Biochar and the soil nitrogen cycle: unravelling the interactions

Daniel Dempster

Research output: ThesisDoctoral Thesis

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Abstract

[Truncated abstract] Methods of sequestering carbon (C) are being investigated to mitigate the current trend of increasing atmospheric carbon dioxide concentration. Furthermore, since the onset of intensive farming practices soil organic matter (SOM) content has declined in many soil types throughout the world. The application of pyrolysed organic matter, or biochar, to soil can maintain higher soil C. The application of biochar to soil has also been shown to potentially improve soil fertility and enhance yields of crops such as maize, wheat and peanuts. However, biochar amendment changes many soil properties but the mechanism by which biochar alters soil processes and plant growth is not always clear. This thesis focuses primarily on those changes that are directly linked to the soil nitrogen (N) cycle. Biochar has been reported to have a large nutrient and water retention capacity; which may cause decreases in N leaching with its application to soil. Biochar can contain labile C and is also highly porous, potentially providing a substrate for microbial utilisation and a habitat for microbial colonisation. Biochar addition to soil can increase microbial abundance and activity. Previous research has hypothesised that this may be responsible for enhanced N mineralisation rates that contribute to the demonstrated improvements of N fertiliser use efficiency (up to 90%) in glasshouse-based agronomic research. The sandy soils that are widespread throughout the broadacre agricultural region of Western Australia (WA) naturally have low water (2-10% v/v) and nutrient retention capacities and low SOM content. Thus the sandy soils of WA are an environment in which biochar amendment is likely to influence soil N cycling. This provided the premise for the investigation into how biochar interacts with the soil N cycle (mineralisation, nitrification, immobilisation, N sorption, leaching, and plant N uptake) in coarse-textured soils of Western Australian broadacre agriculture...
Original languageEnglish
QualificationDoctor of Philosophy
Publication statusUnpublished - 2013

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