Soil Characteristics and Pedoclimatic Evaluation of Rainfed Sorghum (Sorghum bicolor (L.) Moench) in the Mayo-Lemié Division, South-Western Chad

Abstract

In recent decades, many regions in the Chad Republic in Central Africa have experienced a continuous decline in agricultural yields. In order to determine the main factors leading to this decline in yields and mainly Sorghum yields, this study was conducted in South-Western Chad, in the Sudano-Sahelian environment. Three soil profiles of variable depths, namely, M1, M2, and M3, were dug along a toposequence, respectively, in the footslope, mid-slope, and the upslope. Soil samples collected from each horizon in the three soil profiles were labelled and sent to laboratories for mineralogical, geochemical, and physicochemical analyses. For land evaluation, climatic characteristics are divided into rating groups with respect to the crop and its climatic requirements. Parametric values were attributed to each soil characteristic for soil evaluation and the land index calculated. The main minerals identified in the studied soils are quartz, K-feldspars, plagioclase, kaolinite, smectite, illite, associated to traces of anatase, sepiolite, calcite, and interstratified minerals. In all the analyzed samples, silicon content is very high. It is closely followed by aluminum, iron, and potassium. The presence of kaolinite and smectite suggests that monosiallitisation is a crystallochemical processes acting at the bottom of profile towards bisiallitisation. All samples collected from the three soil profile horizons are mainly sandy and globally poor in nutrients. The pedoclimatic assessment of Sorghum cultivation reveals that the studied soils are marginally to moderately suitable for the production of Sorghum due to soil texture, wetness, and soil fertility. The decline in yields is related to low base saturation, in line with low exchange base content in the studied soils. These limitations could be solved by restoration of the cation balance through fertilization and liming, combining organic inputs with mineral fertilizer, and the realization of channels for the drainage of water at the base of the soil sequence.