Smallholders in Tanzania and elsewhere in Africa are increasingly differentiated. This thesis contributes to the empirical and conceptual understanding of the differentiation processes in irrigation by following the internal dynamics among smallholders linked to public investments in improving smallholder initiated small scale irrigation schemes in Kilombero district, Tanzania. The aim of the thesis is to examine the role of public investments in irrigation in transforming rural smallholder farmers and how inclusive these investments are likely to be, specifically, in the current context where policies in irrigation are widely focused on poverty reduction among the smallholders. In this thesis I have used data collected from both irrigating and non-irrigating villages in Kilombero district, Tanzania so as to capture overall transformations in the area and how irrigation contributes to agricultural development and differentiation among smallholders. A combination of methods was used in this thesis, these includes participatory wealth rankings, interviews and walking interviews, focus group discussions, questionnaire survey, and remote sensing data. This thesis consists of four papers and an introductory “kappa”. The study mainly problematizes the general conception within agriculture and irrigation policies that smallholders are homogenous and builds on theories of ‘accumulation from above’ and ‘accumulation from below’ to analyse development and differentiation among the smallholders in irrigation.  In following processes of accumulation among the smallholders, the study links public investments in smallholders’ small-scale irrigation with the processes of ‘accumulation from below’.

Findings of this thesis indicate that public investment in smallholders’ small-scale irrigation builds on pre-existing social differences among the smallholders. In all sub-cases in Kilombero, initial development of irrigation was done by farmers through their own initiatives as a form of a ‘farmer-led’ irrigation development. These developments were mainly traced from the late 1970s to early 1980s, and attracted state investments in lining the canals later in the 1990s onwards. However, it was until the late 1990s to early 2000s where there was increased cultivation in the irrigated areas. The increase went hand in hand with neo-liberalisation of the Tanzanian economy since late 1980s and privatisation of agriculture in the area from 1998. As smallholders were responding to market stimuli and increased productivity in both irrigated and rain-fed cultivation, they became increasingly differentiated. The wealthier farmers were cultivating mostly extensively in relatively larger pieces of land, and the less wealthy farmers were combining cultivation in smaller rain-fed fields and providing labour to other wealthier farmers. Most of the middle wealthy farmers were concentrated in irrigation, and therefore investment in irrigation was clearly benefiting the middle wealthier farmers. The thesis argues that expansion of rice irrigation in Kilombero plays a crucial role in the current agricultural transformations in Kilombero as rice is both a food and commercial crop in the area. In conclusion, the thesis argues that the current investments in smallholders’ small-scale irrigation are fueling processes of ‘accumulation from below’ which are more inclusive as they benefit middle smallholders rather than the large wealthier farmers. These findings points to the importance of focusing on smallholders’ in agriculture and irrigation development for a more inclusive agricultural transformation.