PLANT GROWTH PROMOTIONAL EFFECT OF DIFFERENT …

www.wjpps.com Vol 5, Issue 6, 2016.

1537

Vijaya et al. World Journal of Pharmacy and Pharmaceutical Sciences

PLANT GROWTH PROMOTIONAL EFFECT OF DIFFERENT

COMBINATIONS OF VERMICOMPOST, PSB AND RHIZOBIUM ON

SORGHUM

Pudur Girija1

and Dr. T. Vijaya2*

1Rayalaseema University, Kurnool – 518002.

2Professor, Department of Botany, S.V. University, Tirupati – 517502.

ABSTRACT

Biofertilizers are the most advanced biotechnological products

necessary to support developing organic agriculture, green agriculture

and sustainable agriculture. Composting is considered to be one of the

most suitable ways of converting organic wastes into products that are

beneficial for plant growth. The most commonly used bio-inoculants to

supply the nutritional need of the plants are phosphorous soluble

microorganisms (PSM), nitrogen fixers (Azotobacter) and

vermicompost. Vermicompost, Azotobacter and PSB inoculum were

prepared and its effect on plant growth was determined in terms of

plant growth parameters and physiological parameters. The results revealed that inoculation

of vermicompost, Azotobacter and PSB enhanced the shoot length, fresh and dry biomass of

root and shoot, number of leaves compared to control plants. The contents of chlorophyll,

carbohydrates, were also found increased in treatment plants. The inoculation of

vermicompost, Azotobacter and PSB was found superior than single inoculum not only in

promoting plant growth, but also in maintaining soil fertility.

KEYWORDS: Vermicompost, PSB (Phosphate Solubilizing Bacteria), Rhizobium,

Sorghum, Azotobacter.

INTRODUCTION

Biofertilizers are the most advanced biotechnological products necessary to support

developing organic agriculture, green agriculture and sustainable agriculture. Biofertilizers

are defined as ready to use live formulates of beneficial microorganisms which on application

WORLD JOURNAL OF PHARMACY AND PHARMACEUTICAL SCIENCES

SJIF Impact Factor 6.041

Volume 5, Issue 6, 1537-1551 Research Article ISSN 2278 – 4357

*Corresponding Author

Dr. T. Vijaya

Professor, Department of

Botany, S.V. University,

Tirupati – 517502.

Article Received on

02 April 2016,

Revised on 23 April 2016,

Accepted on 13 May 2016

DOI: 10.20959/wjpps20166-6940


1538


to seed, root or soil, mobilizes the availability of nutrients by their biological activity and

help to build up the soil micro flora which in turn improves the soil fertility.

Using more local organic materials from agro-industrial by-products as nutrient sources may

help. Composting is considered to be one of the most suitable ways of converting organic

wastes into products that are beneficial for plant growth.[1]

Compost inoculated with N2-

fixing bacteria, which can fix atmospheric nitrogen, solubilized phosphorous and stimulate

plant growth by biosynthesis of plant growth promoting substances (plant growth promoting

rhizobacteria, PGPR) may be particularly useful.[2]

The main sources of biofertilizers are bacteria, fungi and cyanobacteria. The most commonly

used bio-inoculants to supply the nutritional need of the plants are phosphorous soluble

microorganisms (PSM), nitrogen fixers (Azotobacter) and vermicompost. Soil

microorganisms have enormous potential in providing soil phosphates for plant growth.

Phosphorous biofertilizers (Pseudomonas sp.) can help in increasing the availability of

accumulated phosphorous for plant growth by solubilisation.[3]

Most of the soil phosphorus is

in unavailable form and hardly about 1 to 2% of it is incorporated in to the above ground

parts of the plants. Phosphorus is a major growth-limiting nutrient and unlike the case for

nitrogen, there is no large atmospheric source that can be made biologically available.[4]

Efficiency of phosphorus fertilizer throughout the world is around 10-25%[5]

and

concentration of bioavailable phosphorus in soil is very low reaching the level of 1.0mg Kg-1

soil.[6]

Soil microorganisms play a key role in soil phosphorus dynamics and subsequent

availability of phosphate to plants.[7]

Phosphate Solubilizing Bacteria (PSB) are being used as

biofertilizers since 1950s.[8]

Release of phosphorus by PSB from insoluble and

fixed/adsorbed forms is an important aspect regarding phosphorus availability in soils.

Microbial biomass assimilates soluble P and prevents it from adsorption or fixation.[9]

Phosphate solubilization is the result of combined effect of pH decrease and organic acids

production.[10]

Sorghum is one of the main staple food for the world‟s poorest and most food insecure

people. It is known to be cultivated as food grain in Africa and Asia. About 26 percent of the

Indian population is deficient in calories and 28 percent in protein (Chand et al. 2003).

Sorghum is a cheap source of energy, protein, iron and zinc next only to pearl millet among

all cereals and pulses (Rao et al. 2006). However, it is popularly grown for feed, fodder and

more recently for bio-fuel purposes in the world.[11]


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In India, sorghum is the fourth most important cereal consumed and cultivated during both

rainy (Kharif) and post-rainy (Rabi) seasons. However, the area under sorghum in India has

declined drastically from 18.6 m ha in 1970 to 7.93 m ha in 2007-08. The total production

also declined from 9.72 m t to 7.78 m t. With emerging cash requirements, farmers

diversified from traditional mono-cropping with sorghum to commercial crops like cotton,

pulses and oilseeds. Both profit motivated and consumption driven factors led to this decline.

Also the growth in productivity varied across the important sorghum growing states. In

contrast, in the recent years, sorghum in rice-fallows in coastal Andhra Pradesh, especially in

Guntur district is gaining popularity among the farmers. It has an average sorghum

productivity of 5.7 t/ha in 2006-07, which is the highest in the country. The farmers are using

inputs especially agrochemicals indiscriminately due to lack of standardized production

technologies for this region. Although they are getting higher yields but the profit margin

could be increased by using cost-effective technologies. Farmers are also not homogenous

with respect to their behaviour in using resources optimally. Under this premises, an attempt

was made to analyze the resource-use efficiency of the sorghum growers and the

requirements in adjustments for optimum utilization of resources for sorghum cultivation in

rice-fallows.

Vermicompost, Phosphate Solubilizing Bacteria (PSB) and free living nitrogen fixing

bacteria are the most widely used biofertilizers significantly contributing N, P and K to plants

and also providing resistance to drought.[12]

However, very limited information is available

regarding the effect of the biofertilizers on the growth and yield of crop plants. In the above

contest the present study was carried out to recommend suitable combination of biofertilizers

application for cultivation of sorghum at commercial level. The present investigation was

under taken with the following objectives.

MATERIALS AND METHODS

Collection of seeds

The seeds of sorghum were obtained from Sri Venkateswara Agriculture Research Institute,

Tirupati, Andhra Pradesh. The seeds of uniform size were separated and surface sterilized

with 0.05% sodium hypo chloride after through washing with tap water before sowing.

Vermicompost

Fresh leafy vegetation was collected from different sites of Sri Venkateswara University

campus at 10 -20 % flowering stage and chopped into the small pieces (2-3 cm). Equal


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amount of weed vegetation was used for each treatment. The material was uniformly spread

into the pits to a height of about 5 cm and sprinkled with 10 percent cow dung slurry (1 kg

dung in 10 liter water) and soil. afterwards the remaining plant material was added and

finally, the pits were sealed with dung slurry and fine clay to prevent loss of heat or exchange

of gases. After partial decomposition (15 days), first turning was given for uniform

decomposition and sufficient amount of water was sprinkled for maintaining 50 - 60 percent

moisture. Then the earthworms of the species Eiseniafoetida and Eudriluseugeniae (50 - 60

individuals per pit) were released. Identification of earthworms was done by [13]

. The

vermicomposting process was completed within 15 days and completely decomposed, fine,

dark brown coloured granular excreta was obtained for the field experiment.

Azotobacter inoculum

Culture of Azotobacter chrocooccum was obtained from Regional Biofertilizers Development

Centre, Bangalore Division, India. From this mother culture carrier based inoculum was

developed by growing it on nitrogen free nutrient broth as described by Ashby for 3 days at

250 C temperature. Then the culture was mixed with lignite powder and this carrier based

inoculum was mixed with soil at the time of planting the test plants.

Composition of medium (Ashby‟s medium) used for growing Azotobacter mother culture

(gm/lit): Mannitol - 20.0, K2HPO4 -0.1, MgSO4.7H2O-0.2, NaCl-0.2, K2SO4-0.1, CaCO3-5.0,

Distilled Water-1000ml with pH – 7.2 at 250 C.

PSB inoculum

Culture of Pseudomonas striata was obtained from Regional Biofertilizers Development

Centre, Bangalore Division, India. P. striatawas inoculated in 500 ml sterilized Pikovskya

broth and incubated at 30o

C for 3 days in a BOD chamber. After obtaining the desirable

growth (107-10

8 cells/ml), the broth was mixed with wood charcoal by maintaining moisture

content at 40 percent and pH 7.0. The slurry thus prepared was mixed with soil at the time of

planting.[14]

Composition of Pikovskaia’s medium

The following constituents were mixed to prepare Pikovskya medium in gr/lit composition.

Ca3PO4 - 5.0, (NH4)2SO4 - 0.5, Dextrose - 10.0, KCl - 0.2, MgSO4.7H2O - 0.1, KCl - 0.2,

Yeast extract - 0.5, MnSO4 – 0.0001, FeSo4 – 0.0001, Agar - 15.0, Distilled water - 1000ml

and pH - 7.0.


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Location of experimental site

The plants were maintained under glass house conditions in the botanical garden of Botany

department, Sri Venkateswara University, Tirupati, Andhra Pradesh, India. The climate was

warm and humid at the time of starting the experiment. The weekly average maximum and

minimum temperatures ranged between 27.1o C to 36.2

o C and 14.6

o C to 23.7

o C

respectively during the experimental period.

Experimental design

T1 : Control (No inoculation)

T2 : Inoculation with vermicompost

T3 : Inoculation with nitrogen fixing bacteria (A. chrocooccum)

T4 : Inoculation with phosphate solubilizing bacteria (P. striata)

T5 : Inoculation with vermicompost and A. chrocooccum

T6 : Inoculation with vermicompost and P. striata

T7 : Inoculation with vermicompost, A. chrocooccum and P. striata

Seedlings

Sorghum plants were grown in plastic pots containing a sterilized mixture of soil and sand

(1/1 w/w). Eight experimental replicates were prepared for each treatment. Seeds of sorghum

were surface sterilized with 0.005% sodium hypocholride for 45 min and rinsed twice with

sterile water and then sown into a 5 cm Depth in pots, grown in a greenhouse under natural

photoperiods (23.5/18°C day/night, 6000/4000 lux light intensity) for three months. Inoculum

of vermicompost (20gm/kg soil), 20 ml of free living N2 fixing bacteria and 20 ml of PSB

was laid around the seed.

Growth parameters

The growth parameters were measured on every 30th

, 60th

and 90th

day of the plant growth in

all the treatments.

Shoot length

The plants were uprooted carefully without damaging the root system. The shoot length of

the plants was measured from the collar region to the tip of the plant, using a standard scale

and values were recorded in centimeters.


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Number of leaves

Number of fully opened leaves in all the treatments was counted manually.

Fresh shoot biomass

The shoot portion was separated from the root system and was blotted on the blotting paper to

absorb the moisture. The weight of the shoot was estimated using an electronic monopan

balance and the values were expressed in grams.

Fresh root biomass

The plants were carefully uprooted and roots were washed in running tap water to clear the

soil particles. The washed roots were blotted on the blotting paper and the roots were

weighed using monopan electronic balance. The values were expressed in grams.

Dry shoot biomass

After measuring the fresh shoot biomass of the plants, it was placed in a paper cover and

dried in a hot air oven at 60o C for 2 days to attain constant weight. Then dry weights of the

shoots were weighed using monopan electronic balance and recorded in grams.

Dry root biomass

To obtain the dry root biomass of the plants, the roots were placed in a paper cover and dried

in a hot air oven at constant temperature of 60o

C, for 48 hours. Then dry weights of the roots

were weighed using monopan electronic balance and recorded in grams.

PHYSIOLOGICAL PARAMETERS

Estimation of chlorophyll content

The chlorophyll content of the plants was estimated in all the treatments on 30th

, 60th

, and 90th

days according to the method of.[15]

The leaves were excised from the plants and washed with

distilled water and blotted dry. One gram of leaf sample was homogenized with 80 % acetone

in a pre-chilled mortar. A pinch of CaCO3 was added to facilitate easy grinding. The extract

was then centrifuged at 5000 rpm for 15 minutes and the supernatant was made up to 10 ml

with 80 % acetone. The supernatant was filtered through Whatmann No. 1 filter paper and

the clear supernatant was transferred to 1 cm glass cuvette. The absorbance was measured

using specific absorptions co-efficient for chlorophyll a and b at 645 nm and 663 nm using 80

% acetone as blank in Shimadzu (UV – 240) double beam spectrophotometer. The following

simultaneous equations were setup for measuring chlorophyll concentrations.


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Chlorophyll „a‟ = (0.0127 x OD at 663 nm)-( 0.00269 x OD at 645 nm).

Chlorophyll „b‟ = (0.0229 x OD at 645 nm)-( 0.00468 x OD at 663 nm).

Estimation of carbohydrates

Carbohydrate fractions such as reducing sugars, non–reducing sugars were extracted from

shoot and root from all the treatments according to the method of[16]

and the content was

estimated on 30, 60 and 90 days of plant growth. 200 mg of oven dry powder was extracted

with 80 % boiled ethanol and was centrifuged at 2000 rpm. The supernatant was reduced to a

volume of 10 ml on boiling water bath and cooled at room temperature. About 5 ml of

saturated neutral lead acetate was added to the alcoholic extract to precipitate proteins. 10 ml

of saturated aqueous disodium phosphate was added to the contents to precipitate excess of

lead. About 300 mg of activated charcoal was added and the contents were shaken at intervals

of 30 minutes and filtered. The filtrate was diluted to 100 ml with distilled water in a

volumetric flask and was used for estimation of reducing and non-reducing sugars.

Estimation of starch

Starch was estimated from the residue left behind the alcoholic extraction of the original

material according to the method of.[17]

The residue was solubilized with 5 ml of 52%

Perchloric acid (PCA) for 30 min, filtered and was made up to 100 ml in a volumetric flask

with distilled water. About 0.2 ml of PCA extract was taken into a test tube to which 2 ml of

distilled water was added. Four ml of freshly prepared and cooled Anthrone reagent was

added to the test tube. The contents were heated for 5 min at 100o C on a water bath and later

cooled to room temperature. The colour intensity of the contents was read at 630 nm using

spectrophotometer.

RESULTS

The results of the experiments carried out on “Effect of Vermicompost, nitrogen fixing

bacteria (A. chrococcum) and Phosphate solubilizing bacteria (pseudomonas straita) on the

growth and biochemical aspects of sorghum” were presented in this chapter.


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10.26 22.75

30.21

13.08 27.87 38.11

15.23 28.5 39.16

15.66 28.75 40.37

17.65 31.12

52.17

18.06 33.87

50.6

22.7

49.87

58.66

0

10

20

30

40

50

60

70

80

90

100

30 days 60 days 90 days

Sh

oot le

ngth

(cm

)

Number of days after treatment

T1

T2

T3

T4

T5

T6

T7

Fig: 1. Effect of vermicompost, Azotobacter and PSB on shoot length of sorghum

Table1: Effect of vermicompost, Azotobacter and PSB on fresh bio mass weight (gm) of

sorghum.

Treat-ments

Shoot fresh biomass Root fresh biomass Total fresh biomass

Days after treatment

30

days

60

days

90

days

30

days

60

days

90

days

30

days

60

days

90

days

T1 0.85 1.46 2.11 0.32 0.71 1.01 1.25 2.25 3.33

(0.03) (0.09) (0.06) (0.05) (0.03) (0.07) (0.06) (0.04) (0.29)

T2 1.73 2.73 3.27 0.65 1.38 1.51 2.39 4.11 4.81

(0.06) (0.10) (0.08) (0.04) (0.05) (0.10) (0.03) (0.24) (0.16)

T3 1.68 2.98 3.41 0.71 1.43 1.61 2.43 4.43 5.06

(0.06) (0.41) (0.19) (0.04) (0.09) (0.09) (0.04) (0.06) (0.11)

T4 1.87 2.95 3.53 0.67 1.48 1.73 2.58 4.44 5.72

(0.21) (0.21) (0.33) (0.02) (0.10) (0.06) (0.08) (0.110 (0.09)

T5 3.73 5.28 6.87 1.42 2.02 2.38 5.15 7.33 9.25

(0.19) (0.32) (0.41) (0.09) (0.08) (0.19) (0.10) (0.21) (0.23)

T6 3.82 5.77 6.91 1.35 2.08 2.68 5.23 7.86 9.59

(0.11) (0.18) (0.19) (0.05) (0.13) (0.11) (0.12) (0.15) (0.58)

T7 5.38 7.75 8.72 2.05 2.88 4.01 7.49 10.83 12.93

(0.28) (0.31) (0.25) (0.08) (0.09) (0.20) (0.15) (0.23) (0.85)

CD 0.063 0.087 0.094 0.031 0.028 0.044 0.079 0.094 0.12

SEM 0.082 0.104 0.073 0.032 0.05 0.019 0.081 0.043 0.054

Values within the brackets indicate standard deviation. Each value represents mean of eight

replications.

Table2: Effect of Vermicompost, Azotobacter and PSB on dry biomass (g) of sorghum.

Treatme-nts

Shoot dry biomass Root dry biomass Total dry biomass

Days after treatment

30

days

60

days

90

days

30

days

60

days

90

days

30

days

60

days

90

days

T1 0.29 0.47 0.71 0.11 0.26 0.44 0.40 0.73 1.19

(0.05) (0.04) (0.08) (0.02) (0.01) (0.02) (0.04) (0.03) (0.04)

T2 0.53 0.94 1.08 0.28 0.43 0.55 0.83 1.35 1.58

(0.04) (0.05) (0.11) (0.03) (0.06) (0.10) (0.03) (0.03) (0.06)

T3 0.57 0.98 1.15 0.30 0.47 0.57 0.90 1.45 2.51


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(0.08) (0.13) (0.11) (0.04) (0.07) (0.03) (0.06) (0.04) (0.05)

T4 0.61 0.93 1.16 0.35 0.46 0.59 0.94 1.38 2.25

(0.07) (0.04) (0.12) (0.04) (0.07) (0.11) (0.05) (0.02) (0.04)

T5 1.26 1.76 1.94 0.58 0.67 0.94 1.84 2.41 2.82

(0.16) (0.18) (0.14) (0.06) (0.07) (0.13) (0.03) (0.32) (0.05)

T6 1.28 1.88 1.92 0.57 0.70 0.91 1.85 2.51 2.69

(0.12) (0.14) (0.13) (0.07) (0.05) (0.15) (0.03 (0.06) (0.03)

T7 1.77 2.58 2.89 0.83 0.98 1.05 2.56 3.25 3.33

(0.14) (0.20) (0.12) (0.10) (0.07) (0.12) (0.02 (0.24) (0.03)

CD 0.022 0.031 0.028 0.015 0.028 0.032 0.041 0.024 0.038

SEM 0.061 0.072 0.053 0.041 0.027 0.038 0.014 0.009 0.012

Values within the brackets indicate standard deviation.

Each value represents mean of eight replications.

3.78

5.75

6.12

4.75

6.87

7.12

4.83

6.75

7.25

5.12 6.22 7.12

5.75 7.07

7.25

5.37

6.89

7.12

6.12 7.27

7.87

0123456789

101112


Nu

mb

er o

f leaves


T1

T2

T3

T4

T5

T6

T7

Fig. 2: Effect of vermicompost, Azotobacter and PSB on leaf number of sorghum.

0.43 0.62 0.78

0.48

0.7

0.89

0.5

0.73

0.99

0.51 0.71

0.95

0.66

0.88 1.09

0.6

0.86 1.05

0.73

1.11 1.32

0

0.5

1

1.5

2


Ch

loro

ph

yll

a (

mg

/g)


T1

T2

T3

T4

T5

T6

T7

Fig 3: Effect of vermicompost, Azotobacter and PSB on chlorophyll contentof sorghum.


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1010.56

1123.07

1402.82

1521.63

1728.12

1841.02

1413.4

1688.22

1802.39

1430.4

1712.62

1863.02

1802.23

2033.82

2233.07

1761.88

2055.21

2192.12

1855.22

2166.42

2302.28

0

500

1000

1500

2000

2500

3000

3500


Non

-red

ucin

g s

uga

rs (

µg/g

)


T1

T2

T3

T4

T5

T6

T7

Fig 4: Effect of Vermicompost, Azotobacter and PSB on shoot non-reducing sugars

content of Sorghum.

302.12

481.41

564.93

383.66 620.73

741.09

359.82 618.11

728.46

370.23 625.86

723.34

506.36

721.63

903.14

484.23 747.29

913.44

568.11

864.32

985.23

0

200

400

600

800

1000

1200

1400


Red

ucin

g s

ug

ars (

µg

/g)


T1

T2

T3

T4

T5

T6

T7

Fig 5: Effect of Vermicompost, Azotobacter and PSB on root reducing sugars content of

Sorghum.

10.88

12.48

18.24

14.01

19.69 27.57

15.03

18.99

26.04

13.51

18.2 23.05

20.17 30.12 38.92

22.05 31.58

37.19

25.35 34.01 41.81

0

10

20

30

40

50

60


Sta

rch

(m

g/g

)


T1

T2

T3

T4

T5

T6

T7

Fig 6: Effect of Vermicompost, Azotobacter and PSB on shoot starch content of

Sorghum.


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Fig 7: T1 Control, T2 vermicompost, T3 nitrogen fixing bacteria (A. chrocooccum), T4

phosphate solubilizing bacteria (P. striata), T5 vermicompost and A. chrocooccum, T6

vermicompost and P. striata, T7 vermicompost, A. chrocooccum and P. striata.

DISCUSSION

To maximize the beneficial plant growth responses, it is important to identify the efficient

strains of PGPRs for the planting situation. It was in this context that efforts were made to

study the plant growth promoting rhizomicroorganisms of sorghum plants with special

reference to vermicompost, nitrogen fixers (Azotobacter chrococumm), phosphate

solubilizers (pseudomonads putida). The results obtained pertaining to this study is discussed

hereunder. The results effect of such an enriched vermicompost and microbial inoculants on

growth, biomass and biochemical aspects of sorghum were studied in pot culture at the glass

house. Supplementing the enriched vermicompost and microbial inoculants to the red soil at

different levels was found to significantly increase the height of the plant, shoot length,

number of leaves, and fresh and dry weight of shoot and root, total fresh and dry matter of the

plant. The vermicompost and microbial inoculants with good amount of plant nutrients has

promoted plant growth.

The plant shoot length was increased significantly with the multiple inoculations compared

with single, dual, triple inoculations and control at 30th

, 60th

and 90th

days after sowing. The

maximum shoot length was recorded in the treatment T7 with22.7, 42.87 and 58.66 cm,

respectively,which received combined inoculation of vermicompost, Azotobacter chroccum,

Pseudomonas putida, which was however on par with treatment T7, which received

combined inoculation of vermicompost, Azotobacter chroccum, and Pseudomonas putida.

The combined inoculations of beneficial organisms have been reported to perform better than


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the single inoculation treatments.[18]

The increase in plant growth in the combined inoculation

treatment of all the inoculants may be ascribed for enhanced N and P nutrient uptake.[19]

However, another mechanism with which it is possible to explain similar effects was the

synthesis and exudation of plant growth promoting substances like IAA and GA.[20]

IAA and

GA are known to enhance the shoot length root length and also the plant growth.[21]

In accordance with the root and shoot growth, the fresh and dry matter content in root and

shoot as well as total dry matter of sorghum plants were also enhanced due to the inoculation

of beneficial organisms. The maximum shoot and root dry weight was recorded in the

treatment T7. Consortia consisting of vermicompost, Azotobacter chroccum, pseudomonas

putida, inoculants increased the root with fresh and dry 5.06 g per plant and shoot fresh and

dry matter of 11.61 g per plant over uninoculated control. Combined inoculations further

enhanced the root and shoot fresh and dry biomass of 16.67 g per plant. Similar results of

increase were reported due to combined inoculation of vermicompost, Azotobacter,

phosphate solubilizers.[22]

Till now, the explanations offered to account for the beneficial action of non-symbiotic

microorganisms on plants have been two fold, first is the nitrogen fixing ability of the

microorganisms and second is the ability of microorganisms to elaborate growth promoting

substances such as vitamins, hormones and amino acids[23-24]

attributed the observed

beneficial response of crop plants to inoculation with A. chroococcum to growth substances

produced by the organisms in addition to the fixed nitrogen made available to the plants.

Chlorophyll content was maximum in the combined inoculation treatment (T7) followed by

T6, T5 at 30, 60 and 90 days after Planting significantly superior over the un inoculated

control, Similar increase in chlorophyll content in several legume crops have been reported

by[25-26]

. The increase in the chlorophyll content attributed can be ascribed to the presence of

rhizomicrobes in the rhizosphere influencing the crop roots to secrete growth promoting

substances, which in turn might have enhanced the growth of N2-fixers, P-solubilizing

organisms in situ and a synergistic effect might have achieved in the treatment, T6 and T7.

Enhancement of rhizomicrobial growth in case of treatment T7 (triple inoculation) might be

due to inoculation of vermicompost and N2-fixers, P-solubilizers (Azotobacter and PSB),

where more root hairs become susceptible for rhizomicrobial infection and also might be due

to better provision for P-availability by P-slubilizers.[27]

Moreover, N-fixers like Azotobacter

and P-solubilizers are known to enhance the plant growth.[28]


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In the present study, vermicompost, Azotobacter and PSB treatment enhanced the plant

growth, quantity of starch and slightly reducing and non-reducing sugars. Increased carbon

fixation, activation of enzymes and increased photosynthetic rate are supposed to be the

possible reasons for increase in starch content.[29]

A similar result was observed by.[30-31]

CONCLUSION

In the present study, the effect of vermicompost, Azotobacter and PSB as single, dual or

mixed inoculum was studied on the growth and physiology of sorghum an important crop

plant. The results revealed that inoculation of vermicompost, Azotobacter and PSB enhanced

the shoot length, fresh and dry biomass of root and shoot, number of leaves compared to

control plants. The contents of chlorophyll, carbohydrates, were also found increased in

treatment plants. The inoculation of vermicompost, Azotobacter and PSB was found superior

than single inoculum not only in promoting plant growth, but also in maintaining soil fertility.

The application of vermicompost, Azotobacter and PSB as bioinoculants in agriculture,

horticulture and other land plants management systems can reduce cost and dependence on

xenobiotics chemicals enhancing our ability to exist in harmony with our living planet.

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