Impacts of land cover changes on soil quality and the distribution/composition of pasture grasses species in Enkushin Micro Catchment, Kajiado County, Kenya

Land cover changes have profound effects on production systems in arid and semi-arid lands (ASALS). Often these changes results in land degradation in form of soil erosion and overgrazing of pastures. This study evaluated the impact of land cover changes in Enkushin micro-catchment in Kajiado for a period of 25 years (1993 to 2018) on soil quality indicators and the composition and distribution of pasture grasses species. A stratified random sampling was carried out using geographical information system (GIS) and remote sensing tools for different land cover classes of the area. Soil samples were collected at 0-25 cm, 25-50 cm and 50-75 cm depth from six land cover classes: wooded bushed grassland (WBG), riverine woodland (RW), bushed grassland (BG), wooded bush land (WB), wooded dense bush land (WDB) and bush land (B). These samples were analyzed for soil quality indicators; pH, bulk density (BD), saturated hydraulic conductivity (HC), total organic carbon (TOC), texture, cation exchange capacity (CEC), and for composition and distribution of grass species using soil seed bank germination method of soil samples at 0-5 cm depth. Data obtained were analyzed using XLSTAT 2018 version for ANOVA and frequency of occurrence in different land cover classes. Results showed significant difference in CEC, BD, increase in silt/clay ratio indicating soil erosion, reduction of soil organic carbon stocks and dominance of grasses associated with degraded pasture lands (Eragrostis Tremula and Sporoborus grasses spp.) in most of the land cover classes. We conclude that current pasture management and stocking density is not sustainable. And mitigation measures such as ex closure and reseeding are needed to restore the degraded lands.