Caractérisation Physico-Chimique des Sols des Vallées Agricoles de la Commune de Ziguinchor au Sénégal

Abstract

Despite the importance of urban agriculture as a strategic axe of resilience to poverty, Ziguinchor's urban agriculture is not well considered by the municipalty autorities and suffers from spatial and soil transformations. The study aims to establish a frame of reference for soil physicochemical characteristics of the agricultural valleys of Ziguinchor's city. For that, 180 soil core samples were collected on the horizon [0-20] cm. They were made up of 12 composite samples analyzed at the Senegal National Pedology Institute. The study showed a predominance of hydromorphic soils with a silty-clay-sandy texture, characterized by a relatively stable structure. Although generally acidic (pH≤ 5) and sodic by location, these soils are relatively rich in OM (0.84%), particularly in the upstream parts of the valleys. The Kandialang-Djibock valley has the most rich soils in OM (1.143%) and a nutrient cation percentage available for crops that exceeds 80%. However, in all valleys, the soils are considered to be very low in N with an interval content [0,10-0.25%], although the C/N ratio is less than 12. Urbanization, silting, acidification and gradual salinization of soils are the main constraints of agricultural production. The solution to these constraints lies in maintaining the fertility and agricultural productivity of these soils, rehabilitating anti-salt dykes and combating the silting of valleys.

Analysis of the effects of climate change on pH and salinity of soil in Bakoum valley watershed (Sedhiou Region/Senegal)

“…Soil pH plays an important role in the availability of nutrients for crops (Dinon and Gerstmans, 2008). This acidification of cropping areas especially at valley level has been raised by several authors (Diallo et al, 2015;Dasylva et al, 2019). It is caused by rainfall deficit, groundwater recharge, sulphide oxidation (Duchaufour, 1983;FAO, 1998).…”

“…It is also the irresponsibility of the beneficiaries. The hydro-agricultural developments that have been carried out in this area have not often met the objective set because of the lack of collaboration of the populations (Dasylva et al, 2019). During the exploratory mission to the Bakoum Valley, the chief of the village of Badiandiang Diola informed that the locks of the structure that regulate the water upstream were stolen by the villagers themselves.…”

Physico-chemical characterization of the soils of the watersheds of Boukombe in North-West Benin

“…Consequently, crop yields and the smooth running of human agropastoral activities are compromised. Soil leaching and the phenomena of drought, rainfall disturbances, shifting and shortening of the rainy season alone weaken the structure and physicochemical composition of soils [20]. Because coarse elements (sand) are dominant in these soils, they are poor reservoirs of water that can be used by plants.…”

“…However, the profound change in the physical properties of the soil can significantly negatively affect soil productivity and hence crop yields. The studies by [20] in the city of Ziguinchor in Senegal, have shown that the splash effect of the intense rains often recorded favors the stripping of the soil, the transport of sandy particles by runoff and silting up of rice fields. A good structure of the topsoil layers is essential in agricultural activities.…”

“…This supports the hypothesis that the nitrogen required for crop growth is due to the biodegradation of soil OM. This dichotomy of OM and nitrogen content, as well as the poverty of soils in phosphorus could be explained by the fact that these nutrients are taken up by crops or by the low abundance of bio-reducers in the environment [20]. Moreover, the fact that the watersheds of the commune of Boukombé are permanently exploited all the rainy seasons is the fundamental reason that the soil samples are taken during the period during which, the crops would have already taken the significant quantity.…”