Table 2.
Soil pH, acid phosphatase activity, and citrate and malate concentration in the rhizosphere of wheat grown with different P supplies. Each value is the mean (±SE) of five replicates. Different letters in a given column denote significant differences between P rates (P ≤ 0.05).
| P rate (mg P per kg soil) | Rhizosphere soil pH | Bulk soil pH | Rhizosphere soil pH change | Acid phosphatase activity (μg PNP per h per g soil) | Citrate (nmol per g soil) | Malate (nmol per g soil) |
|---|---|---|---|---|---|---|
| 0 | 8.00 ± 0.05a | 8.19 ± 0.01ab | 0.18 ± 0.05d | 117 ± 3cd | 237 ± 29bcd | 0 ± 0d |
| 2.5 | 8.02 ± 0.02a | 8.20 ± 0.00a | 0.18 ± 0.02d | 162 ± 18bc | 244 ± 15abc | 0 ± 0d |
| 5 | 7.97 ± 0..05a | 8.19 ± 0.01ab | 0.22 ± 0.05d | 203 ± 31ab | 260 ± 34ab | 44 ± 44d |
| 10 | 7.91 ± 0.04a | 8.22 ± 0.01a | 0.31 ± 0.05d | 175 ± 18abc | 295 ± 29a | 31 ± 31d |
| 25 | 7.62 ± 0.05b | 8.20 ± 0.01a | 0.59 ± 0.06c | 234 ± 31a | 194 ± 16cde | 143 ± 43c |
| 50 | 7.56 ± 0.04b | 8.19 ± 0.01ab | 0.63 ± 0.04c | 190 ± 51ab | 195 ± 22cde | 185 ± 16bc |
| 75 | 7.42 ± 0.04c | 8.22 ± 0.01a | 0.80 ± 0.05b | 92 ± 6d | 167 ± 16ef | 192 ± 19bc |
| 150 | 7.36 ± 0.03cd | 8.20 ± 0.00a | 0.84 ± 0.03ab | 122 ± 16cd | 168 ± 25def | 259 ± 40ab |
| 300 | 7.33 ± 0.06cd | 8.15 ± 0.02b | 0.82 ± 0.06ab | 153 ± 13bcd | 138 ± 17ef | 214 ± 23bc |
| 600 | 7.27 ± 0.05d | 8.21 ± 0.04a | 0.95 ± 0.06a | 146 ± 16bcd | 121 ± 15f | 261 ± 39ab |
| 1200 | 7.28 ± 0.03d | 7.91 ± 0.04c | 0.63 ± 0.02c | 166 ± 15abc | 107 ± 16f | 313 ± 28a |