Table 3: Effects of tillage, N application and different seasons on Δ13C values (%) of wheat anthesis dry matter*.
| Year | Conventional till (CT) | No-till (NT) | Year mean | ||
| No N added (N0) | 75 kg N ha-1 (N75) | No N added (N0) | 75 kg N ha-1 (N75) | ||
| 1992 | 15.54 | 15.43 | 16.44 | 16.04 | 15.86 |
| 1993 | nd | nd | nd | nd | nd |
| 1994 | 16.42 | 15.41 | 16.46 | 15.52 | 15.95 |
| 1995 | 15.34 | 14.95 | 16.17 | 15.54 | 15.50 |
| 1996 | 17.37 | 16.70 | 17.23 | 16.66 | 16.99 |
| Mean | 16.17 | 15.62 | 16.58 | 15.94 | 16.08 |
*Treatment effects: least significant difference at P < 0.05; year, 0.26; tillage, 0.22; N, 0.22; year × tillage, 0.37; year × N, 0.37. Tillage × N and year × tillage × N interactions were not significant.