Abstract
<title>Abstract</title> <p> Physiographic variation influences soil hydro-environmental conditions and associated biogeochemical processes, yet its role in regulating poultry-manure-based compost-induced soil biochemical responses in tropical savanna soils remains poorly understood. This study investigated how physiographic position modulates compost-induced changes in soil moisture, estimated redox potential (Eh), microbial frequency of occurrence, enzyme activities, nutrient uptake, and vegetative growth of okra ( <italic>Abelmoschus esculentus</italic> L.) in a southern Guinea savanna soil. A 3 × 2 factorial screenhouse experiment comprising three physiographic positions (crest, backslope, and toeslope) and two compost levels (0 and 20 t ha <sup>-1</sup> ) arranged in a completely randomised design with three replications was conducted over eight weeks. The compost was produced through aerobic decomposition for 12 weeks before application. Compared with the unamended control, compost amendment significantly increased soil moisture, cellulase and protease activities, nutrient uptake, and vegetative growth across all physiographic positions (P ≤ 0.05). Soil moisture consistently followed the order toeslope > backslope > crest, whereas moisture-derived estimates of Eh exhibited an inverse trend. At 8 WAP, enzyme activities were highest in compost-amended toeslope soils and were positively associated with soil moisture, nutrient uptake, and growth variables. In contrast, fungal and bacterial frequencies displayed weak relationships with enzyme activities and plant performance. Compost application increased nitrogen, phosphorus, and potassium uptake by 28-36%, resulting in improved plant height, stem girth, leaf production, leaf area, and leaf area index. These findings suggest that landscape position influences the agronomic effectiveness of poultry-manure compost through differences in soil moisture availability and associated biochemical processes, highlighting the need for site-specific organic amendment strategies in tropical agroecosystems. </p>