The Effects Of Nitrogen Application On CO₂ And N₂O Emission Flux In The Growing Season Of The Maize Field

In order to understand how nitrogen(N)fertilization application affects the CO₂ and N₂O emission flux in a maize field during the growing season, this field experiments were located in a maize field in Liangzhou, Wuwei City, Gansu Province. Three N levels were selected, they are: no N fertilizer (N0), 300kg-N?hm^-2(N300) and 450kg-N?hm^-2 (N450).The CO₂ and N₂O emission flux in a maize were observed continuously by using soil respiration measurement systerm and static enclosed chamber–GC/MS technique from maize Seedling to Maturity stage.The mechanism between soil temperature, soil water content and the CO₂ and N₂O emission flux was discussed, and the effects N fertilization application on maize plants, ear and yield were also studied. The main results showed as following:1. CO₂ emission flux of maize field under three N levels showed similar diurnal variation to soil temperature with single maxima during daytime from maize Seedling to Maturity stage. Diurnal variation showed N450> N300> N0, which explain that the higher N levels, the more soil respiration rate and CO₂ emission flux. The diurnal changes showed that more significantly in Filling and Maturity stage than Seedling and Elongation stage. The order of seasonal changes of CO₂ emission flux in the maize field followed as: Tasseling stage>Big-trumpet stage>Elongation stage>Filling stage>Maturity stage>Seedling stage.The seasonal changes of CO₂ emission flux showed that more significantly in Tasseling and Filling stage than in Seedling and Elongation stage, which explained that the effects N levels on CO₂ emission flux was more significantly in the latte of maize growth.2. N₂O emission was flux throughout the growing period of maize. Consistent with the CO₂, N₂O emission flux of maize field under three N levels showed similar diurnal variation to soil temperature with single maxima during daytime during the whole growing period. Diurnal variation showed N450> N300> N0, the changes was significant in whole growth season except in Mature stage. The order of seasonal change of N₂O emission flux in the maize field followed as: Big-trumpet stage>Seedling stage> Tasseling stage> Elongation stage>Filling stage>Maturity stage.Analysis showed that the effects N levels on N₂O emission flux was more significantly in the early and mid than in the latte of maize growth, espceial in Seedling and Big-trumpet stage. 3.Correlation analysis showed that there was signifieant positive correlation between CO₂ and N₂O emission flux and soil temperature in 0cm and 5cm(p<0.01), and correlation analysis also showed that there was significant correlation between CO₂ and N₂O emission flux and soil temperature in 10cm(p<0.05). CO₂ and N₂O emission flux under different N levels increased with the increasing temperature. The effects soil water content on CO₂ and N₂O emission flux of maize field were more complex during the maize whole growing season. Analysis showed that there was no direct relationship between them. CO₂ and N₂O emission flux were increased with increasing soil water content under water are in the appropriate conditions. But CO₂ and N₂O emission flux were reduced with increasing soil water content when the soil water reached a certain saturation range.4. Stem diameter, plant height, ear height, ear length and biological and economic yield of maize under different N levels conditions showed that N450> N300> N0, which increased with increasing N fertilizer.But ear coefficient and bald length showed that N0> N300> N450, which decreased with increasing N fertilizer. Variance analysis showed that the differences of biological and economic yield on the three treatments are significant, and N affected the maize growing season and the accumulation of yield of maize.