Nutrient changes in potting mix and Eucalyptus nitens leaf tissue under macadamia biochar amendments

A. Wrobel-Tobiszewska*, M. Boersma, J. Sargison, P. Adams, B. Singh, Stewart Franks, C. J. Birch, D. C. Close

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

21 Citations (Scopus)


The effect of macadamia nut shell biochar on nitrogen, potassium, phosphorus, magnesium, calcium and sodium concentrations in potting mix used to grow Eucalyptus nitens seedlings was investigated in a glasshouse experiment. The treatments combined two fertiliser rates (50 and 100% rate of the commercial mix commonly used in forestry nurseries) with eight biochar rates (0, 2, 5, 10, 20, 50, 80 and 100 t ha−1) arranged in a randomised complete block with three replicates of four sample plants. Nutrients were quantified in the potting mix and seedling leaves at four destructive harvests 135, 177, 219 and 269 days after planting. Biochar significantly increased nitrate-N, Colwell P, Colwell K and exchangeable Na and reduced ammonium-N, Mg and Ca concentrations in the potting mix. Seedling leaf concentrations of P, K and Na were increased by biochar application, while N remained dependent on fertiliser rate only. Mg and Ca leaf concentrations decreased in response to increasing biochar rates. Elevated nitrate-N and decreased ammonium-N concentrations suggest that biochar might have increased nitrification in the potting mix. We presumed that biochar mediated processes that reduced uptake of P and K when high doses of biochar were combined with full fertilisation. Changes in potting mix K, Na, Mg and Ca were consistent with selective adsorption of ions to biochar surfaces.

Original languageEnglish
Pages (from-to)383-393
Number of pages11
JournalJournal of Forestry Research
Issue number2
Early online date12 Jun 2017
Publication statusPublished - Mar 2018


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