The role of organic nitrogen in the nutrition of Eucalyptus
Access status:
Open Access
Type
ThesisThesis type
Doctor of PhilosophyAuthor/s
Simpson, JacquelynAbstract
Nitrogen availability commonly limits plant growth. Addition of N fertiliser alleviates N limitation and increases productivity but can have significant environmental and economic costs, providing incentives to optimise fertiliser application with accurate predictive tests to ...
See moreNitrogen availability commonly limits plant growth. Addition of N fertiliser alleviates N limitation and increases productivity but can have significant environmental and economic costs, providing incentives to optimise fertiliser application with accurate predictive tests to diagnose N limitation. Traditionally N limitation has been ascertained under the premise that plants are only capable of taking up inorganic nitrogen. We now suspect that organic nitrogen could also play a role in plant nutrition, but additional research is required before organic N can be used as the basis for diagnostic tests of N limitation. The aim of this thesis is to increase our understanding of the role of organic N in nutrition of two plantation tree species, Eucalyptus nitens and Eucalyptus globulus, to determine a simple and robust method of indicating nitrogen limitation. Protease activity and total exchangeable amino acid concentration are strongly correlated with N-limitation in E. nitens forestry plantation soils. Although there is minimal seasonal variation in protease activity, we measured significant seasonal variation in the absolute and relative abundance of small (<250 Da) dissolved organic and extracted inorganic and organic nitrogen compounds of E. nitens plantations. Strong correlation between nitrogen limitation and the abundance of ammonium, nitrate and amino acids in soil extracts are consistent with a growing body of literature arguing plants can take up organic nitrogen compounds. Our results indicate depolymerisation (protease activity) is the rate limiting step of N availability. Organic nitrogen is abundant in soil, taken up by plants and strongly related to N-limitation. Protease activity is a strong indicator of N-limitation with great potential as a reliable and ubiquitous indicator of N-limitation in soils
See less
See moreNitrogen availability commonly limits plant growth. Addition of N fertiliser alleviates N limitation and increases productivity but can have significant environmental and economic costs, providing incentives to optimise fertiliser application with accurate predictive tests to diagnose N limitation. Traditionally N limitation has been ascertained under the premise that plants are only capable of taking up inorganic nitrogen. We now suspect that organic nitrogen could also play a role in plant nutrition, but additional research is required before organic N can be used as the basis for diagnostic tests of N limitation. The aim of this thesis is to increase our understanding of the role of organic N in nutrition of two plantation tree species, Eucalyptus nitens and Eucalyptus globulus, to determine a simple and robust method of indicating nitrogen limitation. Protease activity and total exchangeable amino acid concentration are strongly correlated with N-limitation in E. nitens forestry plantation soils. Although there is minimal seasonal variation in protease activity, we measured significant seasonal variation in the absolute and relative abundance of small (<250 Da) dissolved organic and extracted inorganic and organic nitrogen compounds of E. nitens plantations. Strong correlation between nitrogen limitation and the abundance of ammonium, nitrate and amino acids in soil extracts are consistent with a growing body of literature arguing plants can take up organic nitrogen compounds. Our results indicate depolymerisation (protease activity) is the rate limiting step of N availability. Organic nitrogen is abundant in soil, taken up by plants and strongly related to N-limitation. Protease activity is a strong indicator of N-limitation with great potential as a reliable and ubiquitous indicator of N-limitation in soils
See less
Date
2015-06-25Faculty/School
Faculty of Science, School of Biological SciencesAwarding institution
The University of SydneyShare