NITROGEN TRANSFORMATIONS DURING ANAEROBICALLY STORED N-15-LABELED PIGSLURRY

Different forms of nitrogen: dissolved inorganic-N (or total ammonium- N), suspended organic-N and dissolved organic-N were followed during a naerobic storage of N-15 labelled pig slurry The kinetics of nitrogen transformations were recorded at 0, 1, 3, 7, 14, 28, 63 and 84 days du ring a laboratory incubation. At day 0, N-15 enriched urea (150 mgN/kg of slurry with a isotopic excess of 50%) was added to the slurry Afte r a rapid total hydrolysis of the urea (within 1 day), a continuous de cay of the suspended organic-N fraction was observed concurrently with the increase in the total ammonium-N pool. This mineralization reache d 19% of the initial total organic-N fraction, resulting in an increas e of the fetal ammoniacal nitrogen content from 2410 to 2780 mgN-NH4+/ kg of slurry Labelling techniques allowed measurement of a simultaneou s slight immobilization (into the suspended organic-N fraction) of 4.6 % of the initial ammoniacal-N. (C) 1998 Elsevier Science Ltd. All righ ts reserved.