Phosphorus speciation in the organic layer of two Swedish forest soils 13–24 years after wood ash and nitrogen application

• Changes in P chemistry were determined 13–24 years after wood ash and N application. The speciation forest organic layer was assessed by X-ray micro-spectroscopy. As Ca-bound the dissolved, solubility Al- Fe-bound increased. high of treatment increased uptake trees. fertilization plants decreased easily available P. Application to forests can restore pools phosphorus (P) other nutrients, which are removed following whole tree harvesting. Yet, mechanisms that affect fate ash-P less well known. Previous research into extent application leads soil is contradictory. We combined synchrotron K-edge XANES spectroscopy, µ-XRF microscopy, chemical extractions examine studied horizons two long-term field experiments, Riddarhyttan (central Sweden), had received 3, 6, 9 Mg ha −1 , Rödålund (northern where 3 been applied alone or with every-three since 2003. At latter site, we also aboveground biomass. Overall, between 6 28 kg equivalent 17–39 % initial content ash. Rödålund, there 4.6 (9.5 %) compared 1.6 + < 0.4 control. Riddarhyttan, only highest dose residual (3.8 ). In contrast, Al-bound ( p 0.001) up 15.6 . Moreover, Olsen-P times. There a strong relationship concentrations (R 2 = 0.83, as 0.74, 0.003), suggesting resulted an amount relatively soluble associated hydroxy-Al hydroxy-Fe compounds. Further, 18 increase trees treatment. By repeated fertilization, without ash, reduced Olsen-P. lower extractability concomitant 39 plant treatment, indicates elevated response higher availability. Hence, P, uptake. while increasing uptake, instead did not cause shift speciation.