Good day,

We took samples of willows ‘Bjørn’ (Svalöf-Weibull (SW) 910006, S. schwerinii E. Wolf × S. viminalis) harvested in a constructed wetland treating household wastewater.

By doing Hedley P sequential extraction in triplicates, we observed that the HCL-P is relatively high compared with the H2O-P, NaHCO3-P, and NaOH-P.

From the inorganic P, the HCL-P account, on average, 61% with SD of 10.5%.

H2O-P (28%), NaHCO3-P (3%), NaOH-P (7%)

The HCL-P might mean the insoluble fraction, usually related to apatite minerals and calcium phosphates, when the extraction is used for soil samples.

I would appreciate it if you could give me some ideas of what could be the reason for those results.

Recently calcium phosphate has been found in trichomes of several plant families, including Brassicaceae (Maximilian Weigend et al 2017) .

But I do not see a reason for such a difference in our experiments.

Thank you.