This thesis examines the current agricultural reuse, and promotes the expanded future use, of soil amendments derived from human excreta through a case study among smallholder farmers in South India and a practical manual intended to serve development practitioners working in sanitation and agriculture. In the first chapter, I use qualitative methods (semi-structured interviews and participant observation) to evaluate the factors facilitating and forming barriers to the use of human feces compost by smallholder farmers in Tamil Nadu, India. In the second chapter, I synthesize existing literature related to smallholder soil fertility nutrient management and ecological sanitation to guide sanitation and agricultural development practitioners through the process of integrating agricultural considerations into new ecological sanitation projects, positioning excreta-derived fertilizers as a novel means of improving smallholder soil fertility management.