Abstract
<title>Abstract</title> <p>Soil fertility decline remains a major constraint to agricultural productivity and resilience in semi-arid sub-Saharan Africa. This study investigated the biophysical and management determinants of soil fertility in mixed crop–livestock systems in Burkina Faso across the Sudan and Sudan-Sahel zones. We combined household surveys of 398 farmers, field measurements from 120 plots, laboratory soil analyses, and gridded climate data (CHIRPS, ERA5-Land, and SMAP). Soil fertility was characterized using key chemical indicators (pH, nitrogen, phosphorus, potassium, and soil organic carbon), together with farm-level tree diversity and nutrient inputs from organic and mineral fertilizers. A multi-group Structural Equation Model (SEM) was applied to identify zone-specific causal pathways. The final model showed excellent fit (CFI = 0.987; TLI = 0.962; SRMR = 0.022) and explained 15.9–18.5% of the variation in soil fertility. In the Sudan zone, climate exerted a strong negative effect on soil fertility (β = −0.436, p = 0.001), while organic and chemical fertilization showed no significant short-term effects. In the drier Sudan–Sahel zone, organic fertilization had a significant negative effect (β = −0.543, p = 0.005), likely reflecting moisture constraints and inefficient manure decomposition. Crop–livestock integration strongly increased organic fertilization in both zones, but this did not translate into improved soil fertility outcomes. Overall, the results demonstrate that livestock presence alone does not enhance soil fertility; improvements depend on manure quality, decomposition conditions, and context-specific management. Zone-tailored strategies are therefore required, including erosion control in the Sudan zone and improved composting and integrated nutrient management in the Sudan-Sahel, to strengthen soil fertility resilience and food security in semi-arid mixed farming systems.</p>