Table 4.
The nitrogen source of rice plants and soil residual urea-15N in different treatments at maturity.
| Treatment | Grain |
Straw |
Root |
Soil (0–20 cm) |
N decline (kg ha-) | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Ndff (%) | Ndff (kg ha-) | Ndfs (kg ha-) | Ndff (%) | Ndff (kg ha-) | Ndfs (kg ha-) | Ndff (%) | Ndff (kg ha-) | Ndfs (kg ha-) | Ndff (kg ha-) | Ndff (%) | ||
| NBP | 20.3 c | 12.9 c | 51.0 c | 13.4 c | 4.3 c | 30.5 a | 8.6 a | 0.23 b | 2.9 a | 19.2 b | 0.43 a | 59.2 a |
| NDP | 33.7 b | 39.2 b | 77.2 a | 32.6 b | 11.0 b | 22.8 a | 9.9 a | 0.74 ab | 6.2 a | 30.6 a | 0.60 a | 62.5 a |
| NPKDP | 46.5 a | 59.0 a | 68.0 b | 38.9 a | 14.1 a | 22.2 a | 10.7 a | 0.82 a | 7.9 a | 21.4 ab | 0.49 a | 60.1 a |
Ndff and Ndfs mean the N derived from fertilizer and soil; N decline (kg ha-1) is the soil N declined as a result of plant uptake. N decline = Ndfs in grain + Ndfs in straw – (Ndff + Ndfs) in root – Ndff in soil. Different letters means significant difference at the 0.05 probability level according to Duncan’s multiple comparison test.