Nitrification-denitrification dynamics and community structure of ammonia oxidizing bacteria in a high yield irrigated Philippine rice field.
Nitrogen is the single most limiting factor for rice production. Detailed knowledge on nitrogen dynamics in rice fields is therefore of major importance for developing sustainable rice production. A combination of state-of-the-art microsensor, stable isotope tracer, and molecular techniques was used to evaluate coupled nitrification-denitrification potentials and community structure of ammonia-oxidizing bacteria in a high yield irrigated rice cropping system in the Philippines, without the use of microcosm incubations. The multiple approaches showed a high degree of concordance among methods and thereby clarified the investigated processes. Numbers and potential activity of ammonia-oxidizing bacteria in the system reflected the availability of substrate in three defined soil factions with a ranking of: surface soil > rhizosphere > bulk soil. No nitrification activity was measured between spit applications of N fertilizer. However, nitrification was induced upon nitrogen amendment in intact soil cores. Despite induction by nitrogen amendment, the loss of nitrogen through coupled nitrification-denitrification was less than 10% of the plant nitrogen uptake. Denaturant gradient gel electrophoresis of amoA fragments revealed no differences in diversity profiles between the soil fractions, and phylogenetic analysis, based on amoA genes retrieved from the rice paddy soil, identified a set of mutually very similar sequences related to Nitrosomonas nitrosa.
Nicolaisen
Mette Haubjerg
MH
Department of Microbial Ecology, Institute of Biological Sciences, University of Aarhus, DK-8000 Aarhus C, Denmark. meni@kvl.dk
Risgaard-Petersen
Nils
N
Revsbech
Niels Peter
NP
Reichardt
Wolfgang
W
Ramsing
Niels Birger
NB
D000383:Agriculture; D000641:Ammonia / Q000378:metabolism*; D017753:Ecosystem; D004591:Electrophoresis, Polyacrylamide Gel; D008969:Molecular Sequence Data; D009566:Nitrates / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism; D009606:Nitrosomonas / Q000145:classification / Q000201:enzymology / Q000254:growth & development* / Q000378:metabolism; D012275:Oryza / Q000254:growth & development*; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism; D010679:Philippines; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D012988:Soil Microbiology
D009566:Nitrates; D000641:Ammonia; D010088:Oxidoreductases; C045582:ammonia monooxygenase; D009584:Nitrogen