title: Phosphorus in manure and sewage sludge more recyclable than in soluble inorganic fertilizer.
abstract: Phosphorus (P) flow from deposits through agriculture to waterways leads to eutrophication and depletion of P reserves. Therefore, P must be recycled. Low and unpredictable plant availability of P in residues is considered to be a limiting factor for recycling. We identified the determinants for the plant-availability of P in agrifood residues. We quantified P in Italian ryegrass (Lolium multiflorum) and in field soil fractions with different plant availabilities of P as a response to manure and sewage sludge with a range of P capture and hygienization treatments. P was more available in manure and in sludge, when it was captured biologically or with a moderate iron (Fe)/P (1.6), than in NPK. Increasing rate of sludge impaired P recovery and high Fe/P (9.8) prevented it. Anaerobic digestion (AD) reduced plant-availability at relevant rates. The recovery of P was increased in AD manure via composting and in AD sludge via combined acid and oxidizer. P was not available to plants in the sludge hygienized with a high calcium/P. Contrary to assumed knowledge, the recyclability of P in appropriately treated residues can be better than in NPK. The prevention of P sorption in soil by organic substances in fertilizers critically enhances the recyclability of P.
authors.affiliation: Natural Resources Institute Finland , Jokiniemenkuja 1, FI-01300 Vantaa, Finland.
authors.forename: H
authors.initials: H
authors.lastname: Kahiluoto
authors.forename: M
authors.initials: M
authors.lastname: Kuisma
authors.forename: E
authors.initials: E
authors.lastname: Ketoja
authors.forename: T
authors.initials: T
authors.lastname: Salo
authors.forename: J
authors.initials: J
authors.lastname: Heikkinen
mesh_terms: D000383:Agriculture; D005308:Fertilizers / Q000032:analysis*; D008129:Lolium / Q000737:chemistry* / Q000254:growth & development; D008372:Manure / Q000032:analysis*; D008962:Models, Theoretical; D010758:Phosphorus / Q000032:analysis* / Q000737:chemistry; D012722:Sewage / Q000737:chemistry*; D012987:Soil / Q000737:chemistry; D012995:Solubility
chemical_list: D005308:Fertilizers; D008372:Manure; D012722:Sewage; D012987:Soil; D010758:Phosphorus