Agronomic values of greenwaste biochar as a soil amendment

Tom Miles

Agronomic values of greenwaste biochar as a soil amendment
K. Y. Chan, L. Van Zwieten, I. Meszaros, A. Downie,and S. Joseph
Australian Journal of Soil Research 45(8) 629

Article > Contents Vol 45(8)

Agronomic values of greenwaste biochar as a soil amendment

K. Y. Chan A E, L. Van Zwieten B, I. Meszaros A, A. Downie C D, S. Joseph D

A NSW Department of Primary Industries, Locked Bag 4, Richmond, NSW 2753, Australia.
B NSW Department of Primary Industries, Wollongbar, NSW 2477, Australia.
C Best Energies P/L, Somersby, NSW 2250, Australia.
D University of New South Wales, School of Materials Science and Engineering, Sydney, NSW 2052, Australia.
E Corresponding author. Email:

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Soil Research 45(8) 629–634
Submitted: 27 July 2007 Accepted: 2 November 2007 Published online: 7 December 2007


A pot trial was carried out to investigate the effect of biochar produced from greenwaste by pyrolysis on the yield of radish (Raphanus sativus var. Long Scarlet) and the soil quality of an Alfisol. Three rates of biochar (10, 50 and 100 t/ha) with and without additional nitrogen application (100 kg N/ha) were investigated. The soil used in the pot trial was a hardsetting Alfisol (Chromosol) (0–0.1 m) with a long history of cropping. In the absence of N fertiliser, application of biochar to the soil did not increase radish yield even at the highest rate of 100 t/ha. However, a significant biochar × nitrogen fertiliser interaction was observed, in that higher yield increases were observed with increasing rates of biochar application in the presence of N fertiliser, highlighting the role of biochar in improving N fertiliser use efficiency of the plant. For example, additional increase in DM of radish in the presence of N fertiliser varied from 95% in the nil biochar control to 266% in the 100 t/ha biochar-amended soils. A slight but significant reduction in dry matter production of radish was observed when biochar was applied at 10 t/ha but the cause is unclear and requires further investigation.

Significant changes in soil quality including increases in pH, organic carbon, and exchangeable cations as well as reduction in tensile strength were observed at higher rates of biochar application (>50 t/ha). Particularly interesting are the improvements in soil physical properties of this hardsetting soil in terms of reduction in tensile strength and increases in field capacity.
Keywords: charcoal, char, agrichar, soil strength, soil carbon sequestration, hardsetting soil, slow pyrolysis.