Impact of climate change and land use/land cover change on soil fertility in the cotton Basins of Côte d’Ivoire

Abstract

The study assessed the impact of alterations in land use and land cover, as well as fluctuations in climate patterns, on soil fertility within the cotton-producing area of Côte d'Ivoire. The study entails evaluating how farmers perceive and cope with climate change, determining the current state of soil fertility, evaluating land suitability and management options for cotton production, and simulating the way the land in the region will be utilized and the vegetation that will cover it in the future. To evaluate smallholder farmers' perceptions of climate change adaptation options, a structured questionnaire with closed questions was used to collect data from 355 farmers located in the cotton basin of Côte d'Ivoire. The findings revealed that most respondents acknowledged the existence of climate change in the area and its detrimental impact on farmers' livelihoods, leading them to adopt coping mechanisms. To determine the status of soil fertility, the study analyzed 64 soil samples collected in 2013 and 2021 in the same fields where cotton was grown. Specifically, the analysis focused on the physical and chemical properties of the topsoil layer, ranging from 0 to 20 centimeters in depth. Between 2013 and 2021, the chemical properties of the soil (concentrations of Ca2+, Mg2+, K+, and Base Saturation (BS)) saw only a slight improvement, leaving soil fertility as a significant constraint on cotton production. Targeted, site-specific soil management is necessary to address this issue. The study evaluated soil suitability for cotton cultivation in eight villages in the Côte d'Ivoire cotton basin by characterizing two representative soil profiles (0-100 cm) per village which were described in terms of their soil chemical and physical properties. The soils were "moderately suitable" (S2) or "marginally suitable" (S3) due to poor chemical properties, such as the Sum of Basic Cations (SBC) and organic carbon (OC). The study also used Landsat images to track changes in land use and land cover (LULC) between 1998 and 2020 and predicted future LULC for 2035 and 2063 using the TerrSet software and the CA-Markov chain. From 1998 to 2020, there was a reduction in the share of forestland and Savannah with each zone decreased by -11.09 % and -21.56 % respectively at Korhogo, -14.09 % and -1.78 % respectively at Ferkessedougou, -0.33 %, and -14.8 % respectively at Boundiali, and -6.9 % and -31.33 % respectively at Mankono, while water body, cropland, and settlement/bare land increased. From 1998 to 2035, the results revealed that the share of cropland and, settlement/bare land within the department continue to increase in the study area by 4.54 % and 28.2 %, respectively at Korhogo, 5.34 %, and 10.45 % at Ferkessedougou, 14.95 %, and 0.01 % at Boundiali, and 1.12 %, and 37.04 % in the zone at Mankono. From 1998 to 2063, the results revealed that the share of cropland and, settlement/bear with the department's land could continue to increase. The findings of this study could aid in improving and optimizing soil management practices within the cotton-producing region of Côte d'Ivoire.