H.M.Saman K. Herath

Study of the stability of biochar in organic matter-rich soils and its influence on the dynamics of native organic matter
The stability of biochars produced from corn stover (Zea mays L.) at two different temperatures (350 and 550 °C) will be investigated before and after their application to different New Zealand soils, both rich in organic matter but differing in the mechanisms of organic matter stabilization. The research will mainly focus on (i) the determination of the size of the labile and stable fractions of biochar, (ii) the evaluation of whether there is a priming effect of biochars on native organic matter (NOM) decomposition, (iii) the determination of the degree of surface interactions between the biochar particles and soil particles (both organic and inorganic), and (iv) their implications on long-term stability of biochar and NOM in amended soils. A detailed characterisation of the soils will also be carried out giving a special emphasis on the characteristics of the NOM and soil mineralogy. In addition, changes in soil physical properties with the biochars produced at different temperatures will be investigated.
Experiments and analyses will be carried out so that the detailed information on stability of biochars is to be obtained. Biochars will be characterised using different techniques: TGA, BET surface area, FTIR, 13C NMR and XPS spectroscopy. Soil water retention at different matric potential will be also determined. Incubation experiments will be conducted to evaluate the short- and medium-term C stability/mineralization of biochars measuring the δ13C signature in the CO2 evolved. This will be by field experiments, which will be conducted to address and evaluate the above aspects under realistic conditions.
The outcome of this research will be helpful to address some key issues regarding the stability of biochars and that of NOM, as well as on the effects of biochar amendment on soil water retention. It is expected that the findings will also be able to give a feasible method to estimate the intrinsic recalcitrance fraction of biochars. In addition, these findings will provide an insight on, to what extent, the stability of biochar is affected by the interactions with the environment in relation to the intrinsic recalcitrance.

Contact

Email address:Saman.Herath.Mudiyanselage.1@uni.massey.ac.nz

Supervisors

Assoc. Prof. Marta Camps
Prof. Mike Hedley
Dr. Troy Baisden (modelling carbon dynamics)
Dr. Markus Deurer (soil physical properties)

Funding

New Zealand Biochar Research Centre