<p>Modern agroecosystems increasingly rely on external nutrient inputs to sustain productivity, yet long-term declines in soil organic matter, phosphorus availability, and biological complexity persist across many regions. This Perspective proposes a conceptual reframing of this pattern as nutrient return collapse: a structural failure in which biologically essential matter and organic energy are systematically removed from ecological loops rather than inefficiently managed within them. In natural ecosystems, nutrients and energy are returned to soil through decomposition, sustaining trophic continuity across generations. In contrast, contemporary food logistics, sanitation systems, livestock management, and death practices increasingly divert organic matter into non-reintegrative sinks. Drawing on existing synthesis literature, we identify three interrelated mechanisms through which this structural disconnection undermines soil regeneration: temporal asymmetry between nutrient removal and return that generates cumulative elemental imbalance; cultural and infrastructural arrangements that decouple human and animal biology from ecosystem return pathways; and loss of organic energy inputs that suppress decomposer communities, weakening soil function even where mineral nutrients are supplied. This framing does not reject the short-term necessity of synthetic fertilizers, but argues that long-term agroecosystem stability requires restoring structural return pathways alongside input optimization. Recasting soil degradation as a problem of return failure rather than input insufficiency offers a diagnostic lens for evaluating sustainability strategies across agriculture, waste management, and nutrient recycling.</p>