Swidden is an undervalued agroforestry system for the suppression of agricultural weeds: evidence from Tanzania

Abstract Swidden agroforestry remains an important livelihood system for millions of smallholder farmers across the tropics, yet it is increasingly threatened by agricultural intensification and policies promoting more sedentary and commercialised forms of agriculture. Fallowing, a key component of swidden systems, suppresses weeds, restores soil fertility, and provides other ecosystem services. However, the role of weed management in shaping farmer decisions about swidden cultivation and fallowing remains poorly understood. This study investigated how weeds influence farmer decision-making, particularly regarding fallow management, in three villages in Nachingwea District, south-eastern Tanzania. Data were collected through key informant interviews, focus group discussions, transect walks, and crop-budgeting exercises. Farmers identified Striga spp. and several perennial grasses as the most problematic weeds. Among these, Striga was consistently cited as a major factor influencing decisions to initiate fallowing. Farmers regarded fallowing as an effective and low-cost strategy for weed control that simultaneously restored soil fertility and supported crop production. Decisions regarding whether and when to fallow involved balancing these benefits against the costs of foregone production and additional labour requirements. Expenditure on herbicides and other external inputs for staple crops such as maize and pigeon pea was minimal, indicating reliance on labour-based and ecological approaches to weed management. Knowledge of fallowing was transmitted primarily through community networks rather than extension services. These findings highlight the continued importance of swidden agroforestry as a locally adapted system for weed management and livelihood support, while revealing tensions between farmers’ practices and agricultural modernisation policies. Greater recognition of swidden agroforestry within policy and extension programmes could enhance agricultural sustainability and rural livelihoods.