Abstract
Background:
Agriculture remains central to Nigeria’s economy; however, despite its importance as a major vegetable crop, onion productivity in the country continues to lag behind global benchmarks.

Aim:
This study analyzes the determinants and interdependence of the adoption of multiple sustainable agricultural practices (SAPs) by smallholder onion farmers in the Wamakko Local Government Area.

Methods:
A multistage sampling procedure was employed to select 162 onion farmers. Data were obtained through structured questionnaires administered via face-to-face interviews. Data were analyzed using descriptive statistics, an adoption index, and a multivariate probit (MVP) model. A multivariate probit (MVP) model was employed to account for the possibility that farmers simultaneously adopt multiple sustainable agricultural practices and that these decisions are interdependent.

Results:
The results show that onion farmers are predominantly within their economically active age group, indicating a strong potential for improved agricultural practices to be adopted. The adoption pattern further reveals that sustainable agricultural practices are implemented jointly rather than independently, suggesting that practices are complementary. The multivariate probit estimates indicate that the adoption determinants vary across practices. Age negatively influences the adoption of Organic Farming (OF) but positively affects reduced tillage. Household size is positively associated with the adoption of Integrated Weed Management (IWM), while education significantly increases the likelihood of adopting IWM. Farming experience positively influences Crop Rotation (CR) but negatively affects Reduced Tillage (RT). In addition, farm size shows a negative relationship with IWM, and total onion output is negatively associated with organic farming. These findings suggest that both human capital and resource endowment play an important role in influencing farmers’ adoption decisions, although their effects differ across practices. The model’s joint significance confirms the relevance of the explanatory variables, while the multivariate framework captures the interdependence of adoption decisions. However, these relationships should be interpreted as associations rather than causal effects.

Conclusion:
The study concludes that farmer characteristics and the interrelated nature of SAPs strongly shape adoption patterns. It recommends strengthening extension services, improving access to inputs and credit, enhancing farmer education, and promoting youth participation to increase SAP adoption and narrow the onion production productivity gap.

Key words: Adoption behavior; Determinants; Nigeria; Onion production; Smallholder farmers.