Mitigation Options Of CH4 And N2O Emissions From Rice Fields

CH4 and N2O are two important greenhouse gases which just second to CO2. Rice field ecosystems is considered to be a crucial source of CH4 and N2O emission. In order to select mitigation measurements for reducing greenhouse gas emissions in paddies, this research was divided into two parts, one was an integration analysis of CH4 and N2O emissions from rice field in China, the another was field experiment measurement. By using the method of static chamber-gas chromatograph techniques, CH4 and N2O emission fluxes from double rice fields were measured under two field experiments including different nitrogen and phosphate fertilizer amount and organic inorganic fertilizer treatments.The main results are presented as follows:1. Integration analysis of database about CH4 and N2O emissions from rice field in China(1)There existed a zonal distribution law for CH4 emission in China, which showed that the CH4 emissions from Southwest China was far more than other rice planting area. The zonal distribution law for N2O emission was not clearly.(2)Water management regimes including rice growing period and non-rice growing season were important factors controlled CH4 emission. Compared to continuously flooded (F), flooding-midseason drainage-reflooding(F-D-F), flooding-midseason drainage-reflooding-moist intermittent irrigation, but without water logging(F-D-F-M)and alternative flooding and drainage after transplanting, or moister irrigation but without water logging(M)reduced CH4 emission by 45%, 59% and 83%, respectively. The mode of short drainage (SD), long drainage (LD), and two drainage (TD) could reduce 42% ~56 % compared to flood (F).(3)Types of synthetic nitrogen fertilizer or organic amendments and levels of chemical nitrogen fertilizer amount affected CH4 emission significantly. Simulated effect of organic amendments on CH4 emission from rice field was decreased by order of that, crop straw + farm manure(S+FM) > green manure (GM) > farm manure(FM) > crop straw(S) > composted farm manure and biogas digestion(CM). The effect of different types of chemical nitrogen fertilizer on CH4 emission was controversial to some experiment results. The CH4 emission was decreasing gradually with increasing chemical nitrogen fertilizer ratio (N). When N was 0< N≤150 kg N ? hm-2,150< N <250 kg N ? hm-2 and N≥250 kg N ? hm-2,CH4 emission was reduced by 12%,29% and 65% compared with treatment of non-fertilizer.(4)The factors including water management regimes in rice growing period, the non-rice season water status, and total nitrogen fertilizer input were important factors for N2O emission. Compared to CF, the N2O emission was increased by 12%, 140% and 478% under F-D-F, F-D-F-M and M. The nitrogen fertilizer-induced N2O emission factors were estimated to be 0.43% and 0.68% for F-D-F and F-D-F-M, respectively. By analyzing of water status of non-rice growing season, the average N2O emission rise to 40% ~110% under SD, LD and TD, compared to F.2. Field experiments measurement(1)Chemical fertilizer treatment enhanced CH4 emission in period of seeding establishment by analyzing different growing season stage in double rice. All treatments including non-fertilization were found not significant difference by statistics. N2O emission was weakly relative to input N amount in double rice fields.(2)When input total N amount was equal, adoption of mushroom residue(MR+NPK1)reduced CH4 emissions by 46% and 68% and increased N2O emissions. by 57% and 8% compared with fresh rice straw(RS+NPK1)in early and late rice field; using biogas digestion(BD+NPK2)reduced CH4 emissions by 56% and 65% and increased N2O emissions by 63% and 179% compared with fresh cow dung(BD+NPK2)in early and late rice field.(3)CH4 product ability of organic materials has closed relationship with easily decomposable organic carbon content. The theory of C / N ratio regulation on N2O production of organic materials was suited to apply to the types of organics which have a great gap in C / N ratio. For organic materials of C / N ratio closely, the composition of nitrogen form and organic carbon may be play more important function than C / N ratio.(4)Mid-season drainage was decisive for CH4 emission. Meanwhile, N2O emission was very weak during in this period, There was not exited a trade-off relationship between CH4 and N2O emission in water regime.(5)Nitrogen and phosphate fertilizer amount has little effect on total global worming potential of double rice field, but it has great influence on grain yield; Grain yield was not found significant difference under organic and in organic fertilizer treatment, but there were a great differences between their total global worming potential. CH4 was the dominated greenhouse gas in local double rice field, so the mitigation measurements should focus on how to reduce CH4 emission. On aspect of fertilizer managements, we can adopt strategy that taken highest yield and lowest total global worming potential as indicators to choose inorganic fertilizer amount and organic fertilizer types.