Table 2.
N concentration, C:N ratio and 15N abundance in shoot and root of field pea grown for 15 weeks under either an aCO2 or eCO2 concentration and with 5, 25, 50 or 90 mg NO3–-N kg–1 soil
| Factor | N rate (mg kg–1) | N concentration (g kg–1) |
C:N |
15N (atom%) |
||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Shoot | Root1 | Root2 | Shoot | Root1 | Root2 | Shoot | Root1 | Root2 | ||
| N rate (mg kg–1) | 5 | 20·7 | 24·3 | 29·3 | 20·4 | 16·3 | 14·0 | 1·6 | 1·2 | 2·5 |
| 25 | 20·3 | 24·3 | 29·5 | 20·8 | 16·1 | 14·1 | 6·0 | 4·1 | 7·4 | |
| 50 | 21·9 | 22·3 | 29·3 | 20·7 | 16·9 | 14·1 | 2·6 | 2·0 | 2·9 | |
| 90 | 20·5 | 24·2 | 29·2 | 20·7 | 16·4 | 13·6 | 3·1 | 2·4 | 3·3 | |
| CO2 level | aCO2 | 20·8 | 24·1 | 30·1 | 20·1 | 16·0 | 13·4 | 3·8 | 2·7 | 4·3 |
| eCO2 | 20·9 | 23·4 | 28·5 | 21·3 | 16·8 | 14·6 | 2·9 | 2·2 | 3·8 | |
| N rate | n.s. | n.s. | n.s. | n.s. | n.s. | n.s. | *** | *** | *** | |
| LSD (P = 0·05) | – | – | – | – | – | – | 1·08 | 0·32 | 0·63 | |
| CO2 level | n.s. | n.s. | n.s. | n.s. | n.s. | n.s. | * | * | * | |
| LSD (P = 0·05) | – | – | – | – | – | – | 0·72 | 0·30 | 0·30 | |
Roots from 0–10 cm (root1) and 10–55 cm (root2) were analysed separately.
No CO2 × N interactions were observed (P > 0·05).
n.s., P > 0·05; *P < 0·05; ***P < 0·001.
–, not applicable; LSD, least significant difference