Soil Mapping and Assessment of the Agricultural Capacity of the Land at Kouh-Est in the Logone Oriental (Southern Chad)

Abstract

Agriculture is the main source of income and survival for the population of East Kouh. Population growth has led to an increase in arable land, a reduction in fallow periods and migration in search of arable land, with the corollary of soil degradation. So understanding the spatial distribution of surface conditions through mapping and knowing the agricultural capacity of the land are essential challenges for the ecosystem services they provide. However, the department of Kouh-Est does not yet have an exhaustive geographical coverage of soil properties that will enable them to be used wisely in the long term. The aim of the study is to understand the surface condition of Kouh-Est’s soils and assess their fertility levels. Remote sensing and geographic information systems have revealed that the terrain is relatively flat and gradually rising, the hydrographic network converges from the outside towards the centre, and three types of soil have been identified, including ferrallitic soils, ferruginous soils and alluvial soils. Bare soil occupies a large part of the study area (50.92%), the high plateaux are reserved for agriculture (32.21%) and, finally, vegetation, water and forest occupy a tiny, predominantly low-lying area (17.02%). Soil fertility indices and nutrient ratios were used to assess the level of fertility of the various soils in the study area. These parameters range from 0.7 < ISS < 17.27; 8.33 < IF < 704; 0.16 < L/A < 1.53; 3.94 < C/N < 1912.83; 0 < NT/pH < 0.02; 11.02 < S/T < 116.29; 0 < N/P < 2.5; 0 < C/P < 66; 0.75 < Ca/Mg < 9.26; 0.16 < Mg/K < 184; CEC/A ≤ 0.41. Four soil fertility classes are identified. The physical parameters of the soil are acceptable, but there are shortcomings in terms of chemical fertility. Organic and mineral amendments are essential to improve soil fertility.