title: Nitrification in a zeoponic substrate.
abstract: Clinoptilolite is a zeolite mineral with high cation exchange capacity used in zeoponic substrates that have been proposed as a solid medium for growing plants or as a fertilizer material. The kinetics of nitrification has not been measured for NH4+ saturated zeoponic substrate. Experiments were conducted to evaluate the production of NO2- and NO3-, and nitrifier populations in zeoponic substrates. Small columns were filled with zeoponic substrate inoculated with a commercial inoculum or soil enrichment culture of nitrifying bacteria. In addition to column studies, a growth chamber study was conducted to evaluate the kinetics of nitrification in zeoponic substrates used to grow radishes (Raphanus sativus L.). The zeoponic substrate provided a readily available source of NH4+, and nitrifying bacteria were active in the substrate. Ammonium oxidation rates in column studies ranged from 5 to 10 micrograms N g-1 substrate h-1, and NO2- oxidation rates were 2 to 9.5 micrograms N g-1 substrate h-1. Rates determined from the growth chamber study were approximately 1.2 micrograms N g-1 substrate h-1. Quantities of NH4+ oxidized to NO2- and NO3- in inoculated zeoponic substrate were in excess of plant up-take. Acidification as a result of NH4+ oxidation resulted in a pH decline, and the zeoponic substrate showed limited buffering capacity.
authors.affiliation: Soil and Crop Sciences Department, Texas A&M University, College Station, TX, 77843-2474, USA.
authors.forename: R L
authors.initials: RL
authors.lastname: McGilloway
authors.forename: R W
authors.initials: RW
authors.lastname: Weaver
authors.forename: D W
authors.initials: DW
authors.lastname: Ming
authors.forename: J E
authors.initials: JE
authors.lastname: Gruener
mesh_terms: D001419:Bacteria / Q000378:metabolism; D003470:Culture Media / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007474:Ion Exchange; D009566:Nitrates / Q000032:analysis / Q000378:metabolism / Q000493:pharmacokinetics*; D009573:Nitrites / Q000032:analysis / Q000378:metabolism / Q000493:pharmacokinetics*; D009584:Nitrogen / Q000032:analysis / Q000378:metabolism / Q000493:pharmacokinetics*; D010084:Oxidation-Reduction; D000644:Quaternary Ammonium Compounds / Q000032:analysis / Q000378:metabolism / Q000493:pharmacokinetics*; D031224:Raphanus / Q000254:growth & development / Q000378:metabolism*; D012988:Soil Microbiology; D017641:Zeolites / Q000737:chemistry*
chemical_list: D003470:Culture Media; D009566:Nitrates; D009573:Nitrites; D000644:Quaternary Ammonium Compounds; C083175:clinoptilolite; D017641:Zeolites; D009584:Nitrogen