Proceeding from land degradation and soil fertility decline in sub-Saharan African smallholder agriculture and drawing on empirical research with smallholder farmers in Tororo district in south-eastern Uganda (2010-2012), this thesis identifies local collective strategies in response to changing livelihood conditions. In an attempt to coproduce knowledge with a transformative potential, the thesis also illustrates how action research can be employed to envision, implement and evaluate a locally anchored practice to improve soil fertility, namely the use of human urine as a crop fertilizer. The research shows that effective responses to land degradation must acknowledge the multiple stressors of smallholder farming and thus go beyond current technocratic and managerial approaches. To do this, soil fertility decline is best understood as a socially, politically and agro-ecologically integrated issue. Collective action mediated by farmer groups, in which women in particular engage, can be a significant response to everyday constraints and vulnerabilities, not only for overcoming barriers that may obstruct individual coping strategies but also for enhancing farmers’ capacities to manage land sustainably. However, findings also indicate that collective action is no universal remedy; the ability to participate in and benefit from collective action is socially differentiated and numerous structural barriers limit the type of change that can be achieved through local self-organisation. In support of sustainability science and sustainability alike, the thesis makes three contributions to ways of ‘thinking and doing’ political ecology: by engaging critically with narratives on land degradation; by advancing understandings of the merits and limits of collective action in the context of rural livelihoods; and by providing insights on solutions-oriented research.