The main pillar of agriculture is the soil because it is both the support and the reservoir of essential nutrients for the plant. The food function it provides for humanity can only be fully fulfilled if it is balanced. Therefore, the development of sustainable agriculture in the world necessarily requires knowledge of the soil. The evaluation of agronomic suitability consists in determining its intrinsic capacity to sustain agricultural productivity over time. Many studies have been conducted in the domain of agricultural land assessment, but the applicability of the methods used in the tropical context requires adaptations that are not always obvious. The new methodological approach we propose for agronomic suitability assessment(AA) was designed and tested in Cameroon (Central Africa) in two pilot sites chosen in two different agro-ecological zones. The sites were the bimodal forest in Bokito which developed on yellow ferralitic soils, and the highland in the Bambouto volcanic massif which had a great pedological variability ranging from red ferralitic soils to andic ferralitic soils and andosols. The approach is inexpensive and based on the combination of four intrinsic soil parameters, namely acidity (pH), useful water reserve (RU), cation exchange capacity (CEC) and erodibility (K); according to the formula: AA = pH × RU × CEC × K. The unit of measurement is the « equivalent hour per mega joule per millimeter (eq.hr. MJ-1mm-1) ». The results showed that the agronomic suitability of the yellow ferralitic soils of Bokito varies from 0.00 to10.53 eq.hr. MJ-1mm-1. On the volcanic massif of Bambouto, the agronomic aptitude varies from 0.00 to 15.70 eq.hr. MJ-1mm-1 on the red ferralitic soils of the lower part of the massif, from 15.70 to 41.84 eq.hr. MJ-1mm-1 on andic ferralitic soils of the middle part of the massif and reaches 108.85 eq.hr. MJ-1mm-1 on the andosols of the summit part of the massif. This work could allow, on the one hand, a better allocation of agricultural land and thus participate in the development of second generation agriculture in sub-Saharan Africa; and on the other hand, contribute to determine more precisely the quality and quantity of fertilizer needed to maintain soil balance. Controlling the use of fertilizers will help to significantly reduce the quantities of chemical elements contained in agricultural products, limit water and soil pollution and thus better preserve human health.

In general, living close to a river is advantage, but there is always of flooding risk, that recurrence in recent decades provokes serious material damage and loss of life. Thus, in order to protect environmental health, economic viability and human activity zones of Mayo-Danay, a careful study of components of natural environment, mainly soil, has proved essential. Clearly, use of GIS in management of natural disasters is most relevant method, designed on integration, Multicriteria Analysis (MCA) and spatial data. Thus, Digital Elevation Model is obtained by manual digitization of contour lines, in order to define the large pedological sets on which wells have been opened, profiles described, soil samples taken and analyzed in laboratory. Main results reveal that soils are sandy to clayey, with neutral and basic pH (7 to 8), high CEC and low organic matter. While, quartz is predominant, associated with smectites, illites, feldspars and iron oxyhydroxides. Updated soil map shows five soil units (1) vertisols with hydromorphic characters (26%), (2) tropical ferruginous soils (32%), (3) less evolved hydromorphic soils (15%), (4) halomorphic vertic soils (9%), and (5) hydromorphic vertic soils (18%). It is an excellent tool for work and research, that responds to agronomic and development problems. It is therefore an excellent tool for work and research, which responds to agronomic and development problems. The multi-criteria spatial analysis establishes hazard and vulnerability, crossing of which gives of flood risk areas map, according to hazard level, very high (12%), high (16%), moderate (14%), low (30%) and very low (28%) risks. For this purpose, it emerges that rainfall is relatively low (700 mm/year), but falls very abruptly during short periods, at high intensity with flows exceeding the infiltration capacities. Morphology of low-slope "yayrés" (280 m) (2‰) is bordered by high landscape (500 to 1400 m) that prevent flow of many rivers that converge into plain. Sandy soils dominated by quartz favor fast rising in water table, while very clayey soils governed by 2/1 clayey (smectites) whose behavior induce waterproofing and intense surface runoff that generate flooding. Evidently, land use change leads to transformation of natural spaces into agricultural and urban environments, which makes soils more compact and impermeable, favorable to flooding. Keywords Soil; Flood risks; Mapping; Mayo-Danay Division; Spatial data DOI: https://doi.org/10.23953/cloud.ijarsg.501

No abstract