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Long-term phosphorus supply in agricultural soils : size and dynamics of fast- and slow-desorbing phosphorus pools

Braun, Sabina (2020). Long-term phosphorus supply in agricultural soils : size and dynamics of fast- and slow-desorbing phosphorus pools. Diss. (sammanfattning/summary) Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae, 1652-6880
ISBN 978-91-7760-632-1
eISBN 978-91-7760-633-8
[Doctoral thesis]

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Abstract

To improve phosphorus (P) fertiliser management, a better understanding of inorganic P exchange between the soil solution and solid phase is needed. This thesis examined the dynamics of this exchange, distinguishing between pools of P that are fast- and slowdesorbing, and compared methods for quantification of these pools. This was done using soil and data from six locations in the Swedish long-term soil fertility trials. Treatments with four levels of P addition, from zero P to replacement + 30 kg P ha−1 , were sampled. Isotopic exchange kinetics (IEK) were used to study the dynamics and size of the isotopically exchangeable P pools. The size of the isotopically exchangeable pool at t=1 min (E1 min) was affected by exchangeable Ca2+, while that of the E1 day − E1 min and E3 months − E1 day pools was affected by soil pH and Al-ox + Fe-ox. The change in P-Olsen and P-ox over time was also related to exchangeable Ca2+. Phosphorus desorption kinetics were tested with iron(hydr)oxide-coated papers as an ‘unlimited’ sink. The P desorption values were fitted to the Lookman two-compartment model, giving information about the size and desorption rate of the fast- and slow-desorbing P pools (Q1 and Q2). The desorption experiments was shown to deliver similar information as the IEK, even if they assess different mechanisms.

Two extraction methods (AL and Olsen) were tested for their ability to quantify the fast-desorbing P pool, by incubation of soil with radioactive 33P before extraction. This revealed that AL extraction dissolves more stable P forms, which was further proved by the relationship between P-AL and Q1 (r2 =0.63) being weaker than for P-Olsen and Q1 (r2 =0.96).

A positive P balance increased the amount of ‘P bound to Al and Fe’, and/or CaP, (according to P K-edge XANES), the desorption rate from the slow-desorbing P pool and the fraction of total P present in the fast-desorbing pool. It did not increase wheat, barley, or oat grain yield. With no P fertiliser, the extractable and exchangeable P pools decreased, but about half locations had significantly lower grain yield. This shows that the P contribution from the slow-desorbing P pool is important for plant P uptake, and that this pool can supply P for a long period. When replacement P was added, yields was not affected but P-AL and P-Olsen decreased, making ‘P in balance’ a possibly useful strategy to lower soil P levels without grain yield loss.

Authors/Creators:Braun, Sabina
Title:Long-term phosphorus supply in agricultural soils : size and dynamics of fast- and slow-desorbing phosphorus pools
Year of publishing :2020
Number:2020:57
Number of Pages:75
Publisher:Department of Soil and Environment, Swedish University of Agricultural Sciences
ISBN for printed version:978-91-7760-632-1
ISBN for electronic version:978-91-7760-633-8
ISSN:1652-6880
Language:English
Publication Type:Doctoral thesis
Article category:Other scientific
Version:Published version
Full Text Status:Public
Subjects:(A) Swedish standard research categories 2011 > 4 Agricultural Sciences > 401 Agricultural, Forestry and Fisheries > Agricultural Science
Keywords:phosphorus desorption, isotopic exchange kinetics, 33P, long-term field experiments, P K-edge XANES, phosphorus balance, grain production
URN:NBN:urn:nbn:se:slu:epsilon-p-108625
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-p-108625
ID Code:18682
Faculty:NJ - Fakulteten för naturresurser och jordbruksvetenskap
Department:(NL, NJ) > Dept. of Soil and Environment
(S) > Dept. of Soil and Environment
Deposited By: SLUpub Connector
Deposited On:17 Nov 2020 12:37
Metadata Last Modified:17 Nov 2020 13:54

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