Abstract: This study aimed to clarify the effects of different N application rates and light intensities on N₂O emission flux in phyllosphere and rhizosphere of rice and its mechanism. The experiment was carried out by hydroponic method in a small light-controlled incubator, using rice variety Peizataifeng as the material, and the above-ground and underground parts of rice were strictly separated in the inner and outer chambers of the test device. The amount of N₂O emitted from the root and leaf interface of rice was determined by gas chromatography. First, we conducted the indoor low light (8:00-18:00, 4 000 lx) test using NH₄NO₃ as the nitrogen source, of which three N levels, low nitrogen (30 mg/L), medium nitrogen (60 mg/L) and high nitrogen (90 mg/L) at different developing stages were arranged. On this basis,we carried out the experiment under the conditions of low light (4 000 lx), strong light (8 000 lx) and natural light, including three N treatments:denitrification (0 mg/L), low nitrogen (30 mg/L) and high nitrogen (90 mg/L) at flowering and fruiting stages. The results showed that, under weak illumination (8:00-18:00, 4 000 lx), the mean rate of N₂O emission was 34.9, 42.4 and 98.3 μg/(m² · h) in rice phyllosphere, and was 29.6, 79.6, 246.1 μg/(m² · h) in rice rhizosphere, respectively, for treatments of 1N (30 mg/L), 2N (60 mg/L) and 3N (90 mg/L). With the increase of N rate, the amount of N₂O emission in rice phyllosphere and rhizosphere also increased (P<0.05), and the similar results were obtained at flowering/seeding stage and mature aging stage. The N₂O emission rate in the phyllosphere of 0N (0 mg/L), 1N (30 mg/L) and 3N (90 mg/L) was 2.9, 29.1 and 116.3 μg/(m² · h) for weak light treatment, was 23.6, 40.1 and 120.1 μg/(m² · h) for strong light treatment (8:00-18:00, 8 000 lx), and was up to 10.9, 26.2 and 131.3 μg/(m² · h) under natural light,condition, respectively. The N₂O emission rate in the rhizosphere of 0N (0 mg/L),1N (30 mg/L) and 3N (90 mg/L) was 3.3, 77.1 and 308.4 μg/(m² · h) for weak light treatment, was 14.1, 45.6, and 182.4 μg/(m² · h) for strong light treatment, and was 19.3, 44.9 and 224.6 μg/(m² · h) under natural light,condition, respectively. Under strong and natural light conditions, the N₂O emission rate in the rhizosphere of rice was not significant between 0 N (0 mg/L) and 1N (30 mg/L) treatments (P>0.05). Under weak light condition, the N₂O emission rate in the rhizosphere and phyllospher increased with the increase of N application amount. Under the same condition of N application (1N, 3N), the N₂O emissions in the rhizosphere of rice could be inhibited by stronger light and sunlight compared with the results of weak light treatment. It was suggested that the combination of strong light and low N level (1N) could inhibit the N₂O emissions in the rhizosphere and phyllosphere of rice.

Key words: Illumination, Nitrogen application rate, Rice, Phyllosphere, Rhizosphere, N₂O, Emissions

CLC Number: 

• S153.6

• X511