Abstract

Efficient phosphorus (P) fertilization strategies are essential for intensive crop production with minimal negative environmental impacts. A key factor in sustainable P use is assessment of the plant available soil P pool using soil P tests. This study determined isotopically exchangeable P after six days of reaction with (PO4)-P-33 (P-E (6 d)) to determine how accurately two commonly used P tests, Olsen and AL (acid ammonium acetate lactate) can quantify the amount of labile P. Soil samples were taken from both highly P-amended and unamended plots at six sites within the Swedish long-term soil fertility experiments. According to P K-edge XANES spectroscopy, the P speciation was dominated by Al-bound P and organic P, with additional contributions from Fe-bound P and Ca phosphates in most soils. The results showed that the AL test overestimated P-E (6 d) by a factor of 1.70 on average. In contrast, the Olsen test underestimated P-E (6 d), with the mean ratios of P-Olsen to P-E (6 d) being 0.52 for high-P and 0.19 for low-P soils. The P-33/P-31 ratio in the Olsen extract of a (PO4)-P-33 spiked soil was closer to that of a 0.005 mol L-1 CaCl2 soil extract than the corresponding ratio in the AL extract, suggesting that AL extraction solubilized more non-labile P. In conclusion, the AL and Olsen methods are not suitable for direct quantification of the isotopically exchangeable soil P pool after 6 days of equilibration. However, based on the results, Olsen may be superior to AL for classification of soil P status, due to its even performance for calcareous and non-calcareous soils and lower extraction of non-labile P.

Keywords

Soils; Phosphorus; Chemical analysis; Isotopes P-33; Soil P test; Isotopic exchange kinetic technique

Published in

Geoderma
2019, Volume: 337, pages: 350-358
Publisher: ELSEVIER SCIENCE BV

SLU Authors

• Braun, Sabina

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

• Börjesson, Gunnar

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

• Ulen, Barbro

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

• Gustafsson, Jon-Petter

  • Department of Soil and Environment, Swedish University of Agricultural Sciences
    
  • Royal Institute of Technology (KTH)

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
End hunger, achieve food security and improved nutrition and promote sustainable agriculture
Ensure sustainable consumption and production patterns


UKÄ Subject classification

Soil Science


Publication identifier

DOI: https://doi.org/10.1016/j.geoderma.2018.09.048

Permanent link to this page (URI)

https://res.slu.se/id/publ/98332