Table 2.
Effects of different nitrogen fertilizer application rate on soil chemical and biological characteristics.
| Soil properties | N0 | N8 | N12 | N16 | N20 | N24 | F-value |
|---|---|---|---|---|---|---|---|
| pH | 8.25 ± 0.04a | 8.15 ± 0.04b | 8.15 ± 0.02b | 8.15 ± 0.0b | 8.11 ± 0.02b | 8.05 ± 0.02c | 12.966*** |
| SOC (g·kg-1) | 11.52 ± 0.69c | 12.63 ± 1.01b | 13.07 ± 0.06b | 15.29 ± 0.18a | 13.41 ± 0.57b | 13.3 ± 0.76b | 11.139*** |
| NH4 +-N (mg·kg-1) | 5.62 ± 0.21e | 5.82 ± 0.06de | 5.99 ± 0.09cd | 6.05 ± 0.08c | 6.36 ± 0.11b | 6.91 ± 0.16a | 34.594*** |
| NO3 –N (mg·kg-1) | 7.46 ± 0.07e | 9.13 ± 0.31d | 8.99 ± 0.05d | 9.67 ± 0.07c | 11.32 ± 0.02b | 26.17 ± 0.24a | 5044.785*** |
| MBC (mg·kg-1) | 323.6 ± 19.41c | 346.69 ± 5.41b | 388.86 ± 1.52a | 400.99 ± 7.74a | 365.01 ± 5.28b | 359.03 ± 2.75b | 28.167*** |
| MBN (mg·kg-1) | 69.51 ± 1.52d | 73.72 ± 1.35c | 75.32 ± 2.15bc | 80.06 ± 1.45a | 77.45 ± 1.26b | 74.86 ± 0.54c | 17.774*** |
| S-NiR (umol·(d-1·g-1)) | 0.99 ± 0.13d | 1.54 ± 0.31c | 2.09 ± 0.02c | 2.21 ± 0.08a | 1.66 ± 0.11b | 1.622 ± 0.2c | 18.826*** |
| S-NR (ug·(d-1·g-1)) | 10.3 ± 1.27d | 12.6 ± 0.64c | 13.37 ± 0.37b | 15.52 ± 0.95a | 14.58 ± 0.57bc | 12.621 ± 0.16bc | 17.066*** |
| ALPT (mg·(d-1·g-1)) | 0.1155 ± 0.011c | 0.3489 ± 0.053b | 0.4149 ± 0.011a | 0.5847 ± 0.053a | 0.297 ± 0.010b | 0.1792 ± 0.03b | 74.234*** |
| HR (ug·(d-1·g-1)) | 997.34 ± 7.21d | 1023.86 ± 12.94c | 1050.81 ± 3.54bc | 1092.78 ± 25.66a | 1043.95 ± 18.43b | 1043.145 ± 25.27c | 9.601** |
| UE (ug·(d-1·g-1)) | 1768.88 ± 32.1e | 2115.97 ± 92.13c | 2344.54 ± 98.54b | 2539.25 ± 286.3a | 2255.65 ± 48.31c | 2285.289 ± 58.15d | 11.357*** |
SOC, soil organic carbon; MBC, microbial biomass carbon; MBN, microbial biomass nitrogen; NO3–N, nitrate nitrogen; NH4 +-N, ammonium nitrogen; S-NiR, Soil enzymes include soil nitrite reductase; S-NR, soil nitrate reductase; alkaline protease; HR, hydroxylamine reductase; UE, urease. ** means P<0.01; *** means P<0.001.