Potential of Biostimulants Based on PGPR Rhizobacteria Native to Benin’s Soils on the Growth and Yield of Maize (<i>Zea mays </i>L.) under Greenhouse Conditions

The application of biostimulants in agriculture represents an environmentally friendly alternative while increasing agricultural production. The aims of the study were to develop solid biostimulants based on five rhizobacteria native to Benin’s soils and to evaluate their efficacy on the growth and biomass yield of maize under greenhouse conditions on ferrallitic and ferruginous soils. Clay and peat were used as a conservation binder for the preparation of the biostimulants. These binders were used alone or combined in the different formulations with maize flour and sucrose. 10 g of biostimulants were applied at sowing in pots containing five kilograms of sterilised soil. The experimental design was a completely randomised block of 24 treatments with three replicates. The results obtained showed significant improvements (P < 0.001) in height (49.49%), stem diameter (32.7%), leaf area (66.10%), above-ground biomass (97.12%) and below-ground biomass (53.98%) on ferrallitic soil with the application of the clay + Pseudomonas putida biostimulant compared to the control. On the other hand, the use of the peat biostimulant + Pseudomonas syringae was more beneficial for plant growth on ferruginous soil. The height, stem diameter, leaf area, above-ground biomass and below-ground biomass of the plants under the influence of this biostimulant were improved by 83.06%, 44.57%, 102.94%, 86.84% and 42.68%, respectively, compared to the control. Therefore, these results confirm that Rhizobacteria express their potential through biostimulants formulated on maize. The formulated biostimulants can later be used by producers to improve crop productivity for sustainable agriculture.

Modelling the Current and Future Spatial Distribution Area of Shea Tree (<i>Vittelaria paradoxa</i>C. F. Gaertn) in the Context of Climate Change in Benin

In Benin, Shea tree (Vitellaria paradoxa) is one of the agroforestry species of great socio-economic importance for local populations. Given the actual variation in the climate parameters, it is necessary to anticipate the future spatial distribution of Shea trees as an adaptation strategy and for designing relevant conservation strategies. The aim of the present research was to evaluate the influence of climate change on the distribution areas of Shea trees in Benin. Occurrence data consisting of geographic coordinates of Shea trees in Benin as well as bioclimatic variables were recorded. Furthemore, additional presence points were collected from the Global Biodiversity Information Facility database website. Current and future environmental data for the study area were obtained from the Africlim website. Bioclimatic variables (moisture and temperature), monthly maximum and minimum temperatures and annual rainfall were collected from Worldclim synoptic stations website for the period 1970-2000. The aridity index was created from the potential evapotranspiration (PET) and annual rainfall, using spatial analysis tools of ArcGIS. The impact of current and future environmental conditions on favourable Shea trees’ growing area was assessed following the maximum entropy (MaxEnt) approach under two climate scenarios (RCP 4.5 and RCP 8.5). Under the current climate conditions, 80% of Benin territory and 79% of the protected areas were highly favourable for Shea trees growing and conservation. However, all climate scenarios projected the significant decrease of 14% to 19% of the distribution of favourable for Shea tree growing area and 26% to 30% of the protected areas by 2055 in favour of non-favourable for the trees’ distribution. The protection of habitats favourable for the species development, coupled with a quick restoration of the species through the use of appropriate vegetative propagation techniques are required to sustain the species’ conservation in Benin and maintain farmers’ livelihood.

Structural and Mineralogical Characterization of the Clayey Deposits of Gbédji-Kotovi in Lama Depression, Bénin

The objective of the study was to characterize the clays of the Lama depression in Benin. Macroscopic examination of hand soundings, dynamic penetration test and stratigraphic correlation of water borehole logs, as well as scanning electron microscopy (SEM) combined with energy-dispersive X-ray microanalysis (EDX) method were made on compact or stratified clays. The large grains are embedded in a sintered matrix. The texture is heterogeneous and open, including quartz, carbonates and organic matter. The fine fraction is dominated by mineral paragenesis characterizing Kaolinite-Quartz-Calcite-Gypsum dioctahedral smectites composed of: Oxygen, Silica, Carbon, Aluminum, Iron, Zinc, Titanium and Magnesium. This smectic and regular structure includes coarse grains of the order of 800 μm. The pore diameters vary from 130 μm to 1.14 μm. The inter-particle porosity is poorly developed unlike the inter-aggregate pores larger than 0.05 μm. The texture is laminar and shows elongated turbo static particles with more or less rounded edges and honeycomb particles. Quartz and carbonates induce an increase in heterogeneities which develop mechanical sensitivity and hydraulic conductivity. High contents of silica, iron or aluminum and low contents of calcium and magnesium, as well as the presence of other trace elements suggest an alumino-ferriferous clay resulting from the hydrothermal alteration of the acid granite massif. These heterogeneities promote less tortuous pores or paths, making these clays more permeable. Finally, other stabilization studies and improvements to hydraulic products and binders should favor the use of the studied clay as improved backfill or drilling muds.