The fate of nitrogen of ammonium phosphate fertilizers: A blind spot

Abstract

Abstract Ammonium phosphate fertilizers are a common phosphorus (P) source for crops, namely monoammonium phosphate, diammonium phosphate, and ammonium polyphosphate. Despite containing appreciable nitrogen (N), ammonium phosphate fertilizers are generally considered P fertilizers. However, the approximately 8.5 million Mg N co‐applied with P annually as ammonium phosphate fertilizers represents 8% of global N fertilizer input flux to agroecosystems. Despite this, a systematic review of the literature revealed only one direct assessment of N losses from ammonium phosphate fertilizers. An additional five studies reported NO3‐N leaching and N2O‐N emissions from soils fertilized with ammonium phosphates, but inadvertently as observations from failed or control treatments that are confounded (e.g., not accounting for non‐fertilizer contributions to N losses). The magnitude and fate of N co‐applied with P in ammonium phosphate fertilizers is a blind spot in agroecosystem N budgets and environmental footprints that necessitates quantification.