. Li, L. Yuan, R. Jiang, and F. Zhang. 2013. Maximizing root/rhizosphere efficiency to improve
crop productivity and nutrient use efficiency in intensive agriculture of China. Journal of Experimental Botany
64:1181–92. doi:10.1093/jxb/ers342.
Shrestha, K., K. B. Walsh, and D. J. Midmore. 2012. Microbially enhanced compost extract: Does it increase
solubilisation of minerals and mineralisation of organic matter and thus improve plant nutrition? Journal of
Bioremediation and Biodegradation 3:149. doi:10.4172/2155-6199.
Siddiqui, Y., T. M. Islam, Y. Naidu, and S. Meon. 2011. The conjunctive use of compost tea and inorganic fertiliser on
the growth, yield and terpenoid content of Centella asiatica (L.) urban. Scientia Horticulturae 130:289–95.
doi:10.1016/j.scienta.2011.05.043.
Siddiqui, Y., S. Meon, R. Ismail, and M. Rahmani. 2009. Bio-potential of compost tea from agro-waste to suppress
Choanephora cucurbitarum L. the causal pathogen of wet rot of okra. Biological Control 49:38–44. doi:10.1016/j.
biocontrol.2008.11.008.
Tandon, H.L.S. 1993. Analysis of soils for pH, EC and available major nutrients. In Methods of Analysis of Soils, Plants,
Waters and Fertilizers, ed. H.L.S. Tandon, 36–48. New Delhi, India: Fertilizer Development and Consultation
Organization.
Vallejo, F., F. A. Tomás-Barberán, and C. García-Viguera. 2002. Potential bioactive compounds in health promotion
from broccoli cultivars grown in Spain. Journal of the Science of Food and Agriculture 82:1293–97. doi:10.1002/
jsfa.1183.
Verma, S., A. Sharma, R. Kumar, C. Kaur, A. Arora, R. Shah, and L. Nain. 2015. Improvement of antioxidant and
defense properties of Tomato (var. Pusa Rohini) by application of bioaugmented compost. Saudi Journal of
Biological Sciences 22:256–64. doi:10.1016/j.sjbs.2014.11.003.
Winter, C. K., and S. F. Davis. 2006. Organic foods. Journal of Food Science 71:R117–124. doi:10.1111/jfds.2006.71.
issue-9.
Xu, D., Q. Wang, Y. Wu, G. Yu, Q. Shen, and Q. Huang. 2012. Humic-like substances from different compost extracts
could significantly promote cucumber growth. Pedosphere 22:815–24. doi:10.1016/S1002-0160(12)60067-8.
Yee, L. W., E. M. Khairul Ikram, A. B. M. Jalil, and A. Ismail. 2007. Antioxidant capacity and phenolic content of
selected commercially available cruciferous vegetables. Malaysian Journal of Nutrition 13:71–80.
Young, J. E., X. Zhao, E. E. Carey, R. Welti, -S.-S. Yang, and W. Q. Wang. 2005. Phytochemical phenolics in
organically grown vegetables. Molecular Nutrition & Food Research 49:1136–42. doi:10.1002/(ISSN)1613-4133.
284 A. R. J. MOHD DIN ET AL.
