TERRACE ADOPTION AND ITS ROLE IN SOIL ORGANIC CARBON DYNAMICS IN AGROPASTORAL WESTPOKOT COUNTY, KENYA

Abstract

Drylands of West Pokot experience severe soil erosion that has affected the community’s livelihood and socio-economic dynamics. The severity of erosion in the region is sustained by vulnerable soils and human activities that trigger scarce vegetation cover and low biodiversity. Among the conservation measures adopted in the area, terraces have the potential to accelerate the restoration process. However, insufficient information on terrace adoption factors and benefits limits scaling. This study identified factors that influence the adoption of Fanya Juu and Fanya Chini terraces and assessed their impact on soil organic carbon dynamics in common land use systems in Chepareria, West Pokot County. The study was conducted in two phases, aiming to (1) establish agropastoral socio-cultural factors that influence residents of dryland Chepareria region to adopt soil conservation measures, with particular interest on Fanya Juu and Fanya Chini, and (2) delve into assessing how adoption of terraces influences ecosystem recovery by using soil organic carbon dynamics as an indicator. Socio-cultural data were collected through self-administered semi-structured questionnaires, focus group discussions, cross-sectional field measurements, and observation of existing terrace characteristics. To examine the influence of terraces on SOC dynamics, soils were sampled in Arenic Lixisols, which dominates lowland parts of Chepareria, where the study was conducted. The experiment evaluated the influence of integrating the two terraces in common land uses in the region, which includes maize-beans intercrop and pastures, on soil organic carbon dynamics. Results indicate that Chepareria residents are aware of the ongoing soil erosion at farm and landscape levels. Community-driven approaches, gender, size of land, and topography are key factors contributing to adopting soil and water conservation practices. Results on the influence of terraces on SOC dynamics established persistent high TOC (13 g C kg-1) in pasturelands with terraces. In comparison, degraded land with no intervention was found to have the lowest TOC (6.0 g C kg-1). Terraced farms with longer residence time (> 4 years old) had significantly higher organic carbon than (<4 years old). Other soil properties remained stable with terrace age (1-5 years). Labile SOC and non-labile SOC differed significantly within and across land use types with or without terraces (p<0.05). Pasture and crop systems with terraces were found to have high labile SOC content of 5.9 g C kg-1 and 7.2 g C kg-1, respectively. Labile SOC increased from 1 year old to 5 years after construction. Combined pasture and terraces had a significantly high carbon management index (CMI) of 161.7, with the least amount found in degraded lands. The weighted enrichment ratio (WER) decreased with the time the terraces had stayed in the system, indicating stabilization of the land use system and evidence of reduced on-farm resource leakages. In conclusion, land degradation is a significant challenge acknowledged by the locals of West Pokot. Terracing restores the ecosystem functions as observed in the improved SOC dynamics of LUTs with Fanya Juu and Fanya Chini. However, terraces should be introduced to highly disturbed systems like croplands, which also have high SOC changes.