Table 1.
Properties of the bulk soil and rhizosphere samples from soybean cultivated at the flowering–podding stage and maturity stage under different fertilization levels.
| Treatments | CK | PK | PK + N | PK + R | |
|---|---|---|---|---|---|
| Flowering-podding stage | |||||
| pH | Bulk soil | 5.96 ± 0.02a | 5.47 ± 0.01d | 5.66 ± 0.01c | 5.75 ± 0.01b |
| Rhizosphere | 6.16 ± 0.02a* | 5.61 ± 0.03d* | 5.85 ± 0.01c* | 5.99 ± 0.01b* | |
| OM (g kg−1) | Bulk soil | 28.92 ± 0.67a | 29.68 ± 1.31a | 30.85 ± 1.35a | 30.50 ± 1.51a |
| Rhizosphere | 28.55 ± 1.74a | 28.38 ± 0.29a | 30.81 ± 1.45a | 29.89 ± 0.82a | |
| TN (g kg−1) | Bulk soil | 1.71 ± 0.04ab | 1.66 ± 0.03b | 1.75 ± 0.04a | 1.67 ± 0.06ab |
| Rhizosphere | 2.03 ± 0.08a | 1.76 ± 0.13b | 1.91 ± 0.12ab | 1.88 ± 0.09ab* | |
| AN (mg kg−1) | Bulk soil | 122.10 ± 4.70ab | 118.48 ± 3.30b | 125.14 ± 1.08a | 116.30 ± 3.03b |
| Rhizosphere | 125.37 ± 2.67a | 120.84 ± 2.94a | 127.90 ± 5.66a | 124.99 ± 5.13a | |
| AP (mg kg−1) | Bulk soil | 21.43 ± 0.60c | 78.27 ± 1.11a* | 63.93 ± 1.59b* | 64.60 ± 0.69b |
| Rhizosphere | 20.80 ± 1.47d | 67.70 ± 0.70a | 48.97 ± 0.60c | 63.57 ± 1.55b | |
| AK (mg kg−1) | Bulk soil | 126.15 ± 1.32c | 182.73 ± 4.06b | 199.58 ± 6.50a | 204.97 ± 3.75a |
| Rhizosphere | 132.59 ± 2.70c* | 238.94 ± 7.65a* | 197.34 ± 2.60b | 242.18 ± 3.38a* | |
| Nodule dry weight (g) | 1.48 ± 0.06ab | 1.98 ± 0.34a | 1.17 ± 0.44b | 1.57 ± 0.06ab | |
| Maturity stage | |||||
| pH | Bulk soil | 6.24 ± 0.03a* | 6.02 ± 0.01b* | 5.85 ± 0.01c | 6.02 ± 0.00b |
| Rhizosphere | 5.93 ± 0.02b | 5.95 ± 0.01ab | 5.87 ± 0.02c | 5.98 ± 0.03a | |
| OM (g kg−1) | Bulk soil | 30.09 ± 0.75ab | 29.06 ± 0.17c | 30.76 ± 0.08a | 29.86 ± 0.46bc |
| Rhizosphere | 31.48 ± 0.59ab | 30.78 ± 0.74b* | 32.10 ± 0.44a* | 32.49 ± 0.63a* | |
| TN (g kg−1) | Bulk soil | 1.56 ± 0.03a | 1.49 ± 0.02a | 1.45 ± 0.28a | 1.56 ± 0.03a |
| Rhizosphere | 1.68 ± 0.01a* | 1.72 ± 0.06a* | 1.71 ± 0.04a | 1.70 ± 0.03a* | |
| AN (mg kg−1) | Bulk soil | 138.35 ± 3.49a | 140.31 ± 3.31a | 140.68 ± 5.70a | 144.34 ± 4.81a |
| Rhizosphere | 142.72 ± 2.62a | 150.38 ± 3.60a* | 143.08 ± 3.96a | 142.41 ± 5.59a | |
| AP (mg kg−1) | Bulk soil | 17.40 ± 1.66d | 49.13 ± 1.37c | 57.77 ± 1.20b* | 68.40 ± 1.44a* |
| Rhizosphere | 19.27 ± 1.50d | 54.90 ± 0.78b* | 50.37 ± 0.71c | 58.33 ± 1.23a | |
| AK (mg kg−1) | Bulk soil | 146.47 ± 1.05b | 143.73 ± 2.96b | 168.65 ± 1.69a | 163.00 ± 5.96a |
| Rhizosphere | 218.40 ± 46.05ab | 191.44 ± 1.55b* | 246.39 ± 8.77a* | 251.03 ± 7.14a* | |
| Soybean yield (kg ha−1) | 2287.60 ± 119.86b | 2856.67 ± 160.32a | 2881.33 ± 173.27a | 3025.33 ± 131.37a | |
Soil properties were calculated for each replicate of fertilizer treatment and bulk soil/rhizosphere samples (n = 3). Data are the means ± standard deviation. CK: non-inoculated control in soil; PK, superphosphorus and potassium chloride; PK + N, PK chemical fertilizers plus urea; PK + R, PK chemical fertilizers plus Bradyrhizobium japonicum 5821. Different letters in each column of same fertilization treatment indicate significant difference among treatments in different stage (p < 0.05). The asterisks indicate the significance of the difference between the indexes of bulk and rhizosphere soil under the same treatment during the same growth stage (p < 0.05).