Isotopically enriched ammonium shows high nitrogen transformation in the pile top zone of dairy manure compost

摘要

Nitrogen isotope ratios (iδ/isup15/supN) of NHsub4/subsup+/sup in dairy manure compost piles with and without bulking agent (10?%?iw/i∕iw/i) were compared to understand the effects of the use of bulking agent on nitrogen conversion during manure composting. The iδ/isup15/supN–NHsub4/subsup+/sup values in each of three pile zones (top, side and core) were also compared. At the end of the process, piles with bulking agent showed significantly higher iδ/isup15/supN values (17.7?±?1.3?‰) than piles without bulking agent (11.8?±?0.9?‰), reflecting the significantly higher nitrogen conversion and NHsub3/sub loss in the former. The samples from the top zone, especially in the piles with bulking agent, showed very high NHsub4/subsup+/sup concentrations with significantly high sup15/supN (iδ/isup15/supN: 12.7–29.8?‰) values, indicating that extremely high nitrogen conversion, nitrification–denitrification activity of the microbes and NHsub3/sub volatilization occurred in this zone.