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Type: Theses
Title: The influence of temperature on emissions of nitrous oxide and dinitrogen from soils
Author: Lai, Thang Viet
Issue Date: 2016
School/Discipline: School of Agriculture, Food and Wine
Abstract: Nitrification and denitrification are two major soil biological processes that release nitrous oxide (N₂O) from soils. N₂O production and reduction have been well-documented at temperatures below 35ºC, but are poorly understood at higher temperatures. N₂O production from nitrification was compared at a range of temperatures (10ºC to 45ºC) to mimic the typical temperatures encountered in soils from dairy pasture systems in Australia. Temperature was more important than soil type in controlling N₂O from nitrification, which was slow at 10 – 25ºC and peaked at 35 – 40ºC, suggesting a higher optimum temperature for N₂O production from nitrification than previous studies reported. Autotrophic nitrification produced N₂O predominantly below 35ºC, while heterotrophic nitrification, which used NH₄⁺ for nitrifying, released N₂O principally between 35ºC and 40ºC. Total N₂O emissions measured at different temperatures were influenced by the climatic region from which the soils were sourced. The magnitudes of N₂O emissions in the tropical soil exceeded those in the temperate soil under experimental conditions, although N₂O/NO₃⁻ from nitrification at different temperatures was independent of the climatic region from which soils were sourced. The N₂O/NO₃⁻ ratio was positively correlated with increased temperature and was above 1.0% at 35ºC, regardless of climate. Temperature interacted with soil moisture and NO₃⁻ availability to regulate N₂O from denitrification, while the conversion of N₂O to N₂ was affected principally by temperature. The highest denitrification (N₂O + N₂) was found at 35ºC in the soils treated at 75% FC and N contents between 100 – 150 kg N ha⁻¹. Low N₂O/N₂ ratios at 40 – 45ºC was due to the enhancement of N₂ production at these temperatures, suggesting greater soil NO₃⁻ loss as N₂ during summer, particularly in soils that are wet at that time. Interestingly, high NH₄⁺ availability was observed at 45ºC, which was hypothesised to relate to low nitrification rate and high rates of N mineralisation or dissimilatory nitrate reduction to ammonium at this temperature. This work has improved the knowledge of N cycling processes at high temperatures. Soil moisture or NO₃⁻ content alone are poor predictors of N₂O and N₂ production, since these elements interacted with temperature to control denitrification. High soil NH₄⁺ availability at 45ºC is a particularly interesting finding with potential to contribute to N losses. The findings confirm that management of soil moisture and NO₃⁻ availability, and a consideration of crop N demand are likely to reduce N losses as N₂O and N₂.
Advisor: Denton, Matthew
Farquharson, Ryan
Bolan, Nanthi
Dissertation Note: Thesis (Ph.D.) (Research by Publication) -- University of Adelaide, School of Agriculture, Food and Wine, 2016.
Keywords: temperature
nitrous oxide
Provenance: This electronic version is made publicly available by the University of Adelaide in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. This thesis may incorporate third party material which has been used by the author pursuant to Fair Dealing exceptions. If you are the owner of any included third party copyright material you wish to be removed from this electronic version, please complete the take down form located at:
DOI: 10.4225/55/58ad182189332
Appears in Collections:Research Theses

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