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 e ﬀ ect of exogenous Bradyrhizobium japonicum strains on yield and yield-related parameters of soybean, (ii) to determine the main interaction e ﬀ ects 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
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 F) 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: témoin I1: 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 analysis All 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
CharacteristicCentral BeninNorthern Benin Sand (%) Silt (%) Clay (%) PH (water) Total nitrogen (% ) Available P (ppm) Organic carbon (% ) Organic matter (% ) Physico-chemical properties of the soil before the starting of the experiment
4- RESULTS Nodule number Bars followed by a same letter are not significantly different at p < 0.05 according to Student Newman-Keuls test.
4- RESULTS Mycorrhizal colonization 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 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 Bars followed by a same letter are not significantly different at p < 0.05 according to Student Newman-Keuls test.
4- RESULTS Straw yield 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 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