Terminology for residual and legacy phosphorus

Abstract

Phosphorus accumulation in agricultural soils is a growing concern worldwide, but terminology on this issue is confusing. The accumulated phosphorus is often described as residual phosphorus. However, agronomists use this term for the fertilizer not taken up by the crop, and soil scientists use it to describe the phosphorus remaining in soil after sequential extraction, a procedure used to characterize the chemical nature of soil phosphorus. These different uses of residual phosphorus are mutually incompatible because phosphorus accumulated in the soil is often readily soluble, while phosphorus remaining after sequential extraction is extremely stable. To resolve this, we endorse the term legacy phosphorus to describe the phosphorus accumulated in soil through human activity, based on the definition of legacy as something received from the past or carried over from past actions. This allows the term residual phosphorus to be reserved for the unextractable phosphorus in sequential extraction schemes (i.e., in the residue, leftover or remaining). Finally, we recommend the term surplus phosphorus for the fertilizer not taken up by the crop, based on the definition of surplus as an excess of supply over demand. This clarification of terminology will reduce confusion as research progresses on this interdisciplinary topic.