TABLE 1.
Effects of Nitrogen levels on the nodulation characteristics of different soybean cultivars.
| Sample code | Treatment | Nodule no. (plant–1) | Nodule mass (g plant–1) | Ethylene (μmol/plant/h) | Available nitrogen (mg/Kg) | Chlorophyll content (SPAD) | Height (cm) | Dry weight of upground (g/Plant) | Dry weight of root (g/Plant) | |
| Cultivar | N-supp. mg/kg | |||||||||
| H-N0 | Heihe 38 | 0 | 129.67 ± 27.43a | 6.50 ± 1.01b | 92.37 ± 23.42a | 53.02 ± 2.22a | 18.81 ± 2.38cd | 27.82 ± 2.87bc | 9.24 ± 1.18ab | 5.13 ± 0.70abc |
| H-N1 | 50 | 255.33 ± 21.55a | 6.93 ± 0.76b | 125.59 ± 24.34a | 56.49 ± 2.03abc | 16.67 ± 0.84bc | 34.42 ± 4.64d | 12.25 ± 3.84b | 5.91 ± 1.15c | |
| H-N2 | 100 | 207.00 ± 14.18a | 4.03 ± 0.61a | 131.13 ± 32.81ab | 62.57 ± 3.32d | 21.38 ± 2.76de | 30.17 ± 4.40cd | 14.67 ± 3.68b | 6.42 ± 0.78c | |
| H-N3 | 150 | 123.67 ± 46.48a | 3.00 ± 0.90a | 75.53 ± 44.37a | 70.52 ± 2.49e | 22.51 ± 5.16de | 31.18 ± 5.54cd | 12.29 ± 1.49b | 5.28 ± 1.96bc | |
| D-N0 | Dongfu 4 | 0 | 900.67 ± 219.00d | 13.53 ± 1.76c | 210.21 ± 61.08c | 52.21 ± 5.57a | 25.31 ± 2.62ef | 22.33 ± 3.85a | 6.16 ± 0.67a | 2.51 ± 0.15a |
| D-N1 | 50 | 684.00 ± 154.28c | 19.32 ± 1.55e | 351.85 ± 34.32d | 60.57 ± 2.67cd | 27.39 ± 1.55f | 28.65 ± 3.95c | 10.72 ± 2.1ab | 2.94 ± 0.24ab | |
| D-N2 | 100 | 490.00 ± 43.59b | 17.00 ± 1.61d | 298.84 ± 39.32d | 76.03 ± 3.75f | 27.47 ± 4.18f | 27.08 ± 3.00abc | 8.70 ± 1.40ab | 3.11 ± 0.39ab | |
| D-N3 | 150 | 465.67 ± 55.82b | 13.17 ± 2.10c | 196.70 ± 30.76bc | 58.40 ± 2.92bcd | 26.67 ± 4.48f | 31.55 ± 2.35cd | 11.29 ± 0.98ab | 3.11 ± 0.65ab | |
| E-N0 | En 1282 | 0 | 60.00 ± 0.33bcd | 5.57 ± 1.15a | 23.02 ± 3.11ab | 12.37 ± 0.56b | 6.02 ± 0.57c | |||
| E-N1 | 50 | 55.27 ± 1.36ab | 7.44 ± 0.70a | 26.60 ± 57.07abc | 27.77 ± 3.51c | 10.32 ± 2.02e | ||||
| E-N2 | 100 | Without nodule | 60.88 ± 1.06cd | 7.23 ± 1.32a | 28.78 ± 4.50c | 47.75 ± 7.16d | 7.68 ± 2.23cd | |||
| E-N3 | 150 | 61.31 ± 1.26cd | 13.92 ± 4.18b | 34.30 ± 3.79d | 32.40 ± 4.35c | 9.74 ± 3.00de | ||||
Data are mean ± standard variation (n = 3). Different lowercase letters in the same column show significant differences between treatments (P < 0.05). “H, D, E” represent the soybean cultivars “Heihe 38, Dongfu 4 and En1282” and “N0, N1, N2, N3” represent the four levels of N as urea, “0 N fertilizer; 50 mg N/kg soil; 100 mg N/kg soil; 150 mg N/kg soil”.