The objective of this research was to study the relationships between soil characteristics and land use on resulting weed vegetation in order to find the most effective factors in the separation of weed species and morphological types in Southern Guinea Savannah of Nigeria. The assumption that ‘soils’ and ‘vegetation’ are closely associated was tested by describing soils along the University of Ilorin Teaching and Research Farm catena, Ilorin (located approx. on latitude 80 29’N, longitude 40 35’E on an elevation of 310m above sea level, and with an average annual rainfall of 1000 – 1240mm). There were 3 plots representing soil types on which soil profiles pits were dug for physical and chemical analysis of the soils and classification of the pedon. Two land use types (cropped and non-cropped) represented the fields which were identified within each plot from which vegetative sampling was done. The ‘Soils’ were considered at two levels: soil type classification  and soil properties (physical and chemical). ‘Vegetation’ was considered in three ways: species, morphology and life cycle. Richness and similarity indices showed that some weed species were common to more than one soil and land use types while others were exclusive in their existence. Results showed that weed vegetation distribution patterns were mainly related to soil characteristics such as texture, sodium, magnesium, soluble potassium, nitrogen content and land use type. The variations in weed composition and abundance in each sampled plot might have resulted from cultural practices, environmental sieve and local soil properties and conditions.
Keywords: Weed; soil; land use; vegetation.