The Effects Of Different Tillage Treatments On CO₂ And N₂O Emission Flux In The Winter-Wheat Field

Field experiments were conducted in 2007-2008 to study the effects of different conservation tillage systems, including conventional tillage (T), conventional tillage with stubble incorporating (TIS), no-tillage without stubble retention (NT), no-tillage with stubble standing (NTSS), no-tillage with stubble retention (NTS), on the CO₂ and N₂O emission flux from filling stage in last season to tiller stage in next season, soil water content, soil temperature, soil strength, soil bulk density, and grain yield of winter wheat in Gansu Agricultural University Experiment Station. The mechanism between soil water content, soil temperature, soil strength, soil bulk density, and CO₂ and N₂O emission flux of different conservation tillage systems was also discussed. The results showed that:1 .Tillage systems can affect CO₂ emission flux of winter wheat field. Compared to conventional tillage (T), no-tillage without stubble retention (NT) significantly improved CO₂ emission flux by 37.63%-152.03% at every measurement stage, and compared to no-tillage without stubble retention (NT), no-tillage with stubble standing (NTSS), and no-tillage with stubble retention (NTS) treatments, conventional tillage with stubble incorporating (TIS) improved CO₂ emission flux by 41.63%-216.70%, 8.29%-154.27%, and 16.49%-85.96%, respectively, but significant differences were only found between TIS, NT, and NTS treatments. At every measurement stage, CO₂ emission flux of conventional tillage with stubble incorporated (TIS) was biggest among all treatments. Therefore, NTS, NTSS, and NT treatments can decrease CO₂ emission flux.2.Correlation analysis showed that there was significant positive correlation between CO₂ emission flux and soil temperature in 0cm, 5cm, 10cm, and 20cm soil depth, and correlation analysis also showed that there was significant positive correlation between CO₂ emission flux and soil water content in 0-10cm, 10-20cm, and 20-30cm soil layer. Correlation analysis showed that there was negative correlation between CO₂ emission flux and soil bulk density in 0-10 cm, 10-20cm, and 20-30cm soil layer, but significant differences were only found between CO₂ emission flux and soil bulk density in 0-10 cm and 10-20cm soil layer. In a word, CO₂ emission flux has close relationships with soil water content and soil temperature.3. Tillage systems can affect N₂O emission flux of winter wheat field. At every measurement stage, T treatment decreased N₂O emission flux by 5.51%-41.53% compared with NT treatment, and compared to NT, NTSS, and NTS treatments, TIS treatment improved N₂O emission flux by 12.24%-94.87%, 3.18%-30.52%,1.31%-29.06%, and 26.57%-175.81%, respectively. Compared to NTSS and NTS treatments, NT treatments decreased N₂O emission flux by 4.90%-50.14% and 10.79%-51.00%. Therefore, TIS,NTS,NTSS, and NT treatments improved N₂O emission flux compared to T treatment, and N₂O emission flux of TIS treatment was biggest among all treatments. In a word, NTS, NTSS, and NT treatments did not decrease N₂O emission flux, but significantly increased decrease N₂O emission.4.Correlation analysis showed that there were significant negative correlations between N₂O emission flux, soil temperature, and soil water content, but correlation analysis showed that there was positive correlation between N₂O emission flux and soil bulk density, and significant correlation were only found between N₂O emission flux and soil bulk density in 10-20cm soil layer. In a word, N₂O emission flux has closer relationships with soil water content and soil temperature, and soil water content more greatly affected N₂O emission flux than soil temperature, and the relationship between N₂O emission flux and soil bulk density was not close.5.NT, NTSS, and NTS treatments improved yield of winter wheat. Compared to T treatment, NT,NTS and NTSS treatments improved yield by 5.88%, 1.89%, and 15.65%, respectively, and improved yield by 11.29%, 6.98% and 2.94%, respectively, compared to TIS treatment. During the whole measurement stage, compared to NT, NTS, and NTSS treatments, T treatment improved average CO₂ emission flux 48.99%, 64.62%, and 17.42%, respectively, TIS treatment improved average CO₂ emission flux by 29.73%, 14.65%, and 26.67%, respectively. Compared to TIS, NT, NTS, and NTSS treatments, T treatment decreased average N₂O emission flux by 49.68%, 14.86%, 37.91%, and 33.38%, respectively, but TIS improved N₂O emission flux by 30.31%, 8.54%, and 12.22%, respectively, compared to NT, NTS, and NTSS treatments. Generally speaking, NTS, NTSS, and NT treatments improved yield of winter wheat and water use efficiency, and also increased N₂O emission flux, but decreased soil water consumption and CO₂ emission flux. Comparatively speaking, no-tillage without stubble retention (NT) is one kind of best tillage system which can not only improve grain yield but also protect environment. In a word, many factors affect CO₂ emission flux and N₂O emission flux, but the comprehensive effect of these factors on CO₂ emission flux and N₂O emission flux was not simple additive effect of these factors, but was overall embodiment of many comprehensive effects.