Table 3.
Rice growth parameters at time of harvest (including plants that had died) from field exposures conducted during the 2011 wet season. Planthopper biomass density is indicated from field cages infested with laboratory reared Nilaparvata lugens (infested) and cages colonized by wild N. lugens (control).
| Treatment (infestation and variety) | Nitrogen level (kg ha−1)a | Planthopper biomass density (mg g-plant−1)b | Number of tillersb | Shoot biomass (g dry weight)b | Root biomass (g dry weight)b | Percentage filled grainb | Biomass of filled grain (g dry weight)b |
|---|---|---|---|---|---|---|---|
| Control | |||||||
| IR22 | 0 | 0.07 (0.02) | 18.00 (1.86) | 17.78 (2.68) | 5.69 (1.24) | 75.36 (15.14) | 23.37 (5.43) |
| 60 | 0.13 (0.08) | 24.33 (1.58) | 21.83 (5.03) | 6.30 (1.66) | 80.61 (4.04) | 22.53 (2.70) | |
| 150 | 0.13 (0.09) | 27.83 (3.20) | 36.58 (9.28) | 12.05 (3.72) | 76.70 (3.70) | 30.30 (5.64) | |
| IR62 | 0 | 0.01 (0.01) | 21.50 (2.31) | 24.94 (2.91) | 6.00 (0.83) | 78.63 (2.42) | 32.84 (5.07) |
| 60 | 0.04 (0.03) | 22.50 (2.83) | 28.09 (6.48) | 5.92 (1.51) | 81.64 (2.31) | 31.35 (4.46) | |
| 150 | 0.02 (0.01) | 23.33 (4.02) | 43.04 (9.13) | 12.95 (2.94) | 77.51 (8.34) | 31.85 (6.46) | |
| Infested | |||||||
| IR22 | 0 | 6.86 (1.95) | 7.00 (3.27) | 12.00 (2.32) | 2.72 (0.64) | 52.66 (16.36) | 3.67 (2.72) |
| 60 | 5.47 (1.29) | 3.83 (3.83) | 14.35 (4.27) | 3.13 (0.80) | 57.76 (0.00) | 1.24 (1.24) | |
| 150 | 7.34 (2.54) | 5.67 (4.27) | 22.40 (5.07) | 5.83 (0.87) | 37.32 (21.36) | 2.10 (1.94) | |
| IR62 | 0 | 0.27 (0.26) | 15.50 (1.52) | 23.01 (5.33) | 4.96 (0.74) | 84.59 (2.00) | 22.81 (3.90) |
| 60 | 1.18 (1.14) | 27.83 (4.56) | 19.83 (3.22) | 6.00 (1.10) | 82.01 (3.44) | 26.13 (7.04) | |
| 150 | 0.06 (0.03) | 35.00 (4.09) | 38.82 (4.57) | 9.03 (2.25) | 82.27 (1.22) | 50.44 (6.86) | |
| F-nitrogen (N)c | 0.006 ns | 0.893 ns | 2.938 ns | 0.383 ns | 0.245 ns | 0.667 ns | |
| (Linear contrast)c | 0.031 ns | 4.910** | 16.160*** | 2.106* | 1.030 ns | 3.668* | |
| F-control/infested (I)c | 18.625*** | 7.277* | 4.844* | 6.754* | 3.796 ns | 8.103** | |
| F-variety (V)c | 14.653** | 13.915** | 5.314* | 5.319* | 8.021* | 23.517*** | |
| F-N × Vc | 0.319 ns | 0.550 ns | 0.169 ns | 0.454 ns | 0.482 ns | 0.692 ns | |
| F-N × Ic | 0.021 ns | 0.135 ns | 0.296 ns | 0.675 ns | 0.303 ns | 0.655 ns | |
| F-V × Ic | 13.808** | 16.716*** | 0.583 ns | 5.181* | 6.520* | 9.828** | |
| F-N × V × Ic | 0.313 ns | 2.657 ns | 0.103 ns | 0.952 ns | 0.488 ns | 2.206 ns | |
Nominator df = 2 (nitrogen – main plot), 1 (infested/control), 1 (variety), 2 (N × V), 2 (N × I), 1 (V × I), 2 (N × V × I); denominator df = 71 (split–split plot design).
a
Plants with 0 added nitrogen had low residual, background nitrogen levels in the soil. These were not determined during the experiment.
b
Numbers in parentheses are standard errors (N = 6).
c
ns = P > 0.05.
*
=P ≤ 0.05.
**
=P ≤ 0.01.
***
=P ≤ 0.001.