| IIIMethane（CH4）is not only a major source of greenhouse gases but also able to cause greenhouse effect.CH4 and CO2 have the same molecule number,but CH4 has about 25 times potential to cause global warming than that of CO2,which seriously influences the human living environment.The rice field is an important source of CH4,therefore,how to reduce the CH4 emission of rice field is of great significance to mitigate the greenhouse effect.The study was conducted in the double cropping area of Guangdong Province,where belongs to typical subtropical monsoon humid climate zone.In this study,two typical patterns of no-tillage and conventional tillage treatments were set up,including conventional and no fertilization,conventional and fertilization,no tillage and no fertilization,no tillage and fertilization.The effects of no-tillage and fertilization on CH4 emission in early rice paddy field were explored.Meanwhile,the mechanisms of temperature,wind speed,humidity,soil organic matter,soil p H and soil enzyme activity on CH4 emission were also analyzed.The results are as follows:1.CH4 emission from paddy field at tillering stage showed obvious diurnal variation characteristics,and CH4 emission trends were similar among treatments.The emission peak appeared at 15:00 and the lowest emission appeared at 21:00.The daily average CH4 emission fluxes among treatments followed the decreasing order: conventional tillage and fertilizer（24.47 mg/m2·h）> conventional tillage and no fertilization（48.56 mg/m2·h）> no-tillage and fertilizer（1.97 mg/m2·h）> no-tillage and no fertilizer（8.88 mg/m2·h）.The diurnal variation characteristics of CH4 emission in paddy field at heading stage were not obvious,and the peak and the lowest value of CH4 emission were inconsistent among treatments.The daily emission flux of CH4 among treatments followed the decreasing order: conventional tillage and no fertilization（19.43 mg/m2·h）> no-tillage and fertilizer（6.06 mg/m2·h）> conventional tillage and fertilizer（5.34 mg/m2·h）> no-tillage and no fertilizer（4.67 mg/m2·h）.2.During the whole growth period,the CH4 emission under no-tillage treatment was lower than that of conventional tillage treatment.The dynamic change of CH4 emission in paddy field met the multi-peak model: the highest value of CH4 emission in paddy field appeared at the tillering stage,and the lowest value appeared in the sun field（41 days after transplanting）.The average emission flux of CH4 in paddy field during growth period followed the decreasing order: conventional tillage and no fertilization（25.68 mg/m2·h）> conventional tillage and fertilizer（19.55 mg/m2·h）> no-tillage and fertilizer（11.67 mg/m2·h）> no-tillage and no fertilizer（4.54 mg/m2·h）.The CH4 emission under no-tillage treatment was 64.16% lower than that of conventional tillage treatment.3.Soil enzyme activity increased under no-tillage treatment,which was beneficial to maintaining or improving soil fertility.Compared with the conventional tillage,the activities of urease and acid phosphatase were increased by 5.27%-10.85% and 5.26%-6.56% under no-tillage treatment respectively.The main effects of urinary enzyme activity at booting stage and heading stage were significant（P<0.05）,while the main effects of acid phosphatase activity at booting stage,heading stage and mature stage presented to be significant（P<0.05）.The results of soil nutrient assay showed that the soil organic matter,ammonium nitrogen and nitrate nitrogen under no-tillage treatment were higher than those under conventional tillage treatment.The soil organic matter content under no-tillage treatment was 4.00%-8.92% higher than that under conventional tillage treatment,and the main effects of soil organic matter at tillering stage,booting stage,heading stage and mature stage were significant（P<0.05）.The soil ammonium nitrogen content under no-tillage treatment was 16.50%-24.88% higher than that under conventional tillage treatment,and the main effects of soil organic matter at booting stage and heading date were significant（P<0.05）.The soil nitrate nitrogen content under no-tillage treatment increased by 17.73% compared with the conventional tillage treatment,and the main effects of maturity of soil nitrate nitrogen at booting stage,heading date and maturity stage were significant（P<0.05）.But no-tillage treatment in paddy field led to reduction of soil p H.4.The daily scale emission of CH4 in paddy field was positively correlated with air temperature,surface temperature,5 cm soil temperature,grass surface temperature,absolute humidity and wind speed under no-tillage and conventional tillage treatments.Soil p H,soil organic matter,soil ammonium content and soil urease activity were positively correlated with CH4 fluxes,and soil NO3-N content was not significantly correlated with CH4 emission in paddy field. |
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