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Table 2 Depth resolved phosphorus (P) speciation (% proportion of total P) of three long-term P fertilization sites (P-fertilized and non-P-fertilized (control), as obtained by linear combination fitting (LCF) on averaged P K-edge XANES spectra

From: Subsoils—a sink for excess fertilizer P but a minor contribution to P plant nutrition: evidence from long-term fertilization trials

Site Treatment Depth (cm) Ca-associated P Al-associated P Fe-associated P Organic-associated P R-factor
ACP Hydroxyapatite CaHPO4 × 2H2O AlPO4 P sorbed on gibbsite P sorbed on goethite Phytic acid
Dahlem Control 0–30 19 ± 1     4 ± 4 68 ± 2 7 ± 1 0.003103
30–50 2 ± 2     36 ± 0 58 ± 1 4 ± 2 0.010016
70–90   40    23 36   0.006228
Mineral + organic P 0–30 11 ± 9 7 ± 10   24 ± 6 26 ± 10 25 ± 19 8 ± 6 0.003642
30–50 6 ± 6 5 ± 5   27 ± 1   52 ± 1 10 ± 0 0.003893
70–90 34 ± 3   4 ± 6   13 ± 1 44 ± 0 3 ± 4 0.003781
Freising Dürnast Control 0–30 20    15   44 21 0.002441
30–60 7    0 12 57 24 0.004938
60–90 11    21   49 19 0.003804
Mineral + organic P 0–30 21    9   52 19 0.002279
30–60   8   15   55 27 0.003750
60–90     11   73 15 0.003848
Bad Lauchstädt Control 0–30 27      47 26 0.003704
30–60 52     21   27 0.004682
60–90 56     27   17 0.005963
Mineral + organic P 0–30 49     31   19 0.002447
30–60 43     13 20 25 0.003174
60–90 47     26   27 0.005464
  1. ACP amorphous calcium phosphate