title: Agronomic phosphorus imbalances across the world's croplands.
abstract: Increased phosphorus (P) fertilizer use and livestock production has fundamentally altered the global P cycle. We calculated spatially explicit P balances for cropland soils at 0.5° resolution based on the principal agronomic P inputs and outputs associated with production of 123 crops globally for the year 2000. Although agronomic inputs of P fertilizer (14.2 Tg of P·y(-1)) and manure (9.6 Tg of P·y(-1)) collectively exceeded P removal by harvested crops (12.3 Tg of P·y(-1)) at the global scale, P deficits covered almost 30% of the global cropland area. There was massive variation in the magnitudes of these P imbalances across most regions, particularly Europe and South America. High P fertilizer application relative to crop P use resulted in a greater proportion of the intense P surpluses (>13 kg of P·ha(-1)·y(-1)) globally than manure P application. High P fertilizer application was also typically associated with areas of relatively low P-use efficiency. Although manure was an important driver of P surpluses in some locations with high livestock densities, P deficits were common in areas producing forage crops used as livestock feed. Resolving agronomic P imbalances may be possible with more efficient use of P fertilizers and more effective recycling of manure P. Such reforms are needed to increase global agricultural productivity while maintaining or improving freshwater quality.
authors.affiliation: Department of Natural Resource Sciences, McGill University, Sainte Anne de Bellevue, QC, Canada. graham.macdonald@mcgill.ca
authors.forename: Graham K
authors.initials: GK
authors.lastname: MacDonald
authors.forename: Elena M
authors.initials: EM
authors.lastname: Bennett
authors.forename: Philip A
authors.initials: PA
authors.lastname: Potter
authors.forename: Navin
authors.initials: N
authors.lastname: Ramankutty
mesh_terms: D000383:Agriculture / Q000706:statistics & numerical data*; D003247:Conservation of Natural Resources / Q000379:methods* / Q000706:statistics & numerical data; D018556:Crops, Agricultural / Q000737:chemistry / Q000254:growth & development*; D005308:Fertilizers / Q000032:analysis*; D005843:Geography; D038622:Internationality; D058751:Livestock / Q000502:physiology; D008372:Manure / Q000032:analysis; D010758:Phosphorus / Q000032:analysis*; D012987:Soil / Q000737:chemistry*
chemical_list: D005308:Fertilizers; D008372:Manure; D012987:Soil; D010758:Phosphorus