title: NPK NMR Sensor: Online Monitoring of Nitrogen, Phosphorus, and Potassium in Animal Slurry.
abstract: Knowledge of the actual content of nitrogen, phosphorus, and potassium (NPK) in animal slurry is highly important to optimize crop production and avoid environmental pollution when slurry is spread on agricultural fields. Here, we present a mobile, low-field nuclear magnetic resonance (NMR) sensor suitable for online monitoring of the NPK content in animal slurry as an alternative to crude estimates or tedious nonspecific, off-site laboratory analysis. The sensor is based on (14)N, (17)O, (31)P, and (39)K NMR in a digital NMR instrument equipped with a 1.5 T Halbach magnet for direct detection of ammonium N, total P, and K and indirect evaluation of the organic N content, covering all practical components of NPK in animal slurry. In correlation studies, the obtained NMR measurements show good agreement with reference measurements from commercial laboratories.
authors.affiliation: †Center for Insoluble Protein Structures (inSPIN), Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, Aarhus University, Gustav Wieds Vej 14, Aarhus C, DK-8000, Denmark.
authors.forename: Morten K
authors.initials: MK
authors.lastname: Sørensen
authors.affiliation: ‡NanoNord A/S, Skjernvej 4A, Aalborg Ø, DK-9220, Denmark.
authors.forename: Ole
authors.initials: O
authors.lastname: Jensen
authors.affiliation: †Center for Insoluble Protein Structures (inSPIN), Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, Aarhus University, Gustav Wieds Vej 14, Aarhus C, DK-8000, Denmark.
authors.forename: Oleg N
authors.initials: ON
authors.lastname: Bakharev
authors.affiliation: §Department of Engineering, Aarhus University, Hangøvej 2, Aarhus N, DK-8200, Denmark.
authors.forename: Tavs
authors.initials: T
authors.lastname: Nyord
authors.affiliation: †Center for Insoluble Protein Structures (inSPIN), Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, Aarhus University, Gustav Wieds Vej 14, Aarhus C, DK-8000, Denmark.
authors.forename: Niels Chr
authors.initials: NC
authors.lastname: Nielsen
mesh_terms: D000818:Animals; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation*; D009584:Nitrogen / Q000032:analysis*; D010758:Phosphorus / Q000032:analysis*; D011188:Potassium / Q000032:analysis*
chemical_list: D010758:Phosphorus; D009584:Nitrogen; D011188:Potassium