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

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)

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

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

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 = 12.5739, df = 11, p-value = 7.186e-08 Significant lower labile P concentrations than total P concentrations

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 15.2294 0.0045 ** Tree species 0.6219 0.4530 Soil horizon x tree species 0.5464 0.4808 Residuals --- Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1 Significant effect of soil horizon on the concentrations of labile P

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 0.1724 0.688 Tree species 1.0042 0.345 Soil horizon : tree species 3.5156 0.097 . Residuals --- Signif. codes: 0 '***' 0.001 '**' 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

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 30.3805 0.00056 *** Tree species 2.4252 0.15801 Soil horizon : tree species 0.0132 0.91123 Residuals --- Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1 Significant effect of soil horizon on the ratio of labile P/total P

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)

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

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