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Table 1 Depth resolved phosphorus (P) stocks and the composition of NaOH–EDTA extractable soil P, as assessed by the liquid 31P-NMR spectroscopy of homogenized composite samples (n = 3) of three long-term experimental sites

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

Management Depth P recovery Phosphonate Orthophophate Monoesters Diesters Pyrophosphate Extractable Po Extractable Pt
> 20 ppm 6.7 to 6.0 ppm 6.9 to 6.7, 6.0 to 3.5 ppm 2 to − 2 ppm − 4.3 ppm
cm % kg ha−1 (%)
Dahlem
 Control 0–30 30 0.0 (0) 627 (80) 144 (18) 4.5 (0.6) 6.2 (0.8) 148 (19) 781
30–50 19 0.0 (0) 191 (96) 8 (4) 0.0 (0) 0.0 (0) 8 (4) 199
70–90 10 0.0 (0) 172 (100) 0.0 (0) 0.0 (0) 0.0 (0) 0 172
 Mineral + organic P 0–30 45 0.0 (0) 989 (85) 162 (14) 3.3 (0.3) 6.8 (0.6) 166 (14) 1162
30–50 51 0.0 (0) 410 (98) 10 (2) 0.0 (0) 0.0 (0) 10 (2) 420
70–90 15 0.0 (0) 186 (100) 0.0 (0) 0.0 (0) 0.0 (0) 0 186
Freising Dürnast
 Control 0–30 57 0.0 (0) 825 (67) 392 (32) 6.8 (0.6) 9.2 (0.7) 398 (32) 1233
30–60 40 3.5 (0.4) 477 (50) 461 (49) 1.9 (0.2) 6.2 (0.7) 466 (49) 949
60–90 47 0.0 (0) 557 (62) 339 (38) 0.0 (0) 4.9 (0.5) 339 (38) 901
 Mineral + organic P 0–30 64 3.1 (0.2) 1187 (72) 442 (27) 5.8 (0.3) 10.2 (0.6) 451 (27) 1648
30–60 37 2.2 (0.2) 514 (52) 454 (46) 3.7 (0.4) 5.3 (0.5) 460 (47) 979
60–90 48 0.0 (0) 787 (68) 358 (31) 0.0 (0) 4.9 (0.4) 358 (31) 1150
Bad Lauchstädt
 Control 0–30 39 0.0 (0) 336 (46) 386 (53) 2.7 (0.4) 8.4 (1.1) 388 (53) 733
30–60 28 0.0 (0) 117 (39) 177 (59) 3.4 (1.1) 1.0 (0.3) 180 (60) 299
60–90 11 0.0 (0) 54 (52) 50 (48) 0.0 (0) 0.0 (0) 50 (48) 103
 Mineral + organic P 0–30 56 0.0 (0) 1554 (82) 328 (17) 9.4 (0.5) 9.0 (0.5) 338 (18) 1901
30–60 39 0.0 (0) 750 (71) 299 (28) 5.7 (0.5) 4.0 (0.4) 305 (29) 1059
60–90 35 0.0 (0) 384 (67) 187 (33) 1.3 (0.2) 0.0 (0) 189 (33) 572
  1. The values in parentheses (%) represent the individual P forms as a proportion of total NaOH–EDTA extractable soil P. The content of diesters and monoesters were corrected by considering P hydrolysis during extraction