Kirsten Ball

Candidature

PhD Candidate

Thesis title

Microbially mediated soil carbon sequestration in agroecosystems

Research Project

Land conversion for cropping alters soil carbon (C) accumulation in multiple ways: 1) tilling, which directly reduces the protection of stable soil aggregates; 2) vegetation removal, which directly reduces organic matter accumulation; and 3) fertilisation which alters both the amount and quality of organic matter deposition, as well as its microbially-mediated decomposition. Appropriate management of agricultural systems has the potential to increase storage of organic carbon and improve nutrient cycling, benefiting both producers and the planet by reducing the costs associated with inputs and improving soil functional health. My PhD thesis is a cotutelle arrangement with the University of Aberdeen to examine how differential agricultural management affects nutrient cycling and soil carbon storage. Combining field experiments at established Australian pasture and vineyard field sites with a greenhouse experiment at the Australian Plant Phenomics facility I will examine plant and microbial interactions driving carbon storage and nutrient cycling. At the University of Aberdeen, I will explore the future implications of agricultural manipulations on carbon storage using soil carbon modelling.

I aim to understand how soil carbon accumulation is affected over a fertiliser induced stoichiometric gradient in grass and legume mixtures compared with monocultures, as well as to quantify the role of microbial carbon use efficiency in mediating soil C accumulation under these different scenarios. To integrate my data from the field and laboratory experiments into soil carbon models I will combine soil fractionation and nuclear magnetic resonance imagery to derive measured carbon fractions that can be directly related to conceptual pools in the RothC model with the ultimate aim to optimise agricultural management towards increasing soil carbon sequestration.

Supervisors

Professor Elise Pendall, Professor Sally Power, Dr Sarah Woodin (University of Aberdeen), and Professor Pete Smith (University of Aberdeen).