Origin, Impact, and Management of Legacy Soil Phosphorus

Phosphorus (P) inputs are essential for increasing and maintaining global agroecosystem productivity. However, concerns persist over the long-term availability and rising cost of the P needed to sustain future food production. Most soils have a high P retention (fixation) capacity, limiting P availability and use efficiency (often <50%), and leading to the accumulation of residual P in soil (i.e. legacy soil P). Over time, this legacy P contributes to water eutrophication through diffuse losses via runoff and leaching. Despite its environmental risks, legacy soil P represents a significant resource that could be partially mobilized to reduce the need for new P inputs while maintaining productivity. However, its availability to plants depends on soil properties, environmental conditions, crop species, and management practices. Management options designed to lower accumulation and increase mobilization of legacy soil P include avoiding excess P inputs, replacing conventional water-soluble fertilizers with sparingly soluble alternatives (e.g. reactive phosphate rock, struvite), integration of P-efficient plant species into crop rotations (e.g. green manures), and optimizing biological processes known to improve P use efficiency by plants (e.g. mycorrhizae inoculation). Information © The Authors 2025