Phosphorus Stewardship Across Food and Water Systems: Supply Risk, Legacy Phosphorus, and Recovery

Phosphorus (P) is essential for crop production, yet its use still follows a largely linear pathway: phosphate rock is mined, applied to agricultural land, transferred through food and waste systems, and often lost to rivers, lakes, and coastal waters. This review examines how P supply vulnerability, agricultural surpluses and deficits, legacy soil P, eutrophication, climate-sensitive transport, and recovery technologies are connected across food and water systems. A structured narrative review was conducted using Web of Science, Scopus, Google Scholar, and relevant institutional sources. The searches focused on phosphorus fertilizer, legacy P, eutrophication, runoff, wastewater recovery, circular economy, and governance. English-language peer-reviewed studies and high-authority reports, mainly published between 1995 and 2026, were screened for relevance, methodological clarity, and quantitative evidence. A total of 191 records were identified, 115 full texts were assessed, and 101 sources were included. Evidence was grouped into four areas: mineral supply and trade, soil and aquatic P accumulation, recovery from waste streams, and policy. The review shows that concentrated reserves can increase supply risk, but do not alone indicate imminent scarcity. Costs, ore quality, trade, demand, recycling, and technological change also influence P security. Legacy P may support crop uptake while continuing to impair water quality. Recovery technologies such as struvite production and sludge-ash processing offer useful pathways, but their adoption depends on economics, contaminants, regulation, and logistics. Effective P stewardship therefore requires region-specific strategies that reduce losses, improve access and efficiency, manage legacy P, and support practical recovery.