Abstract

Application of wood ash to forests can restore pools of phosphorus (P) and other nutrients, which are removed following whole tree harvesting. Yet, the mechanisms that affect the fate of ash-P in the organic layer are less well known. Previous research into the extent to which ash application leads to increased P solubility in the soil is contradictory. We combined synchrotron P K-edge XANES spectroscopy, mu-XRF microscopy, and chemical ex-tractions to examine the speciation and solubility of P. We studied organic horizons of two long-term field ex-periments, Riddarhyttan (central Sweden), which had received 3, 6, and 9 Mg ash ha -1, and Ro center dot dalund (northern Sweden), where 3 Mg ash ha- 1 had been applied alone or combined with N every-three years since 2003. At the latter site, we also determined P in aboveground tree biomass. Overall, the ash application increased P in the organic layer by between 6 and 28 kg P ha -1, equivalent to 17-39 % of the initial P content in the applied ash. At Ro center dot dalund, there was 4.6 kg Ca-bound P ha- 1 (9.5 %) in the ash treatment compared to 1.6 kg ha- 1 in the ash + N treatment and < 0.4 kg ha- 1 in the N treatment and the control. At Riddarhyttan, only the treatment with the highest ash dose had residual Ca-bound P (3.8 kg ha -1). In contrast, the ash application increased Al-bound P (p < 0.001) with up to 15.6 kg P ha -1. Moreover, the ash increased Olsen-P by up to two times. There was a strong relationship between the concentrations of Olsen-P and Al-bound P (R2 = 0.83, p < 0.001) as well as Fe-bound P (R2 = 0.74, p = 0.003), suggesting that the ash application resulted in an increased amount of relatively soluble P associated with hydroxy-Al and hydroxy-Fe compounds. Further, there was an 18 % increase in P uptake by trees in the ash treatment. By contrast, repeated N fertilization, with or without ash, reduced Olsen-P. The lower P extractability was concomitant with a 39 % increase in plant P uptake in the N treatment, which indicates elevated P uptake in response to higher N availability. Hence, the application of wood ash increased Al-bound P, easily available P, and P uptake. N fertilization, while also increasing tree P uptake, instead decreased easily available P and did not cause a shift in soil P speciation.

Keywords

P speciation; P solubility; Forest fertilization; P K-edge XANES spectroscopy; ?-XRF imaging microscopy

Published in

Forest Ecology and Management
2022, Volume: 521, article number: 120432
Publisher: ELSEVIER

SLU Authors

• Tuyishime, Marius

  • Department of Soil and Environment, Swedish University of Agricultural Sciences
    

• Adediran, Gbotemi

  • Department of Soil and Environment, Swedish University of Agricultural Sciences
    
  • UK Centre for Ecology and Hydrology (UKCEH)

• Olsson, Bengt

  • Department of Ecology, Swedish University of Agricultural Sciences
    

• Sahlén Zetterberg, Therese

  • Department of Soil and Environment, Swedish University of Agricultural Sciences
    

• Högbom, Lars

  • Department of Forest Ecology and Management, Swedish University of Agricultural Sciences
    
  • Skogforsk

• Spohn, Marie

  • Department of Soil and Environment, Swedish University of Agricultural Sciences
    

• Lim, Hyungwoo

  • Department of Forest Ecology and Management, Swedish University of Agricultural Sciences
    
  • Tartu University Institute of Ecology and Earth Sciences

• Gustafsson, Jon-Petter

  • Department of Soil and Environment, Swedish University of Agricultural Sciences
    

Sustainable Development Goals

Protect, restore and promote sustainable use of terrestrial ecosystems, sustainably manage forests, combat desertification, and halt and reverse land degradation and halt biodiversity loss


UKÄ Subject classification

Forest Science
Soil Science


Publication identifier

DOI: https://doi.org/10.1016/j.foreco.2022.120432

Permanent link to this page (URI)

https://res.slu.se/id/publ/119945