The effect of soil organic matter on long-term availability of phosphorus in soil: evaluation in a biological P mining experiment

A - Papers appearing in refereed journals

Hawkins, J. M. B., Vermeiren, C., Blackwell, M. S. A., Darch, T., Granger, S. J., Dunham, S. J., Hernandez, J. M. B., Smolders, E. and McGrath, S. P. 2022. The effect of soil organic matter on long-term availability of phosphorus in soil: evaluation in a biological P mining experiment. Geoderma. 423, p. 115965. https://doi.org/10.1016/j.geoderma.2022.115965

AuthorsHawkins, J. M. B., Vermeiren, C., Blackwell, M. S. A., Darch, T., Granger, S. J., Dunham, S. J., Hernandez, J. M. B., Smolders, E. and McGrath, S. P.
Abstract

The plant uptake of legacy phosphorus (P) from over-fertilised agricultural soils could offer a solution to decrease dependency on finite mineral P resources. This study evaluated the long-term availability of legacy P in soils with an accelerated biological mining assay, thereby testing to what extent this availability is affected by soil organic carbon (SOC). A 15-months long pot trial was set-up, in which 25 soils with 1.2-24% SOC were mined for P by continuous cropping and harvesting of ryegrass (Lolium Perenne) in a plant growth cabinet. The cumulative uptake of P was, on average, 19% of the P associated with poorly crystalline iron (Fe) and aluminium (Al) (oxy)hydroxides (oxalate-extractable P; Pox), and half of this uptake occurred fast enough to maintain crop production at an adequate level of > 90% of its potential. This P available for adequate uptake (PUA) strikingly matched with the isotopically exchangeable P or “E value” of a soil (median PUA/E24h = 0.81), whereas it was markedly underestimated by Olsen P (median PUA/POlsen = 1.51). The fractions of plant-available Pox increased at increasing ratios of P and SOC to Feox and Alox, showing that enhanced SOC contents reduce ageing of P by preventing its diffusion into micropores. That effect of SOC on P availability was more pronounced in soils with a low initial P saturation status. The comparison of the results from biological mining with available soil P pools determined in a (sterile) P desorption experiment could not confirm a significant contribution of organic P to plant P supply. Our findings suggest that legacy P in well-fertilised agricultural soils could act as a sufficient P source for plants for 12-175 years, and that this long-term availability is positively affected by SOC as long as the soil is not too highly saturated with P.

KeywordsAccelerated biological mining; Ageing; Availability; Long-term; Phosphorus; Soil organic carbon
Year of Publication2022
JournalGeoderma
Journal citation423, p. 115965
Digital Object Identifier (DOI)https://doi.org/10.1016/j.geoderma.2022.115965
Open accessPublished as non-open access
FunderBiotechnology and Biological Sciences Research Council
Funder project or codeS2N - Soil to Nutrition - Work package 1 (WP1) - Optimising nutrient flows and pools in the soil-plant-biota system
BBS/EC/00005197
The Rothamsted Long Term Experiments [2017-2022]
Output statusPublished
Publication dates
Online03 Jun 2022
Publication process dates
Accepted26 May 2022
ISSN0016-7061
PublisherElsevier Science Bv

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