Table 3.
Concentrations of P and cations in each extract for each soil
| Extractant | AR-control | AR-N | AR-PL | AR-PL-alum | SK | PEI | Till Ref | ||
|---|---|---|---|---|---|---|---|---|---|
| TP | Mehlich III | Soil | 64 (13) | 84 (16) | 382 (32) | 675 (55) | 99 (18) | 244 (22) | 30 (3) |
| NaOH-EDTA | Residue | 255 (53) | 306 (58) | 601 (50) | 1101 (90) | 204 (36) | 396 (36) | 328 (35) | |
| NaOH-EDTA | Soil | 282 (59) | 327 (62) | 753 (63) | 1178 (97) | 340 (60) | 759 (69) | 360 (39) | |
| NaOH-EDTA | Difference | 27 (6) | 21 (4) | 152 (13) | 77 (7) | 136 (24) | 363 (33) | 32 (4) | |
| MUP | Mehlich III | Soil | 33 (53) | 25 (33) | 4 (< 1) | 306 (41) | 33 (39) | 33 (14) | 1 (3) |
| Al | Mehlich III | Soil | 421 | 695 | 506 | 1205 | 671 | 1256 | 1683 |
| Fe | Mehlich III | Soil | 106 | 220 | 160 | 161 | 146 | 216 | 335 |
| Mn | Mehlich III | Soil | 112 | 54 | 113 | 32 | 174 | 29 | 179 |
| Ca | Mehlich III | Soil | 1152 | 376 | 1547 | 853 | 1548 | 441 | 972 |
| Mg | Mehlich III | Soil | 148 | 49 | 266 | 112 | 347 | 53 | 161 |
Concentrations are given in mg kg−1 soil. MUP, concentration of molybdate-unreactive P, determined as the difference in P measured by ICP and colorimetrically (percent of total soil P recovered in M3 extract). All other concentrations determined by ICP-OES. Residue, residual soil after Mehlich III extraction; TP, total P in each extract (percent of total soil P recovered in each extract). Difference is the difference in between the NaOH-EDTA extracts of whole soils and the NaOH-EDTA extracts of the residue after Mehlich III extraction