Relationship Between Soil Physicochemical Properties and Weed Abundance Along Topographic Gradients in Niger State, Nigeria

Abstract

The relationship between soil properties and weed distribution across two geological formations were evaluated on morphological, physical, and chemical properties, and their influence on weed distribution along two toposequences in different geological formations, Minna (Basement Complex) and Bida (sedimentary formation) in Niger State.. Six soil profile pits were excavated across the two toposequence three from each toposequence at upper, middle, and lower slope positions, and samples were collected from identified genetic horizons for laboratory analyses using standard procedures. Weed assessment was conducted using 1 m² quadrants, and species were identified using standard taxonomic guides. The results showed that soils across the two toposequences were predominantly loamy sand, with sand content ranging from 800–840 g kg⁻¹, indicating coarse texture. The soil structure varied from weak granular in surface horizons to moderate subangular blocky in subsoils. The soil pH ranged from slightly acidic to near neutral (6.00–6.91) in the two toposequence, while organic carbon and total nitrogen decreased with depth, indicating surface accumulation of organic matter. Exchangeable bases were moderate, suggesting a moderate fertility status. Lower slope positions exhibited relatively higher organic matter and nutrient accumulation due to erosion–deposition processes. Weed distribution varied markedly across slope positions, with drought-tolerant species dominating the upper slopes and moisture-loving species prevalent on the lower slopes, particularly under Basement Complex soils. The study demonstrates that topography and parent material jointly influence soil variability and weed distribution. These findings highlight the importance of site-specific soil and weed management strategies for improved and sustainable agricultural productivity.