15_paper_ijcas

International Journal of Contemporary Applied Sciences Vol. 2, No. 7, July 2015
(ISSN: 2308-1365) www.ijcas.net
206
Multi-Variant Statistical Analysis Evaluating the Impact of Rhizobacteria
(Pseudomonas fluorescens) on Growth and Yield Parameters of Two Varieties of
Maize (Zea mays. L)
DIARRASSOUBA Nafan1*,
DAGO Dougba Noel1
, SORO Sibirina2
, FOFANA Inza Jesus1
,
SILUE Souleymane1
and COULIBALY Adama1,3
1
UFR Sciences Biologiques Université Péléforo Gon Coulibaly BP 1328 Korhogo, Côte d’Ivoire.
2
UFR agroforesterie Université Jean Lorougnon Guédé BP 150 Daloa, Côte d’Ivoire.
3
UFR Biosciences Université Felix Houphouet Boigny 22 BP 582 Abidjan 22, Côte d’Ivoire.
*Corresponding author, E-mail: nafandiarra@yahoo.fr / nafan.diarassouba@upgc.edu.ci /
dgnoel7@gmail.com
Abstract
The present survey was conducted to study the effects of rhizobacteria Pseudomonas fluorescens
(P. fluorescens) bio-fertilizer on growth and yield parameters of two varieties of maize, DMRESR-
Y and EV99-MRP. The field experiment was conducted in Korhogo (north of Côte d’Ivoire). For
this purpose, we inoculated maize seeds with rhizobacteria P. fluorescens bio-fertilizer at a
concentration of 7 ml.kg-1
. Statistical analysis based on several correlation tests and on variance
principal component analysis (PCA) of R bio-statistical software evidenced that disregarding the
varieties of maize used, both analysed growth and yield parameters were differentially influenced
by the bio-fertilizer. Moreover, the present study evidenced a strong difference in term of dry
biomass, growth and yield parameters between maize plants under treatment T0 (treatment with any
rhizobacteria P. fluorescens) with respect to treatment T1 (treatment with rhizobacteria P.
fluorescens only), T2 (treatment with rhizobacteria P. fluorescens associated to foliar fertilizer) and
T3 (treatment with foliar fertilizer only) suggesting a positive effect of rhizobacteria P. fluorescens
bio-fertilizer on maize growing and produce. We also showed that maize plants treated with the
rhizobacteria P. fluorescens associated to foliar fertilizer (T2 treatment) yielded a high dry biomass
ratio (p-value = 0.006) with respect to the other analysed treatments (T0, T1 and T3).
Key words: Bio-fertilizer; Rhizobacterie Pseudomonas fluorescens, Maize (Zea mays. L)

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1. Introduction
Maize (Zea mays. L) is called king of cereal because of it productivity potential compared to any
other cereal crop (Umesha S. et al., 2014). In Côte d'Ivoire, maize (Zea mays. L) is cultivated in
different agro-ecological zones, alone or in combination with most crops. In this country, maize is
the most cultivated cereal after rice with an annual production estimated to 600,000 tons. Maize is
the staple food for many Ivorian’s. However, it is also involved in animal feed (poultry, pigs, cattle)
and used as a raw material in some industries (brewing, soap and oil mill). The traditional
production of maize yield around 0.8 tons/hectare (tons/ha) against 2-5 tons/ha in the controlled
environment for the selected varieties (Akanvou Louise et al., 2006). Although being a food crop,
maize has also become a cash crop. Being an exhaustive crop, it has very high nutrient requirement
and its productivity is closely depend on nutrient management system. Under the present trend of
the decline of the soil fertility in north of Cote d'Ivoire, maize production in this area facing many
constraints including the productivity of the soil. Some of these problems can be tackled by using
bio-fertilizers, which are natural, beneficial and ecologically friendly. Among the means available
to achieve sustainability in agriculture production, bio-fertilizers plays an important and key role
because it processes many desirable soil properties and exerts beneficial effect on the physical,
chemical and biological characteristics of the soil. Then bio-fertilizers because of it vital role
maintaining long term soil fertility (Hossein S. et al., 2013) could be requested for many
agricultural soils in the north of Côte d'Ivoire. Moreover, they are essential for obtaining good
yields avoiding depleting the soil. In the north of Côte d'Ivoire, the maize production to ensure food
self-sufficiency and substantial income to producers, is still dependent on the intensive use of
chemical fertilizers. This approach is not without negative consequences. The intensive use of
mineral fertilizers can cause problems as the flow of these fertilizers into rivers, lakes and streams
where they constitute a source of pollution (Alalaoui, 2007). It is therefore appropriate to find
alternative solutions at the overuse of chemical fertilizers. Bio-fertilizer are found positive
contribution to soil fertility, resulting in an increase in crop yield without causing any
environmental, water or soil pollution hazards (Umesha S. et al., 2014). Research work has already
been undertaken on the potential effect of bio-fertilizers on crop yields. Hernandez et al. (1995)
claim that inoculation of maize seed with rhizobacteria in combination with a dose of 120 kg/ha of
nitrogen (N), results in an increase of around 25% of returns compared to those obtained with the
same dose of nitrogen but without inoculation with microorganisms. Also, the combination of
rhizobacteria raised with a dose of 120 kg/ha of nitrogen can increase over 60% the maize yields in
comparison with those obtained in plots without nitrogen application or inoculation of bacteria.

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Here, basing on these results and observations, we highlighted the effects of rhizobacterie
Pseudomonas fluorescens (P. fluorescens) bio-fertilizer on both growth and yield parameters of two
varieties of maize through a statistical analysis based on a combination of several tests (Dago et al.,
2015) of R software package (R Core Team, 2013) with the aim to promote its future use as bio-
fertilizers for maize plants (Zea mays. L) in the north of Côte d'Ivoire.
2. Materials and Methods
2.1. Characteristics of the study site
The study was conducted on-farm of the sub prefecture of Napiéledougou in the Department of
Korhogo (north of Côte d'Ivoire). The site is located between an average altitude of 392 meters
between - 5 ° 34 '31" and - 5 ° 29' 34 '' West longitude and between 9 ° 31 '23'' and 9 ° 31' 32 ''
latitude North and 5°38' 83.2'' at an average altitude and is at 40 Km from Korhogo .The climate in
this area is characterized by two types Sudanese seasons: a dry season, from November to April,
punctuated by the Harmattan (dry wind from the Sahel) and a rainy season from May to November.
This area is irrigated by the rivers Bandama and Solomougou. The climate of the area is the
maritime sub-equatorial with the temperatures that range between 24 and 33°C and the annual
precipitation that vary between 1100mm and 1600 mm (Anonymous, 2006).
2.2. Maize Seed Material
The production cycle of DMRESR-Y (yellow colour) and EV99-MRP (white colour) exhibits the
same duration (short cycle; 90-95 days) with an annual production comprised between 2 and 4
tons/ha. The variety EV99-MRP contain more proteins with respect to DMRESR-Y variety and
displays a relative tolerance to drought. The improve seed of these maize varieties are available at
the National Agricultural Research Centre (CNRA of Côte d'Ivoire).
2.3. Experimental Design
The experimental design consisted in a block of 4 treatments and 4 repetitions. The two blocks
corresponding to each of the two analysed maize varieties were divided into 16 basic plots
corresponding to the four different treatments (T0, T1, T2 and T3). The space between the ridges
was 75 cm between rows and 40 cm between bunches with 2 plants per hill after thinning. The
various treatments have covered each elementary plot of 4m x 4m (16 m²). Each elementary plot
contained 4 lines of 4 m long.
The four treatments were as follows: T0: plots planted without rhizobacteria P. fluorescens and
without foliar fertilizer; T1: subdivision sown with the seed inoculated with rhizobacteria P.

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fluorescens only; T2: land sown with the seed inoculated with rhizobacteria P. fluorescens bio-
fertilizer and foliar fertilizer; T3: subdivision without rhizobacteria P. fluorescens bio-fertilizer with
foliar fertilizer only. Moreover, a regular weeding (once a month) was made for the maintenance of
the plot. The present experimental design have been performed in the raining season then no
watering were made on the analysed maize plants outside the rain.
2.4. Preparation of Inoculums and Seed Inoculation
Rizofos Liq Maize Bio fertilizer manufacture requires the strain of bacterium Pseudomonas
fluorescens specifically selected for its phosphorus solubilizing ability. If stored under the
recommended conditions (cool below 25°C), the product contains 1x109 CFU/ml in manufacturing.
The inoculums were prepared from 500 ml Rizofos Liq Maize Premax-R + 200 ml of Premax-R for
100 kg of maize seed. We put the needed amount of Premax-R in a container and then added the
required amount of Rizofos Liq Maize. We mix until a homogeneous mixture before inoculation of
the required amount of seed. What follows is planting seeds making holes about 3 cm deep, in
which two inoculated seed of maize are deposited.
2.5. Growth and Production Measured Parameters
During this study, growth and yield parameters were measured, on each plant in the two considered
experimental site.
2.5.1. Growth Parameters
Six features were evaluated during the growth phase (i) height of the plant, (ii) dry biomass, (iii)
number of leaves, (iv) length of leaves, (v) width of the leaves and (vi) the diameter of the collar
which has been measured using an electronic sliding calliper. The growth parameters were
evaluated using a centimeter as scale of measurement (cm).The height of the plants have been
measured from the ground level to the end of the longest petiole. The number of leaves per plant
was counted weekly. For the estimation of dry biomass, we first determined the fresh weight of the
vegetative material and next we dry the material by using an oven-dried for 48 hours (at a
temperature of 60 ° C: time and temperature required for a constant dry weight). The weights were
measured using a precision balance 10-4 g (Toledo). Dry biomass was calculated using the
following formula:
Dry biomass = [(Fresh weight of leaves)×( dry weight of the leave sample )/( Fresh weight of the
leave sample )]+[(fresh weight rods )x(dry weight of the sample rod )/( wet weight of the sample
rods )].

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2.5.2.Yield or Production Parameters.
Five features were evaluated during the production phase (i) length of the ears length (ii) width of
the ears, (iii) geometric diameter of the ears (iv) number of seed per ear or spike and (v) number of
ear per plant. Length, width and the geometric diameter parameters have been measured by using an
electronic calliper.
2.6. Statistical Analysis Based on R Software.
R is a free software environment for bio-statistical computing and graphics. For the present study
and analysis, we processed our own script (R version 3.2.0). Then, we performed several correlation
tests (Spearman and Pearson correlation tests) between both growth and yield parameters. We also
estimated the variance of 8 analyzed parameters (4 growth and 4 yield parameters) by performing
the principal component analysis (PCA) based on R software. The evaluation of the variance
estimation, due to the large multivariate datasets have been processed by the principal component
analysis to reduces the dimensionality of the analyzed parameter. The PCA facilitates the
observation of different behavior among all analyzed parameters evaluating the effect of the bio-
fertilizer on plant growth and yield. This analysis have been performed on 41 samples for each
considered parameter in the two considered experimental sites.
Multi-variant analysis based on boxplot representation have been performed with the aim to
estimate the variability of each analyzed parameters (8 parameters) processed by the bio-fertilizer.
In descriptive statistics, boxplot is a convenient way of graphically depicting groups of numerical
data through their quartiles. Box plots are non-parametric and they display variation in samples of a
statistical population without making any assumptions of the underlying statistical distribution. The
spacing’s between the different parts of the box indicate the degree of dispersion (spread) in the
data, and show outliers (Rousseeuw, P. J et al., 1999).
3. Results
3.1. Impact of the Rhizobacteria Bio-fertilizer on Both DMRESR-Y and BEV99-MRP Maize
Varieties.
Correlation test in R statistical analysis (cor.test) have been used to evaluate the association
between paired parameters. In order to corroborate the effect of the rhizobacteria bio-fertilizer on
the two varieties of maize, we applied a correlation test (i) between the six examined growth
parameters (height of the plant, dry biomass, number of leaves, length of leaves, width of leaves and
diameter of the collar) and (ii) between the five considered production parameters (ears length, ears

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width, number of ear per plant, geometric diameter of the ear and number of seed per spike). The
present analysis have been accomplished basing on the mean values of each analysed parameters
and revealed a high and significant correlation values between all features assessed for (i) growth
and (ii) yield parameters. In fact the correlation values obtained for these surveys were higher than
0.75 (R: 0.76-0.98) with an associated p-value that ranged between 4.868e-07 and 8.882e-16.
Taking together, these results suggested that the impact of rhizobacteria P. fluorescens bio-fertilizer
on the development of the analysed maize plants is relatively associated to the examined varieties.
3.2. Spearman Correlation Evaluating the Effect of Bio-fertilizer Treatment on Both
Growth and Yield Parameters.
Next, we investigated the effect of each treatment (T0, T1, T2 and T3) on both maize growth and
yield parameters. The Spearman correlation analysis showed that disregarding (i) the analysed
parameters, (ii) the variety of maize and (iii) the experimental parcel, all maize plants under T0
treatment (treatment without bio-fertilizer) exhibited a very high correlation value among
themselves as reported in Fig. 1 (R > 0.95 at a p-value ≤ 0.001). These results presume that growth
parameters are good predictors of yield parameters in maize plants under treatment T0 (maize
without any bio-fertilizer treatment). In other words, the variability between the different analysed
features of both growth and yield parameters under treatment T0 is low. Moreover, the same
analysis exhibited a weak correlation between maize plants under treatment T0 and the plants under
treatments T1, T2 and T3 (correlation values range from -1 to 0.5; p-value ≤0.0001) as reported in
figure 1. In view of the foregoing, these results suppose that maize plants under bio-fertilizer
treatment (T1, T2 and T3) exhibit a strong difference with maize plants without any bio-fertilizer
treatment (T0). However, when compared among them, maize plants under treatment T1, T2 and T3
display a heterogeneous correlation between themselves (Fig. 1) (correlation values range from 0.90
to -1; p-value ≤ 0.0001), suggesting a strong variability between analysed features of both growth
and yield parameters. Taking together, these results reveal the strong influence of rhizobactéries P.
fluorescens bio-fertilizer on maize growth and yield.

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Figure 1. Spearman correlation showing the effect of rhizobacteria P. fluorescens bio-fertilizer
treatment on both yield (production) and growth parameters in maize plant (Zea mays. L).
3.3. Evaluation of Growth and Yield Parameters by a Boxplot Multi-Variant Analysis.
We processed a multi-variant statistical analysis of 8 features of both growth and yield parameters
(these 8 features have been chosen for this survey because of the availability of their detailed values
for each plant and treatment) by using a boxplot representation. For this statistical analysis and the
others, we developed a script in R environment, highlighting a considerable difference between
growth and yield parameters. The boxplot analysis evidenced tow tendencies estimating a relative
high dispersion for analysed features associated to growth parameters with respect to those
associated to the yield or production parameters. Then, the present boxplot analysis evidenced a
relative small variability in yield or production parameters with respect to in growth parameters.
These results suppose that the two analysed parameter categories (growth and yield or production
parameters) are differentially influenced by the rhizobacteries P. fluorescens bio-fertilizer.
Moreover, while plant length parameter exhibits the highest variability among all features of growth
parameter, ear length results to be the most variable parameters among the production parameters

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(Fig.2). The smallest variability have been observed in the seed number parameter (yield
parameter). Taking together, these observations suggest that rhizobacteries P. fluorescens bio-
fertilizer strongly reduce the variability of yield parameter and in particular those of seed number
(Fig. 2).
Figure 2. Boxplot analysis assessing the effect of rhizobacteria P. fluorescens on the variability of
both growth and production parameters.
3.4. Correlation Test Analysis Between Growth and Yield Parameters.
Next, we performed a correlation analysis between both growth and yield parameters to test for
their agreement reacting to maize bio-fertilizer stimulus (8 parameters as above have been
considered for this analysis). This survey evidenced a high correlation between all analysed growth
feature parameters (R: 0.76-0.96; p-value ≤ 0.001) as reported in Table 1, suggesting a comparative
effect of rhizobacteries P. fluorescens bio-fertilizer on maize plants growth parameters (collar
diameter, plant height, leaves number and leaves length). Moreover, figure 3 displayed a convincing
difference between both growth and yield (ear length, ear width, seed number per ear and ear
diameter) parameters evaluating the effect of rhizobacteria P. fluorescens on maize plant
development. The same analysis exhibited a heterogeneous correlation values between yield
parameter features (R: 0.13-0.81).However, the present results suppose that (i) ear diameter (yield
parameter) is a good predictor of ear width (yield parameter) (R: 0.81 at a p-value ≤0.001) and that
(ii) the seed number per ear and the length of ear parameters displayed a relative good correlation
between themselves (Fig. 3). Taking as whole, this analysis suggests that rhizobactéries P.

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fluorescens bio-fertilizer influences strongly the analysed production parameters. In other words,
yield or production parameters are more sensible to bio-fertilizer effect with respect to growth
parameters (Fig. 3, Table 1).
Figure 3. Clustering dendrogram of Pearson correlation between growth and yield parameters.
Table 1: Value of Pearson correlation between both growth and yield parameters.
Ear
Length
Ear
Width
Ear
Diameter
Number
of Seed
Collar
Diameter
Plant
Height
Number of
Leaves
Ear Width 0.26 1
Ear Diameter 0.13 0.81***
1
Number of
Seed 0.49***
0.35 0.21 1
Collar
Diameter -0.21 0.16 0.29 -0.05 1
Plant Height -0.21 0.22 0.45***
0.06 0.84***
1
Number of
Leaves -0.16 0.09 0.29 -0.01 0.79***
0.82***
1
Leaves Length -0.18 0.13 0.27 -0.06 0.96***
0.79***
0.76***
***
p-value ≤ 0.001; **
0.001<p-value ≤ 0.1 and *
p-value > 0.1

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3.5. Comparison Between Ear Seed Number and Ear Length Parameters by PCA
Analysis (yield parameters).
Because of their relatively good correlation (Fig. 3), we performed a principal component analysis
(PCA) comparing both ear length and ear seed number (two yield parameters). The analysis showed
a high variability in maize plants under T0 treatment for the two analysed parameters (Fig. 4).
However, the PCA survey revealed a strong normalization effect of the rhizobactéries P.
fluorescens bio-fertilizer on both analysed ear length and ear seed number parameters (Fig. 4). This
tendency could explain the relative good correlation between these two parameters as indicated in
figure 3 and table 1. Further, the normalization effect of the bio-fertilizer seem to be relatively less
drastic on ear length parameter with respect to in ear seed number parameter. These results could
explain a relative high variability of ear length parameter in comparison with those of ear seed
number parameter as evidenced in figure 2 (see above).
Figure 4. Effect of rhizobacteria P. fluorescens bio-fertilizer treatment on both maize ear length
and the number of grain per maize ear parameters (ratio of variances 2.20; p-value 0.014).
3.6. Comparison Between Ear Diameter and Ear Width Parameters by PCA Analysis
(yield parameters).
Comparison analysis based on a PCA approach between ear diameter and ear width parameters
(yield parameters) have been performed because of the high correlation between these two features,

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evaluating rhizobacteria P. fluorescens bio-fertilizer impact on maize plants development and yield.
This analysis highlighted and confirmed the stabilization effect of the bio-fertilizer on the maize
plants production parameters (Fig. 5). It noteworthy to observe that the stabilisation effect of
rhizobacteria P. fluorescens bio-fertilizer on these two parameters is less strong in comparison to in
ear seed number parameter (Fig. 4). Moreover, rhizobacteria P. fluorescens bio-fertilizer impact on
ear width parameter is comparable with those on the ear diameter parameter (Fig. 5). This result is
in agreement with the above boxplot analysis and representation which suggested that ear width and
ear diameter yield parameters exhibited a comparable data variability (Fig. 2). This result could also
explain the high correlation degree between these two parameters assessing bio-fertilizer stimulus
effect on the maize plants development. Then, the substantial differences observed between both
figures 4 and 5supports the high sensibility of maize plants production (or yield) parameters to the
rhizobacteria bio-fertilizer.
Figure 5. Effect of rhizobacteria P. fluorescens bio-fertilizer treatment on both ear width and
diameter parameters (ratio of variance 2.63; p-value=0.003).
3.7. Comparison Between Features of Growth Parameter by PCA Analysis.
We next evaluated the effect of rhizobacteria P. fluorescens bio-fertilizer on maize growth
parameters by a PCA analysis showing a moderate stabilisation effect of this bio-fertilizer on
features of growth parameter with respect to those of yield parameter (Fig. 6). These results hint a
high variability of growth parameters with respect to yield parameters, assessing the effect of

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rhizobacteria P. fluorescens bio-fertilizer on maize plants development (Fig.2 see above). The
profile of the PCA analysis curves associated to growth parameters are comparable among
themselves (Panels A and B in Fig. 6). These observations may explain the high correlation value
among these parameters evaluating the effect of the analysed bio-fertilizer on maize plants growth
and development. It is also noteworthy to observe that the treatment T2 having recommended dose
of rhizobacteria P. fluorescens + foliar fertilizer compost recorded the drastic effect on the growth
parameters (Fig. 6). This might be due to more availability of nutrient from compost and beneficial
effect due to rhizobacteria P. fluorescens associated to organic foliar fertilizer inoculation which
provide nitrogen and phosphorus to plant growth. It is interesting to note that treatment T2 impact
maize plants growth parameter acting as an intermediary phase between treatments T1 and T3 as
expected. Taking together, this analysis evidenced a modest normalization effect of rhizobactéries
P. fluorescens bio-fertilizer on maize plant development and support a weak variability of growth
parameters assessing the influence of the former on maize plant increasing process with a particular
attention to treatment T2.
Figure 6. Effect of rhizobacteria P. fluorescens bio-fertilizer fertilizing treatment on the analysed
growth parameters ((A) height of maize plant and collar diameter parameters and (B) leaves length
and number parameters) (ratio of variance: 0.57-0.68; p-value: 0.2-0.07).

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3.8. Pearson Correlation Evaluating the Degree of Agreement Between the Mean Value
of all Analysed Growth and Yield Parameters.
Pearson correlation analysis (Euclidian distance of Pearson correlation) between the mean values of
all analysed growth and yield parameters (11 parameters in total) assessing maize plants
development by rhizobacteria P. fluorescens bio-fertilizer have been performed and evidenced four
tendencies (Fig. 7).This survey showed that assessing the mean values of each factor, yield
parameters exhibited a good clustering among themselves (except ear width parameter) with respect
to growth parameters. In other words, the analysed growth parameters (appraising their mean
values) exhibited a heterogeneous behaviours among themselves in term of Pearson correlation
analysis (Fig. 7). This analysis confirmed the moderate stabilisation effect of the bio-fertilizer on
growth parameters with respect to yield parameters. It is interesting to note that this survey displays
a good agreement between the number of maize ear per plants and the number of leaves per plants
(Fig. 7). However, it is also noteworthy to observe that dry biomass parameter exhibits a different
behaviour with respect the other’s analysed parameters. This might be due to the diverse effect of
rhizobactéries P. fluorescens bio-fertilizer on this parameter in comparison to the others.
Figure 7. Cluster dendrogram of the Euclidian distance of Pearson correlation between the mean
values of the 11 analysed growth and yield parameters (p-value 0.012).

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3.9. Bio-fertilizer Effect on Maize Dry Biomass Parameter.
We performed a statistical t.test based on R software with the aim to evaluate the effect of
rhizobacteria P. fluorescens bio-fertilizer on maize dry biomass parameter. As previously showed
this parameter exhibited different behaviour compared with the other analysed parameters. This
assay emphases a strong difference between dry biomass obtained under T0 treatment and those
detected in T2 treatments (Fig. 8 panels A and B). Moreover, our statistical analysis suggested that
rhizobacteria P. fluorescens and foliar bio-fertilizer respectively improve the ratio of maize dry
biomass (T1and T3 treatments improve the maize dry biomass parameter with respect to treatment
T0). It is noteworthy to observed that treatment T2 having recommended dose of rhizobacteria P.
fluorescens and foliar fertilizer, recorded the highest test dry biomass compared to treatments T1
and T 3 in both parcels 3 and 4 (Fig. 8 panel B). In the other words, a significant difference
assessing the dry biomass parameter has been observed between maize plants under T2 treatment
and the other treated plants (p-value ranged from 0.012 and 0.007). These analysis evidenced the
good effect of rhizobacteria P. fluorescens combined with foliar fertilizer improving maize dry
biomass by providing sufficient nutriment (nitrate and phosphorus) for the maize plants growth
and development.
Figure 8. (A) Barplot of a comparative analysis of the effect of rhizobacteria P. fluorescens
combined with foliar bio-fertilizer on maize dry biomass parameter (B) showing a significant
difference between biomass yielded by treatment T2 with respect to the others treatments (t = 6.881,
df = 3, p-value = 0.006).
A B

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4. Discussion
The present study assessed the effects of rhizobacteria P. fluorescens bio-fertilizer on growth and
yield parameters of two varieties of maize, DMRESR-Y and EV99-MRP.This investigation have
been conducted during rainy season in the north of Cote d’Ivoire and three types of treatments
(treatment T1, T2 and T3) based on the rhizobacteria P. fluorescens bio-fertilizer combined with
foliar fertilizer and/or without foliar fertilizer have been processed (see materials and methods). We
showed that the two analysed varieties of maize; DMRESR-Y and EV99-MRP relatively gave the
same response to rhizobacteria P. fluorescens bio-fertilizer stimulus. However, it is emerged that
maize plants under treatment T0 (planted without rhizobacteria P. fluorescens and without foliar
fertilizer) exhibited a strong difference with respect to maize plants under rhizobacteria P.
fluorescens bio-fertilizer treatment (Fig.1). Our finding also evidenced that rhizobacteria P.
fluorescens bio-fertilizer carry out a high heterogeneity in term of correlation between both growth
and yield parameters suggesting it influence on maize plant development. Moreover, the boxplot
multi variant analysis revealed that rhizobacteria bio-fertilizer favours a high variability in growth
parameters in comparison to yield parameters. Taking together, these results showed that growth
parameters were significantly influenced by the bio-fertilizer treatment. However among the
different features examined for growth and yield parameters, significant increase in maize plant
height and ear length respectively has been observed assessing bio-fertilizer effect on maize plant
growth and yield (Fig. 2). The Pearson correlation analysis demonstrated that both yield
(heterogeneous correlation values) and growth (high correlation values) parameters are strongly
differentially influenced by the bio-fertilizer evaluating maize plant development (Fig. 3). The
principal component analysis (PCA) applied to variance parameter evidenced a strong normalizing
effect of the bio-fertilizer on the yield parameters, showing that rhizobacteria P. fluorescens impact
the maize plants development reducing the variability of their yield parameters (Fig. 4 and 5). It is
interesting to observe that the same investigation highlighted a weak stabilizing effect of the same
bio-fertilizer on growth parameters (Fig. 6). Considering as whole, these results evidenced a
different impacts (two tendencies) of the rhizobacteria P. fluorescens bio-fertilizer on growth and
yield parameters respectively improving maize plants increase and production. However, the
development and the good growth and productivity of maize could be attributed to the enhanced
nutrient use efficiency in the presence of organic fertilizer (Umesha et al., 2014). Moreover,
treatment T2 having recommended dose of rhizobacteria P. fluorescens and foliar fertilizer detailed
a strong effect on the growth parameters (Fig. 6), suggesting a high availability of nutrient and
beneficial effect due to rhizobacteria P. fluorescens associated to organic foliar fertilizer inoculation

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which provide nitrogen and phosphorus to plant growth. Several research studies have showed that
the composted organic materials release nutrients slowly and may reduce the leaching losses,
particularly nitrogen (Naveed et al., 2008). It also emerged from our study that dry biomass
parameter (mean value) exhibits a low correlation with the other analysed parameters (Fig.7). In
fact the normalization effect of the bio-fertilizer on dry biomass parameter is wholly different with
respect to the other’s analysed parameters. Our findings showed that the treatment T2 that results to
be the combination of rhizobacteria P. fluorescens and foliar fertilizer, yielded the highest amount
of maize dry biomass (more than 70 g) in comparison with the treatments T0 (39 g), T1 (49 g) and
T3 (45 g) (Fig. 8 panels A and B) (p-values: 0.006). However, it is noteworthy to observe that
recent study shows that the treatment T2 (bio-fertilizers + foliar fertilizer) is the best recommended
in maize farming. Moreover, even if the efficiency difference shown between T1, T2, T3 treatment
could be attribute to the bio-fertilizers, the applied period, the amelioration (high dry biomass ratio
and strong effect on growth parameters) of the inoculated plants growth could be due to rizobacteria
and foliar fertilizer synergic effect. In fact, several assays proved that rhizobacteria P. fluorescens
associated to foliar fertilizer impacted positively both maize plant growth and maize yielded seeds
on intact soil in the south of Benin (Adjanohoun et al., 2012; Adjanohoun et al., 2011) showing that
87 days after sowing, the inoculated plants of maize with P.fluorescens and P.aeroginosa produce
an average value of dry biomass that significantly exceeded respectively 59,57% and 23,40% of the
dry biomass value of maize plant without any treatment. However, the homogeneity effect of the
bio-fertilizer on the yield parameters and the amelioration of the dry biomass production parameters
were obtained by the action of both rhizobacteries and foliar fertilizer. In fact the inoculation of
maize seeds by the rizobacteries P. fluoresens bio-fertilizer increases the availability of soil in
phosphorus and nitrogen, ameliorates the efficiency of phosphated fertilizer and produces
phytohormones which react as growth factor favouring crops growth (Lee et al., 1970, Kang et al.,
2010). Shaharoona et al. (2006) showed the efficiency of Pseudomonas increasing significantly
maize plant growth and production when adequate quantity of nitrate has been provided. Previous
studies showed that rhizobacteria improve maize productivity increasing the absorption of nitrate,
phosphate, potassium, zinc, manganese, copper and iron (Biari et al., 2010). Furthermore, Walker et
al. (2011) demonstrated the positive effect of rhizobacteria on the maize plant development via
quantitative and qualitative modification of benzoxazinoid compost. Nevertheless, Contesto et al.
(2008) showed that rhizobacteria impact positively plants growth inducing vegetal hormone
synthesis. In the same tendency, Ahmad et al. (2006) and Estes et al. (2004) evidenced the positive
influence of rhizobacteria on plant growth and development through a better seed germination and a

222
greater development of the roots, which induce the increase in the absorption capacity of nutrients
and water in plants. These results and observations are in agreement with our finding. Bringing
these data together, we showed that rhizobacteria associated to the organic foliar fertilizer can be
used to increase or improve the production of maize. However, we are not able to quantify the real
impact of rhizobacteria (organic fertilizer) substituting chemical fertilizer. Even if the combination
of several potentially nitrogen-fixing rhizobacteria is possible, the selection of plants varieties that
favour heterogeneous nitrogen fixation is a new and promising approach.
5. Conclusion
The findings of this study have clearly showed that inoculation of maize seeds by rhizobacteria P.
fluorescens associated with foliar fertilizer has resulted in obtaining highest dry biomass
production, improving maize plant growth and crop yields in the soil of the north of Côte d'Ivoire.
These results bode well for the possibility of using these rhizobacteria as organic fertilizer for
sustainable production of maize. In the dense region of Korhogo where the pressure on land and the
decline of soil fertility constantly threaten agricultural production, the use of bio-fertilizer is a good
alternative to increase agricultural yields. However, the experiment should be conducted on a large
scale to determine the values of the obtained yields and the contribution of these rhizobaterias in
increasing element such as nitrogen, potassium and phosphorus.
Acknowledgements
The authors thank the Rhizobacter Company in Argentina for providing bio-fertilizer and for their
economic support to this work.
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