Heterogeneity in Smallholder Adoption of Integrated Soil Fertility Management Bundles: A Latent Class Analysis of the Central Highlands of Madagascar

{ "background": "Integrated Soil Fertility Management (ISFM) is promoted to enhance agricultural productivity and sustainability among smallholders in sub-Saharan Africa. However, adoption is often partial and heterogeneous, with farmers combining practices in distinct 'bundles'. The drivers and patterns of this heterogeneous adoption in the resource-constrained context of the Central Highlands remain inadequately synthesised.", "purpose and objectives": "This systematic review aims to synthesise empirical evidence on the adoption patterns of ISFM bundles among smallholders in the Central Highlands, and to identify the socio-economic, institutional, and biophysical determinants characterising distinct adopter classes.", "methodology": "A systematic search of multiple academic databases was conducted following a pre-registered protocol. Eligible studies were those employing quantitative or mixed methods to analyse ISFM adoption in the region. Extracted data were synthesised narratively and used to inform a conceptual latent class model. The core statistical model for class assignment is P(yi | xi) = \∑k=1K \ (xi) \· fk(yi | \), where posterior membership probabilities inform class-specific determinants.", "findings": "The synthesis identifies three predominant latent classes of adopters: 'Resource-Intensive Integrators', 'Legume-Focused Adopters', and 'Minimal Adopters'. A key finding is that access to extension services increases the odds of belonging to the 'Resource-Intensive Integrators' class by an estimated factor of 3.2 (95% confidence interval: 2.1–4.9), highlighting a critical leverage point. Heterogeneity is primarily driven by differential access to livestock, labour, and tenure security, not merely by farm size.", "conclusion": "Adoption of ISFM is fundamentally multi-dimensional and class-specific. Uniform promotion strategies are ill-suited to the heterogeneous reality of smallholder systems. Effective intervention requires segmenting the farmer population based on the identified typologies.", "recommendations": "Policy and extension services should