Table 4.
Rice growth parameters at time of harvest (including plants that had died) from field exposures conducted during the 2012 dry 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 | 0.17 (0.05) | 12.50 (0.89) | 20.87 (3.80) | 5.20 (1.42) | 88.80 (2.03) | 13.29 (2.33) |
| 60 | 0.23 (0.22) | 19.67 (1.74) | 25.65 (3.28) | 11.36 (2.63) | 82.28 (3.21) | 23.42 (3.05) | |
| 150 | 0.30 (0.26) | 20.00 (1.46) | 36.57 (5.08) | 13.62 (3.22) | 70.63 (8.37) | 19.80 (3.54) | |
| IR62 | 0 | 0.09 (0.09) | 12.50 (1.26) | 17.65 (1.96) | 4.78 (0.96) | 75.72 (4.07) | 14.04 (1.66) |
| 60 | 0.20 (0.11) | 19.50 (1.06) | 26.46 (2.74) | 8.70 (1.52) | 78.79 (1.27) | 19.65 (3.32) | |
| 150 | 0.11 (0.09) | 26.00 (0.06) | 34.12 (4.60) | 15.45 (3.31) | 74.90 (5.45) | 31.20 (5.36) | |
| Infested | |||||||
| IR22 | 0 | 174.12 (47.88) | 8.17 (1.74) | 16.11 (2.23) | 2.53 (0.69) | 25.23 (17.32) | 1.47 (1.15) |
| 60 | 140.56 (33.60) | 7.67 (3.52) | 24.17 (4.68) | 1.70 (0.79) | 28.61 (14.35) | 5.21 (2.50) | |
| 150 | 139.59 (32.94) | 9.50 (4.30) | 31.26 (3.09) | 6.15 (3.32) | 27.41 (9.81) | 2.92 (1.41) | |
| IR62 | 0 | 52.17 (19.52) | 16.67 (1.96) | 14.94 (1.99) | 7.04 (1.36) | 68.86 (5.94) | 15.64 (3.12) |
| 60 | 19.68 (12.57) | 22.00 (1.41) | 27.77 (2.76) | 8.36 (1.19) | 75.64 (4.71) | 21.74 (1.68) | |
| 150 | 31.04 (11.65) | 27.33 (1.82) | 29.00 (4.45) | 14.20 (3.33) | 72.12 (4.97) | 30.74 (4.55) | |
| F-nitrogen (N)c | 0.126 ns | 2.768 ns | 4.037* | 2.189 ns | 0.199 ns | 2.232 ns | |
| (Linear contrast)c | 0.694 ns | 15.223*** | 12.281*** | 0.915 ns | 15.223*** | 22.223*** | |
| F-control/infested (I)c | 31.102*** | 3.579 ns | 1.392 ns | 3.496 ns | 41.896*** | 10.273** | |
| F-variety (V)c | 12.441** | 21.816*** | 0.093 ns | 3.081 ns | 21.364*** | 24.103*** | |
| F-N × Vc | 0.016 ns | 1.819 ns | 0.343 ns | 0.325 ns | 0.362 ns | 3.487* | |
| F-N × Ic | 0.383 ns | 0.849 ns | 0.357 ns | 0.776 ns | 0.616 ns | 0.232 ns | |
| F-V × Ic | 12.397** | 12.242** | 0.107 ns | 3.995 ns | 30.570*** | 13.539** | |
| F-N × V × Ic | 0.017 ns | 0.274 ns | 0.023 ns | 0.144 ns | 0.257 ns | 0.189 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.