University of Wollongong Research Online Faculty of Science, Medicine & Health - Honours Theses University of Wollongong Thesis Collections 2012 Forms of C, N and P accumulation under different pasture soil carbon sequestration scenarios Richard Lawless University of Wollongong Follow this and additional works at: https://ro.uow.edu.au/thsci University of Wollongong Copyright Warning You may print or download ONE copy of this document for the purpose of your own research or study. The University does not authorise you to copy, communicate or otherwise make available electronically to any other person any copyright material contained on this site. You are reminded of the following: This work is copyright. Apart from any use permitted under the Copyright Act 1968, no part of this work may be reproduced by any process, nor may any other exclusive right be exercised, without the permission of the author. 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Recommended Citation Lawless, Richard, Forms of C, N and P accumulation under different pasture soil carbon sequestration scenarios, Bachelor of Environmental Science (Honours), School of Earth & Environmental Science, University of Wollongong, 2012. https://ro.uow.edu.au/thsci/46 Research Online is the open access institutional repository for the University of Wollongong. For further information contact the UOW Library: [email protected] Forms of C, N and P accumulation under different pasture soil carbon sequestration scenarios Abstract Sequestering carbon and managing nutrients in soils are key issues in global agriculture. Understanding the quantities involved and the major processes of change are vital for improved utility of soils. Fertilised pasture soils potentially contain large pools of carbon, nitrogen and phosphorus. A knowledge of the amount and distribution of nutrients stored in such soils can have positive implications for sequestering carbon in order to mitigate anthropogenic climate change, reducing nutrient runoff and improving soil fertility. In this study, the soil carbon, nitrogen and phosphorus contents were determined for six fields of varying fertility, across two dairy farms in the Camden region of NSW. Three profiles were examined to 100 cm depth, to investigate the distribution and nutrient forms in the different soil layers. Profiles were described and sampled, and samples were analysed for total carbon, total nitrogen, organic and inorganic phosphorus. Ancillary data such as particle size distribution and bulk densities were also measured. Total quantities of C, N and P and nutrient ratios were calculated for each of the fields. Results showed large amounts of nutrients were contained in the topsoils, and also in the deeper 30-70 cm profile layers that are not commonly analysed. Total carbon contents ranged between 170,184 - 292,278 kg/ha, total nitrogen from 11,562 - 21,780 kg/ha and total phosphorus from 1,586 - 4,035 kg/ha. Large variations were found between the different fertility fields, particularly in the inorganic phosphorus content where some soils contained a possible P surplus. An average C:N:P ratio of 192:12:1 was calculated across all soils sampled. This is similar to values found elsewhere for pasture soils. Well managed pasture soils were shown to have potential to sequester large additional amounts of carbon. It is recommend that fertiliser application rates be based on regular soil testing, and appropriate management strategies be developed to effectively manage nutrient accumulation and distribution. Degree Type Thesis Degree Name Bachelor of Environmental Science (Honours) Department School of Earth & Environmental Science Advisor(s) John Morrison Keywords Soil, carbon, nitrogen, phosphorus, sequestration, dairy pasture This thesis is available at Research Online: https://ro.uow.edu.au/thsci/46 Forms of C, N and P accumulation under different pasture soil carbon sequestration scenarios Richard Lawless A research report submitted in partial fulfilment of the requirements for the award of the degree of HONOURS BACHELOR OF ENVIRONMENTAL SCIENCE ENVIRONMENTAL SCIENCE PROGRAM FACULTY OF SCIENCE THE UNIVERSITY OF WOLLONGONG OCTOBER 2012 ii Abstract Sequestering carbon and managing nutrients in soils are key issues in global agriculture. Understanding the quantities involved and the major processes of change are vital for improved utility of soils. Fertilised pasture soils potentially contain large pools of carbon, nitrogen and phosphorus. A knowledge of the amount and distribution of nutrients stored in such soils can have positive implications for sequestering carbon in order to mitigate anthropogenic climate change, reducing nutrient runoff and improving soil fertility. In this study, the soil carbon, nitrogen and phosphorus contents were determined for six fields of varying fertility, across two dairy farms in the Camden region of NSW. Three profiles were examined to 100 cm depth, to investigate the distribution and nutrient forms in the different soil layers. Profiles were described and sampled, and samples were analysed for total carbon, total nitrogen, organic and inorganic phosphorus. Ancillary data such as particle size distribution and bulk densities were also measured. Total quantities of C, N and P and nutrient ratios were calculated for each of the fields. Results showed large amounts of nutrients were contained in the topsoils, and also in the deeper 30-70 cm profile layers that are not commonly analysed. Total carbon contents ranged between 170,184 - 292,278 kg/ha, total nitrogen from 11,562 - 21,780 kg/ha and total phosphorus from 1,586 - 4,035 kg/ha. Large variations were found between the different fertility fields, particularly in the inorganic phosphorus content where some soils contained a possible P surplus. An average C:N:P ratio of 192:12:1 was calculated across all soils sampled. This is similar to values found elsewhere for pasture soils. Well managed pasture soils were shown to have potential to sequester large additional amounts of carbon. It is recommended that fertiliser application rates be based on regular soil testing, and appropriate management strategies be developed to effectively manage nutrient accumulation and distribution. iii Acknowledgements This thesis would not have been possible without the generous support from a number of people. First and foremost I would like to thank Professor John Morrison from the School of Earth and Environmental sciences at the University of Wollongong. His continual guidance and encouragement ensured the project stayed on track and maintained my motivation, while his prompt feedback and depth of knowledge never failed to amaze me. I am very grateful to have had John as my supervisor. Secondly I would like to thank Warwick Dougherty from the NSW Department of Primary Industries. Warwick’s support, effort and knowledge in both the field and lab aspects of the project were deeply appreciated. Without his hard work and guidance the sampling and analysis would have been far more difficult. I would also like to thank the staff at the NSW DPI Richmond laboratory for their help with the sample analyses. I would also like to thank my family back home in Victoria for their continual encouragement throughout both this honours thesis and my entire undergraduate degree. They have always been there for me and supported me in all my decisions. I would like to thank Marina McGlinn for helping to organise the project, and for her understanding and flexibility in organising the initial project meetings when I was becalmed offshore on my slow return to Australia. Finally I would like to thank all my friends and housemates for their support and encouragement throughout the year, for helping me work through the project, and giving me something to look forward to outside of university. iv Table of Contents Abstract ................................................................................................................................................... ii Acknowledgements ................................................................................................................................ iii List of figures .......................................................................................................................................... vi List of Tables ......................................................................................................................................... vii 1. Introduction .................................................................................................................................... 1 1.1. The global carbon cycle ........................................................................................................... 1 1.2. Carbon and nutrient sequestration in soils............................................................................. 2 1.3. The Australian situation .........................................................................................................