1. Phosphatfractions in litter/soil
Introduction
Methods
Extraction method by Hedley
Measuring method
Results and discussion
Chemische Methoden WS09/10
Ralph Steingruber
Johannes Kobler

2. Introduction Major P originates from primary minerals -> Apatit
Negligible P through air
P in soil solution is very low
HPO42- / H2PO4- for uptake
“Young“ soils have more P than „old“ ones
often a limiting factor for plant growth
-> Mykorrhiza and MO in Rhizophere are important for P uptake
-> Organic layer is important and rapid cycling pool
-> cycling time depend from many factors (pH, MO, fungi, weathering status/age)

3. Method Hedley fractionation: Sequencial extraction plant available
Labile P
Hedley fractionation:
Sequencial extraction
Often used method
Best approach to separate labile and stable P
Stable P

4. Method Photometric mesuring with Molybden blue Soil / litter Phospho-
molybdate blue
882 nm
Bicarbonate
Plant available P
HNO3 + HClO4
„acid digestion“ -> total P
Extraction/Digestion
Measuring
Calculation
Calculations

5. Results and discussion
Labile vs. total P
(mg P kg-1 d.w.) 
Mean SD
Bicarbonat-
extraction
10,1
5,4
Acid-digestion
420,5
113,9
Paired t-test
t = , df = 11, p-value = 7.186e-08
Significant lower labile P concentrations
than total P concentrations

6. Results and discussion
Labile P
(mg P kg-1 d.w.)  
Mean SD
Oak - Organic layer
12,6
6,7
Oak - Mineral soil
6,0
1,1
Beech - Organic layer
15,8
0,9
Beech - Mineral soil
6,1
2,4
F value Pr(>F)
Soil horizon **
Tree species
Soil horizon x tree species
Residuals
---
Signif. codes: 0 '***' '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
Significant effect of soil horizon
on the concentrations of labile P

7. Results and discussion
Total P
  (mg P kg-1 d.w.)
Mean SD
Oak - Organic layer
381,0
125,5
Oak - Mineral soil
521,2
135,2
Beech - Organic layer
434,5
70,3
Beech - Mineral soil
345,1
77,3
F value Pr(>F)
Soil horizon
Tree species
Soil horizon : tree species
Residuals
---
Signif. codes: 0 '***' '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
Remarkable:
Oak Organic layer < Oak Mineral soil
No significant effect of soil horizon, tree species
and interaction term on the concentrations of total P

8. Results and discussion
Labile P/total P (%)
(mg P kg-1 d.w.)  
Mean SD
Oak - Organic layer
3,2
0,7
Oak - Mineral soil
1,2
0,4
Beech - Organic layer
3,7
Beech - Mineral soil
1,8
0,6
F value Pr(>F)
Soil horizon ***
Tree species
Soil horizon : tree species
Residuals
---
Signif. codes: 0 '***' '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
Significant effect of soil horizon
on the ratio of labile P/total P

10. Discussion
P concentrations in forest floor > P concentrations in mineral soil
due to the input via litter fall
Soils without carbonate in Austria: Forest floor: 836 mg kg-1
Mineral soil: 396 mg kg-1
Content of organically bound P increases with C concentration within same soil type
P forms strong innerspheric compounds
Properties for P sorption:
pH, Fe-and Al-oxides, clay minerals, calcite, P already sorbed in soil
P sorption increases in acid (sorption to Fe and Al-oxides)
and alkaline soils (formation of hardly soluble Ca-phosphates)

12. Mean SD Oak 9,3 5,6 Beech 10,9 5,5 Mean SD Oak 451,1 139,7 Beech 389,8
Mean SD
Oak
9,3
5,6
Beech
10,9
5,5
Mean SD
Oak
451,1
139,7
Beech
389,8
82,2
Mean SD
Organic layer
14,2
4,6
Mineral soil
6,1
1,6
Mean SD
Organic layer
407,8
95,6
Mineral soil
433,2
137,9
Mean SD
Organic layer
3,4
0,7
Minerla soil
1,5
0,6
Mean SD
Oak
2,2
1,2
Beech
2,7

13. Chemically and physically organic P
Introduction
Functional concept P fractions
Inorganic
Organic
Stabile
Labile
Labile
Stabile
Primary
minerals
Solution
P in Plants, MOs
Chemically and physically organic P
Secondary
minerals
Labile P
Labile P
Many different forms of P in soil / litter
cycling time depend from many factors (pH, MO, fungi, weathering status/age)
P turnover and Concentration mostly in upper soil