The significance of stable P forms in soil · In the end: A model to more accurately predict the...
Transcript of The significance of stable P forms in soil · In the end: A model to more accurately predict the...
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The significance of stable P forms in soilSabina BraunSLU
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Photo: Jenny Svennås-Gillner, SLU
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Soil P test(P-AL)
Which crop?
Expected yield?
Fertilizer recommendation
ßIs this the best test?
What about P availability?
For all soils?
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Solution P Labile P Stable P
SOIL P TEST TARGET TODAY
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So what are we doing?
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Long-term fertility experiments
Photo: Magnus Simonsson och Gunnar Börjesson.
P-balancesChanges in P pools
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Sink methods
Iron oxide coated filter papersPhoto: Sabina Braun
Dialysis membrane tube filled with ferrihydratePhoto: Sabina Braun
P desorption rates
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Isotopic exchange kinetics31P
31P
31P31P
31P
31P 31P
31P
31P
33P
31P
31P
31P
31P
33P33P
33P
31P
33P31P
31P
31P
31P
31P
31P
P exchange ratesAmount of exchangeable P
Sorbed soil P
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Summary• P balances over 50 yrs
• Changes in P pools
• Desorbable P
• Exchangable P
• Soil properties
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In the end: A model to more accurately predict the plant-available P pool, considering both:
– The size of the labile and stable P pool
How should it be measured?
and
– The transfer of P between labile and stable pools
What soil properties control this transfer?
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Transfer between
pools
Size oflabile pool
Which crop?
Expected yield?
Fertilizerrecommendation
ß Estimated by relevant soil properties
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