Table 2. The concentration and proportion of P fractions in soil profiles under three irrigation patterns.
| Soil | Methods | Soil P forms (mg/kg) | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Depth (cm) | H2O-Pi | H2O-Po | NaHCO3-Pi | NaHCO3-Po | NaOH-Pi | NaOH-Po | HCl-P | Residual-P | |
| 0–10 | FIA | 56.2a (1.77) | 47.1a (1.48) | 468.2a (14.72) | 184.3a (5.79) | 792.6a (24.92) | 277.1a (8.71) | 972.3a (30.57) | 382.4a (12.03) |
| SURB | 51.4a (2.09) | 38.3b (1.56) | 374.5b (15.25) | 151.6b (6.17) | 642.0b (26.14) | 213.2b (8.68) | 710.3b (28.92) | 275.1b (11.2) | |
| SDIC | 42.0b (1.79) | 27.3c (1.16) | 335.6c (14.29) | 148.7b (6.33) | 574.9c (24.48) | 203.0b (8.64) | 789.0c (33.59) | 228.2c (9.72) | |
| 10–20 | FI | 48.1a (1.67) | 35.9a (1.25) | 416.1a (14.46) | 167.1a (5.81) | 721.5a (25.06) | 236.4a (8.21) | 921.4a (32.01) | 331.9a (11.53) |
| SUR | 49.9a (2.08) | 31.6a (1.32) | 361.6b (15.07) | 142.8b (5.95) | 633.8b (26.41) | 208.2b (8.68) | 708.0b (29.5) | 264.1b (11) | |
| SDI | 40.5b (2.03) | 23.0b (1.15) | 290.2c (14.55) | 137.1b (6.83) | 470.3c (23.59) | 166.7c (8.36) | 703.0b (35.26) | 164.1c (8.23) | |
| 20–30 | FI | 34.9a (1.63) | 24.0ab (1.17) | 416.1a (12.81) | 128.0a (5.99) | 509.2a (23.85) | 181.6a (8.51) | 726.2a (34.01) | 256.9a (12.03) |
| SUR | 37.0a (1.76) | 25.4a (1.21) | 361.6b (15.44) | 105.2b (5.02) | 545.3b (26.02) | 180.7a (8.62) | 645.5b (30.8) | 233.2b (11.13) | |
| SDI | 35.7a (2.33) | 18.9b (1.15) | 290.2c (13.03) | 71.5c (4.34) | 401.9c (24.39) | 128.8b (7.81) | 638.2b (38.72) | 135.7c (8.23) | |
| 30–40 | FI | 29.5a (1.95) | 20.0a (1.32) | 248.4a (16.45) | 94.6a (6.26) | 296.4a (19.69) | 138.3a (9.16) | 505.4a (33.46) | 176.8a (11.71) |
| SUR | 25.1a (1.55) | 17.2ab (1.07) | 277.3a (17.18) | 85.4a (5.29) | 359.1b (22.25) | 126.5a (7.84) | 542.6b (33.62) | 180.5a (11.19) | |
| SDI | 28.8a (2.56) | 14.6b (1.29) | 109.1b (9.67) | 38.2b (3.39) | 219.2c (19.43) | 95.3b (8.45) | 428.2c (37.95) | 194.8a (17.27) | |
| 40–60 | FI | 14.5b (1.67) | 11.1a (1.27) | 102.7a (b (11.79) | 60.7a (6.97) | 114.5a (13.13) | 70.5a (8.09) | 361.3a (41.45) | 136.2a (15.63) |
| SUR | 12.3b (1.16) | 8.1a (0.76) | 133.6a (12.58) | 69.5a (6.54) | 150.7b (14.18) | 92.5b (8.71) | 454.0b (42.74) | 140.5a (13.32) | |
| SDI | 24.2a (2.92) | 10.5a (1.27) | 69.3b (8.11) | 20.7b (2.5) | 174.5c (21.02) | 54.0a (6.51) | 352.8a (42.5) | 126.0a (15.18) | |
Different lowercase letters indicate a significant difference at P <0.05 between treatments in each soil horizon.
Values in parenthesis represent proportion (%) of TP in soil.
A furrow irrigation.
B surface drip irrigation.
C subsurface drip irrigation.