Fourth Agricultural Science Week of West and Central Africa and 11th

CORAF/WECARD General Assembly

Venue : Niamey, Niger

Date: 16 – 20 Juin 2014

Effect of inoculation with exogenous Bradyrhizobium japonicum strains

and phosphorus application on soybean [Glycine max (L.) Merrill] productivity in two agro-ecological

zones of Benin

Theme

OUTLINE

1- Introduction

2-Methods

3-Results

4-Conclusion

1- INTRODUCTION

Agriculture = base of Beninese economy

Main agricultural constraints in sub-Saharan Africa = constant decrease of soil fertility and inadequacy of cropping systems (Saïdou et al., 2012).

Result = continuous decline in crop yields

To improve crop yields, use of chemical fertilizers whose needs became increasingly important (World Bank, 2008).

risks for the environment (pollution of groundwater) in addition to the expensive cost of manures and the obligation to repeat fertilization

1-INTRODUCTION

Alternative: Crop-livestock integration systems

1- INTRODUCTION

But if animals don’t have a quality diet, they couldn’t produce good dejection for soil fertilization.

Legumes residues are the most beneficial

So, interest of the use of dualpurpose legumes like soybean [Glycine max (L.) Merrill] in crop-livestock integration systems

Soybeans, a major source of inexpensive vegetable protein for human and animal consumption (FAO, 2010)

The fixation of soybean as much as 300 kg of N ha – 1 in addition to the release, in the soil, of nearly 80% for the following crop are current estimate (Hungria et al., 2006).

To improve biological nitrogen fixation, inoculation with efficients strains of soils bacteria like rhizobia is very important (Hussain et al., 2011).

INTRODUCTION

General objective:

to assess if exogenous Bradyrhizobium japonicum strains can improve soybean productivity in Benin.

2- OBJECTIVES

Specific objectives:

(i) to study the effect of exogenous Bradyrhizobium

japonicum strains on yield and yield-related parameters of soybean,

(ii) to determine the main interaction effects of Bradyrhizobium japonicum strains and phosphorus on soybean productivity

(iii) to identify the most effective strain to introduce in crop-livestock integration systems in Benin.

2- OBJECTIVES

3- METHODS

Experimental site: Two Agro-Ecological Zones (AEZ) producers of soybean

3- METHODS

Crop food-producing zone of southern Borgou (Northern Benin: Savè, Glazoué) Climate: soudanian

Annual rainfall: 1100 mm and 1200 mm

Experimental site: Two Agro-Ecological Zones (AEZ) producers of soybean

3- METHODS

Cotton zone of central Benin : Bembérèkè et N’dali

Climate: soudano-guinnean

Annual rainfall: 1000 mm

In both zones, experiments were established in ferruginous degraded soils.

Plant material: One variety of soybeans (TGX 1910-14F)

Microbiological material: Four exogenous strains of Bradyrhizobium japonicum were used for inoculums production:

FA3, STM3043 and STM3045 obtained from Laboratory of Mediterranean and tropical symbiosis of Montpellier (France).

USDA110 from Laboratory of soils Microbiology of Nairobi University (Kenya).

These strains were cultivated in Yeast-Mannitol-Broth medium and were fixed in peat.

3- METHODS

Experimental design: in each zone, split plot with two factors

3- METHODS

T: témoinI1: FA3,I2: STM 3043,I3: STM 3045, I4: USDA 110

Six soybean producers in each zone

Data collection Soil sampling from fields before sowing for

assessement of Soil texture, pH, total carbon, CEC, available P, total Nitrogen etc of soil on surface (0-15 cm)

At flowering time (10 weeks after sowing): nodulation, mycorrhizal colonization, biomass dry weight and nitrogen content

At harvest (4 months after sowing): straw and grain yield

3- METHODS

Statistical analysisAll statistical analysis was carried out using SAS

software version 9.2.

One-way analysis of variance (ANOVA) was performed to determine the statistical differences among the different strains of Bradyrhizobium japonicum. When significant differences (p < 0.05) were noticed, a Student-Newman-Keuls test was used to compare the means

3- METHODS

4- RESULTS

4- RESULTS

Characteristic Central Benin Northern Benin

Sand (%) 81.4 76.2

Silt (%) 8.8 11.0

Clay (%) 8.7 12.2PH (water) 6.4 6.9Total nitrogen (% ) 0.04 0.06

Available P (ppm) 29.8 32.2

Organic carbon (% ) 1.1 1.7Organic matter (% ) 1.8 2.9

Physico-chemical properties of the soil before the starting of the experiment

4- RESULTSEffect of Bradyrhizobium japonicum strains and

phosphorus supply on soybean productivity parameters

  Inoculation

Phosphorus

Inoculation*phosphorus

Nodule number <0,0001*** <0,0001*** 0,0028**

Mycorrhizal colonization <0,0001*** <0,0001*** <0,0001***

Biomass dry weight <0,0001*** <0,0001*** 0,0431*

Nitrogen yield <0,0001*** <0,0001*** 0,0314*

Straw yield <0,0001*** 0,0002*** 0,005 **

Grain yield <0,0001*** <0,0001*** 0,02*

4- RESULTS

Nodule number

Control FA3 STM3043STM3045USDA11005

1015202530354045

e

c cc d

bb

a

b b

Central Benin

0P50P

Nod

ule

num

ber

(num

ber/

plan

t)

100%

Contr

ol FA3

STM30

43

STM30

45

USDA11

005

101520253035

dc c c c

bab

aab

b

Northern Benin

0P50P

Nod

ule

num

ber

(num

ber/

plan

t)

52%

Bars followed by a same letter are not significantly different at p < 0.05 according to Student Newman-Keuls test.

4- RESULTS

Mycorrhizal colonization

Contr

ol FA3

STM30

43

STM30

45

USDA11

00

10203040506070 a

b cb b

b

c d37 35

Central Benin

0P50P

Myc

horiz

atio

n ra

te (

%)

62%

Control FA3 STM3043 STM3045 USDA1100

10

20

30

40

50

60

70a

bc

b bb

cd

c c

Northern Benin

0P50P

Myc

horiz

atio

n ra

te (

%)

65%

Bars followed by a same letter are not significantly different at p < 0.05 according to Student Newman-Keuls test.

4- RESULTS

Shoot dry weight

Control FA3 STM3043 STM3045 USDA1100

5

10

15

20

25

c

b b b bb

aba

a

abCentral Benin

0P50P

Shoo

t dr

y w

eigh

t (g

/pla

nt)

66%

0

5

10

15

20

25

c

bb b bb

a a

ab ab

Northern Benin

0P50P

Shoo

t dr

y w

eigh

t (g

/pla

nt)

62%

Bars followed by a same letter are not significantly different at p < 0.05 according to Student Newman-Keuls test.

4- RESULTS

Biomass aspect and color

4- RESULTS

Nitrogen yield

Contr

ol FA3

STM30

43

STM30

45

USDA11

00

50

100

150

200

250

cb b

b bb

aba ab ab

Central Benin

0P50P

Nitr

ogen

yie

ld (

mg/

plan

t)

165%

Contr

ol FA3

STM30

43

STM30

45

USDA11

00

50100150200250

cb b b b

b

a aab ab

Northern Benin

0P50PSeries3

Nitr

ogen

yie

ld (

mg/

plan

t)

131%

Bars followed by a same letter are not significantly different at p < 0.05 according to Student Newman-Keuls test.

4- RESULTS

Straw yield

Contr

ol FA3

STM30

43

STM30

45

USDA11

00

10002000300040005000

c

b b b bab

aba

ab

Central Benin

0P50P

Stra

w y

ield

(kg

/ha)

0100020003000400050006000

c

ab ab ab abab

aa

ab ab

Northern Benin

0P50P

Stra

w y

ield

(kg

/ha)

Bars followed by a same letter are not significantly different at p < 0.05 according to Student Newman-Keuls test.

75%

71%

4- RESULTS

Grain yield

Control FA3 STM3043STM3045USDA1100

500

1000

1500

2000

2500

3000

c

bb

b b

b

aba

ab abCentral Benin

0P50P

Gra

in y

ield

(kg

/ha)

60%

Contr

ol FA3

STM30

43

STM30

45

USDA11

00

50010001500200025003000

c

bb b

bb

aab ab

ab

Northern Benin

0P50P

Gra

in y

ield

(kg

/ha)

Bars followed by a same letter are not significantly different at p < 0.05 according to Student Newman-Keuls test.

73%

Results obtained showed that inoculation with exogenous Bradyrhizobium japonicum strains and phosphorus supply had improved productivity of soybean in Benin

The best strains were FA3 in Food producing zone of southern Borgou and STM3043 in cotton zone of central Benin

FA3 and STM3043 strains could be used in crop-livestock integration systems for improving soybean productivity and its quality in Benin.

However, phosphorus supplementation could be reduced by a co-inoculation of soybean with Mycorrhizae and Rhizobia.

5- Conclusion

This work was funded by the University of Abomey-Calavi through the project “Programme de Fonds Compétitifs de Recherche ’’

The authors would like to acknowledge the producers and other actors encountered during the study for their valuable and fruitful collaboration.

ACKNOWLEDGMENTS

Thank you for your kind attention