Sustainable Intensification Assessment of Organic Fertilization in Sub-Saharan African Cropping Systems

This thesis examines strategies for achieving sustainable intensification (SI) in Sub-Saharan African (SSA) agriculture through the use of organic and integrated fertilization practices. In a region where declining soil fertility, erratic rainfall, and limited access to external inputs constrain productivity, developing resilient and efficient nutrient management systems is essential to improve food security while safeguarding environmental health. To address these challenges, the research combines quantitative synthesis, simulation modeling, and multidimensional sustainability assessment. A meta-analysis of existing field studies provides a regional overview of fertilizer effects on neglected and underutilized crops, highlighting the agronomic potential of integrated organic-mineral fertilization to enhance yields and nutrient-use efficiency across diverse environments. Complementary long-term crop simulations using the DSSAT-CERES-Maize model explore the interactions between climate variability and fertilization strategies in rainfed maize systems, revealing how temperature and rainfall fluctuations influence productivity and yield stability. Building on these insights, a fuzzy-logic-based framework is employed to evaluate the broader sustainability of fertilization practices through the integration of agronomic, environmental, economic, and social indicators. Together, these approaches form a comprehensive assessment of how different fertilization strategies affect productivity, resilience, and sustainability in smallholder farming systems. The findings demonstrate that integrated nutrient management represents a pragmatic pathway toward sustainable intensification, balancing short-term productivity gains with long-term soil health and socio-economic viability. By bridging empirical evidence, model-based analysis, and participatory assessment, this thesis advances understanding of the mechanisms and trade-offs underlying sustainable intensification in SSA and provides a scientific basis for guiding the design of context-specific, climate-resilient agricultural systems across SSA.