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Evaluation of phosphorus in thermally converted sewage sludge: P pools and availability to wheat

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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.

OriginalsprogEngelsk
TidsskriftPlant and Soil
Vol/bind418
Udgave nummer1-2
Sider (fra-til)307-317
Antal sider11
ISSN0032-079X
DOI
StatusUdgivet - 2017

ID: 193502915