TABLE 5.
Effect of nitrogen (N) application rates on grain yield, N fertilizer recovery, N fertilizer contribution efficiency, N fertilizer partial factor productivity and agronomic efficiency of N fertilizer in winter wheat during 2018 and 2019.
| Year | Treatment | Grain yield (kg⋅hm−2) | N harvest index | N-fertilizer recovery efficiency (kg kg–1) | Nitrogen fertilizer contribution rate (%) | N-fertilizer partial factor productivity (kg kg–1) | Agronomic efficiency of N-fertilizer (kg kg–1) |
| 2018 | N0 | 5186.61d | 0.897a | / | / | / | / |
| N75 | 6006.38c | 0.890ab | 32.67b | 15.05c | 80.09a | 12.50a | |
| N150 | 6490.00b | 0.880ab | 42.23ab | 21.26b | 43.02b | 9.18b | |
| N225 | 6600.00a | 0.874b | 55.41a | 22.69a | 29.33c | 6.66bc | |
| N300 | 6550.00b | 0.816c | 44.91a | 21.62b | 21.70d | 4.69c | |
| 2019 | N0 | 4104.16d | 0.873a | / | / | / | / |
| N75 | 5254.69c | 0.864ab | 38.12a | 21.88c | 70.06a | 15.34a | |
| N150 | 6500.86b | 0.859ab | 39.57a | 36.82ab | 43.34b | 15.98a | |
| N225 | 6845.47a | 0.853ab | 44.91a | 40.02a | 30.42c | 12.18b | |
| N300 | 6405.68b | 0.831b | 34.61a | 35.88b | 21.35d | 7.67c |
N0: unfertilized control; N75: N application at 75 kg N⋅ha–1; N150: N application at 150 kg N⋅ha–1; N225: N application at 225 kg N⋅ha–1; N300: traditional N application rate of 300 kg N⋅ha–1. Different small letters show significant differences at p < 0.05.