This project proposes to investigate the resurgence of intentional fallowing as a practice for soil regeneration and as a tool for sustainability policies in Europe. It will deploy an interdisciplinary approach grounded in philosophy and multispecies ethnography to analyse the contemporary resurgence and mutations of intentional fallowing practices in European agriculture and policies, as well as the cultural, social, and scientific consequences of this shift. It combines qualitative research on European farms conducting experimental intentional fallowing, a genealogical analysis of the historical and political context in which these practices are re-emerging, and an exploration of the adjacent spaces in which fallowing and fallowness are studied, such as microbiology, conservation biology, and bioengineering. By combining these three lines of inquiry, the project demonstrates that fallowing is a marginalised practice currently under re-evaluation and potential re-integration into projects and policies that go beyond agricultural concerns. It will analyse the biopolitical and cosmopolitical dimensions of this renewed interest in alternatives to synthetic fertilisers and intensive agriculture by showing that fallowed soils are a site where a variety of interests and projects converge, and by tracing how these practices take up, replay, and extend questions of productivity and idleness, growth and alternatives to economic expansion. This project will combine qualitative methods, in particular in-depth interviews with practitioners in the field, with an extensive engagement with literature in agricultural science, microbiology, conservation biology, and ecology, producing an analysis of fallowing that cuts across what is usually deemed “cultural” and “biological” domains and studies the role, promises, and implications of fallowing practices in times of mass extinction and soil depletion.