Evaluation of phosphorus in thermally converted sewage sludge: P pools and availability to wheat
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(Accepted version)
Date
2017
Authors
Mackay, J.
Cavagnaro, T.
Jakobsen, I.
Macdonald, L.
Grønlund, M.
Thomsen, T.
Müller-Stöver, D.
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Plant and Soil: international journal on plant-soil relationships, 2017; 418(1-2):307-317
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Jessica E. Mackay, Timothy R. Cavagnaro, Iver Jakobsen, Lynne M. Macdonald, Mette Grønlund, Tobias P. Thomsen, Dorette S. Müller-Stöver
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Abstract
Aims: Dried sewage sludge (SS) and the by-products of four SS thermal conversion processes (pyrolysis, incineration and two types of gasification) were investigated for phosphorus (P) availability. Methods: A sequential extraction was used to determine the distribution of P among different P pools. After mixing materials with soil, availability of the P was determined with soil P extractions and in a growth experiment with wheat. Results: Thermally converted SS contained a greater proportion of P within recalcitrant pools than dried SS. Despite having very different P pool distributions, the incinerated and dried SS provided similar amounts of P to plants. Plant P supply from dried and incinerated SS was lower than the comparable soluble P treatment (50 mg P kg⁻¹), but higher than a soluble treatment at a lower rate (20 mg P kg⁻¹). Plant P uptake in gasified and pyrolysed treatments was only marginally greater than uptake in a control (no P) treatment. Plant P uptake correlated most closely with diffusive gradients in thin films (DGT) P analysis of soil-material mixes. Phosphorus availability in the dried and incinerated SS treatments increased over time. Conclusions: We propose that the dried and incinerated SS have potential as slow release P fertilisers in low pH soils.
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© Springer International Publishing Switzerland 2017