Combining field incubation with nitrogen-15 labelling to examine nitrogen transformations in low to high intensity grassland management systems

Hatch, D. J.; Jarvis, S. C.; Parkinson, Robert; Lovell, R. D.

doi:10.1007/s003740050028

Cited by 51 publications

(56 citation statements)

References 22 publications

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“…Surprisingly, our analysis of the group of studies with a fertilization treatment showed no effect of fertilization on any variable, although individual studies did detect significant increases in mineralization, nitrification, or both with fertilization (Hungate et al 1997b, Ledgard et al 1998, Hall and Matson 1999, Zaman et al 1999, Bradley et al 2000a, Hatch et al 2000a, Fisk and Fahey 2001, Nishio et al 2001, Stockdale et al 2002. There is evidence to suggest that the nature of the amendment makes a difference.…”

Section: Fertilization Effects On Gross Ratesmentioning

confidence: 82%

Controls on Nitrogen Cycling in Terrestrial Ecosystems: A Synthetic Analysis of Literature Data

Booth

Stark

Rastetter

2005

Ecological Monographs

899

105

729

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Abstract. Isotope pool dilution studies are increasingly reported in the soils and ecology literature as a means of measuring gross rates of nitrogen (N) mineralization, nitrification, and inorganic N assimilation in soils. We assembled data on soil characteristics and gross rates from 100 studies conducted in forest, shrubland, grassland, and agricultural systems to answer the following questions: What factors appear to be the major drivers for production and consumption of inorganic N as measured by isotope dilution studies? Do rates or the relationships between drivers and rates differ among ecosystem types? Across a wide range of ecosystems, gross N mineralization is positively correlated with microbial biomass and soil C and N concentrations, while soil C:N ratio exerts a negative effect on N mineralization only after adjusting for differences in soil C. Nitrification is a log-linear function of N mineralization, increasing rapidly at low mineralization rates but changing only slightly at high mineralization rates. In contrast, NH 4 ϩ assimilation by soil microbes increases nearly linearly over the full range of mineralization rates. As a result, nitrification is proportionately more important as a fate for NH 4 ϩ at low mineralization rates than at high mineralization rates. Gross nitrification rates show no relationship to soil pH, with some of the fastest nitrification rates occurring below pH 5 in soils with high N mineralization rates. Differences in soil organic matter (SOM) composition and concentration among ecosystem types influence the production and fate of mineralized N. Soil organic matter from grasslands appears to be inherently more productive of ammonium than SOM from wooded sites, and SOM from deciduous forests is more so than SOM in coniferous forests, but differences appear to result primarily from differing C:N ratios of organic matter. Because of the central importance of SOM characteristics and concentrations in regulating rates, soil organic matter depletion in agricultural systems appears to be an important determinant of gross process rates and the proportion of NH 4 ϩ that is nitrified. Addition of 15 N appears to stimulate NH 4 ϩ consumption more than NO 3 Ϫ consumption processes; however, the magnitude of the stimulation may provide useful information regarding the factors limiting microbial N transformations.

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Section: Fertilization Effects On Gross Ratesmentioning

confidence: 82%

Controls on Nitrogen Cycling in Terrestrial Ecosystems: A Synthetic Analysis of Literature Data

Booth

Stark

Rastetter

2005

Ecological Monographs

899

105

729

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“…Long-term-unfertilized plots were dominated by Holcus lanatus, Lolium perenne, Agrostis stolonifera, and Phleum pratense, whereas those soils under long-term inorganic N fertilizer management (200 kg N ha Ϫ1 year Ϫ1 ) were dominated by Holcus lanatus. The N dynamics of the fertilized and unfertilized plots have been studied in detail previously (28) and demonstrated NH 4 ϩ concentrations of 5.9 and 3.7 mg of N · kg of dry soil Ϫ1 and significantly different (P ϭ 0.09) nitrification rates of 1.6 and 1.0 g of N g Ϫ1 day Ϫ1 for the long-term-fertilized and unfertilized plots, respectively. For this study, 10 2-m-by-3-m subplots were constructed separately within a long-term-fertilized plot and an unfertilized plot.…”

Section: Methodsmentioning

confidence: 96%

Influence of Inorganic Nitrogen Management Regime on the Diversity of Nitrite-Oxidizing Bacteria in Agricultural Grassland Soils

Freitag

Chang

Clegg³

et al. 2005

Appl Environ Microbiol

133

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To assess links between the diversity of nitrite-oxidizing bacteria (NOB) in agricultural grassland soils and inorganic N fertilizer management, NOB communities in fertilized and unfertilized soils were characterized by analysis of clone libraries and denaturing gradient gel electrophoresis (DGGE) of 16S rRNA gene fragments. Previously uncharacterized Nitrospira-like sequences were isolated from both long-term-fertilized and unfertilized soils, but DGGE migration patterns indicated the presence of additional sequence types in the fertilized soils. Detailed phylogenetic analysis of Nitrospira-like sequences suggests the existence of one newly described evolutionary group and of subclusters within previously described sublineages, potentially representing different ecotypes; the new group may represent a lineage of noncharacterized Nitrospira species. Clone libraries of Nitrobacter-like sequences generated from soils under different long-term N management regimes were dominated by sequences with high similarity to the rhizoplane isolate Nitrobacter sp. strain PJN1. However, the diversity of Nitrobacter communities did not differ significantly between the two soil types. This is the first cultivation-independent study of nitrite-oxidizing bacteria in soil demonstrating that nitrogen management practices influence the diversity of this bacterial functional group.Nitrogen fertilization is the most important management strategy for the improvement of agricultural crops. However, up to 60% of N fertilizer applied can be lost through leaching of mobile N compounds (NO 3 Ϫ ) and transformation into N 2 O and N 2 (53), leading to water pollution and contributing to global warming. The key process during natural N cycling is microbial chemolithoautotrophic nitrification, the conversion of NH 4 ϩ to NO 3 Ϫ via NO 2 Ϫ . Autotrophic nitrification is carried out by two distinct groups, ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB), and it is generally assumed that the first step is rate-limiting (50). This assumption is based mainly on observations that NO 2 Ϫ concentrations are low or negligible in most natural systems. Consequently, with the exception of high-N-load sewage-processing systems, where nitrite concentrations are high (NO 2 Ϫ -N up to 70 mg liter Ϫ1 ) (17, 22) and nitrite washout is of concern (41, 63), research into community composition, activity, and environmental responses of nitrifying bacteria has focused on AOB (37). These studies have demonstrated the influence of land use management regimes on the diversity and activity of AOB, as well as links to changes in ammonia oxidation rates (4, 9, 11, 49, 70), but a comprehensive understanding of soil nitrification also requires characterization of NOB.Analysis of NOB in natural environments has been limited by reliance on traditional, cultivation-based methods. In contrast to AOB, for which most 16S rRNA gene sequences of cultured organisms and related environmental clones fall within a monophyletic group (51, 66), NOB are classified into...

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“…For the mean pool dilution technique it is necessary to add enough 15 N to be able to measure the decrease in enrichment caused by dilution of the added 15 …”

Section: Methodsmentioning

confidence: 99%

High rates of nitrogen cycling in volcanic soils from Chilean grasslands

Dixon

Cardenas

Alfaro³

et al. 2011

Rapid Comm Mass Spectrometry

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There are over one million hectares of pasture in Chile, and 80% and 50% of the country's milk and meat comes from 72% of this area, situated in the lake region of southern Chile. The soils are volcanic and a major characteristic is that they have very high organic matter (OM) contents with the potential to support plant growth with only moderate levels of added nitrogen (N). To understand better the potential fertility of these soils in order to maximise production and minimise losses of N, we undertook studies using the stable isotope of N ((15)N) to resolve the rates of the main internal N cycling processes in three soils representing the two main volcanic soil types: Osorno and Chiloé (Andisol) and Cudico (Ultisol). We also assessed the longer-term potential of these soils to sustain N release using anaerobic incubation. Gross rates (µg N g(-1) day(-1)) of mineralisation were 27.9, 27.1 and 15.5 and rates of immobilisation were 5.9, 12.0 and 6.3 for Osorno, Chiloé and Cudico, respectively, implying high rates of net mineralisation in these soils. This was confirmed by anaerobic incubation which gave potential seasonal net mineralisation indices of 1225, 1059 and 450 kg N ha(-1) in the top 10 cm soil layers of the three soils. However, plant production may still benefit from added N, as the release of N from organic sources may not be closely synchronised with crop demand. The low rates of nitrification that we found with these acidic soils suggest that the more mobile N (viz. nitrate-N) would be in limited supply and plants would have to compete for the less mobile ammonium-N with the soil microbial biomass. Nitrogen was mineralised in appreciable amounts even down to 60 cm depth, so that leaching could become significant, particularly if the soils were limed, which could enhance nitrification and N mobility through the soil profile.

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Combining field incubation with nitrogen-15 labelling to examine nitrogen transformations in low to high intensity grassland management systems

Cited by 51 publications

References 22 publications

Controls on Nitrogen Cycling in Terrestrial Ecosystems: A Synthetic Analysis of Literature Data

Controls on Nitrogen Cycling in Terrestrial Ecosystems: A Synthetic Analysis of Literature Data

Influence of Inorganic Nitrogen Management Regime on the Diversity of Nitrite-Oxidizing Bacteria in Agricultural Grassland Soils

High rates of nitrogen cycling in volcanic soils from Chilean grasslands

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