Transformations of mineral nitrogen applied to peat soil during sequential oxic/anoxic cycling

Levin Pal (Author), Blaž Stres (Author), Tjaša Danevčič (Author), Simona Leskovec (Author), Ines Mandić-Mulec (Author)

Abstract

Shifts in oxic and anoxic conditions in soil are most frequently caused by water table fluctuations, heavy rain, snowmelt or flooding, with potentially significant impacts on microbial processes and the ability of soils to convert mineral nitrogen gases efficiently. The impact of oxic/anoxic cycles on nitrogen transformation rates was therefore explored in the upper layer (0-30 cm) of partially degraded peat soil. We hypothesized that high denitrification potential would be conserved due to the high organic matter content of this soil. Mineral nitrogen was applied to approximately 1-cm deep layers of homogenized soil in microcosms, with no external source of readily degradable carbon. Microcosms were subjected to three cycles, each consisting of an oxic phase of 8-11 days and an anoxic phase of 21-28 days. Approximately 2% of the ammonium load was lost through ammonia volatilization during oxic phases and the remainder was nitrified. The accumulated nitrate decreased soil ph from 8.0 to 6.8 before its transformation through denitrification. Nitrification and denitrification rates during the three oxic/anoxic cycles (approximately three months) were.29-3.2 kg N ha [up]-1 and 1.0-2.3 kg N ha[up]-1, respectively. Extrapolation of these values to 30-cm deep soil layers gave rates that were sufficient for complete transformation of at least 1700 kg N ha [up]-1 of ammonium to nitrogen gases, which is ten-fold greater than the annual nitrogen application of 170 kg N ha[up]-1 permitted by the European directive. Denitrification rates decreased linearly during the three cycles (from 36+-2 to 16+-ug N g [up-1] d [up]-1 drysoil projecting cessation of denitrification activity and Co2 production during the fifth cycle. Storage of peat at 4oC most probably allowed slow degradation of organic matter that was completely oxidized to Co2 after the soil was exposed to higher temeprature (28oC). Storage of soil for one year did not affect nitrification rate, but reduced denitrifation rate, unless soilwas amended with a readily degradable carbon source. The data suggest thatthe high carbon content of this soil, it cannot sustain transformations ofhigh N loads to nitrogen gases for prolonged periods without amendment with readily available carbon.

Keywords

varstvo okolja;tla;šota;dušik;kroženje dušika;nitrifikacija;dentrifikacija;

Data

Language:	English
Year of publishing:	2010
Typology:	1.01 - Original Scientific Article
Organization:	UL BF - Biotechnical Faculty
UDC:	502
COBISS:	2619272
ISSN:	0038-0717
Views:	1928
Downloads:	287
Average score:	0 (0 votes)
Metadata:

Other data

Secondary language:	Slovenian
Secondary keywords:	varstvo okolja;tla;šota;dušik;kroženje dušika;nitrifikacija;dentrifikacija;
Type (COBISS):	Not categorized
Pages:	str. 1338-1346
Volume:	ǂIssue ǂ8
Issue:	ǂVol. ǂ42
Chronology:	2010
DOI:	10.1016/j.soilbio.2010.03.013
ID:	21484