| Rising global temperature and frequently occurred extreme weather-climate event arouse people’s concern towards the tremendous impact human caused on global environment change. Numerous researches on climate change have proved that increasing greenhouse gases concentration in atmosphere account for the global warming occurred. Thus, exploring greenhouse gases emission mechanism is vital for the control of human-induced emission source. Farmland supplies human being with food and industrial material, but an important gases emission source also. Plastic mulching is a technique which has been widely adopted in rainfed farming areas, but research on greenhouse gases emission of fields with plastic mulching, however, is not deeply investigated. In the present study, maize field with plastic mulching in typical rainfed area-loess plateau was chosen to investigate the effect of plastic mulching on nitrous oxide flux, diurnal variation and concentration in different soil depth. Nitrous oxide (N2O) concentration was determined using chamber-gas chromatography method, and flux was then calculated. Combining with other data obtained, such as aboveground biomass, soil temperature and soil ammonium and nitrate content, further analysis was conducted. Some major conclusion can be drawn as follows:1. Both urea application and plastic mulching stimulate maize aboveground biomass accumulation. But the different is that urea application reveal its stimulate effect at late growth stage. Treatments with plastic mulching exhibit its stimulate effect at the very beginning of the growth stage. In particular, the treatment, two ridges and furrow mulched by plastic film with urea application (DRM), present its advantage over other treatments, both mulching and non-mulching.2. N2O flux diurnal variation showed different pattern according to the weather condition. In typical sunny days (June14th-15th and August28th-29th), soil N2O flux showed a two-peak curve, with one flux peak around12:00and the other around3:00. In a cloudy and rainy day, soil N2O flux reached the lowest point at around12:00-15:00and showed no flux peak.3. Soil N2O concentration monitoring result showed that:on May20th, the first soil N2O concentration determination, N2O concentration in0-10cm ridge soil of the treatment alternating ridges and furrows mulched by plastic film with urea application (MINI) was747.3138ppb, which is significantly higher than DRM (539.4266ppb). The concentration of DRM is higher than all other treatments left with a significance at p<0.05. Henceforth N2O concentration in0-10cm soil decreased gradually. Around June15th, all treatment kept an N2O concentration about325-350ppb, and kept at this level until harvesting.4. N2O flux was monitored in partial of the growth period. No seasonal variation was observed in the test period. On the whole, N2O flux of all treatments decreased gradually until reached the lowest point, afterwards, flux of all treatments increased and reached the highest point around harvesting. A week after harvesting, N2O flux decreased sharply. On June9th, the first N2O flux determination, DRM N2O flux was significantly higher M1N0and M0N1. On June15th, DRM N2O flux was significantly higher than all the other treatments. Afterwards, N2O flux difference among treatments diminished.5. Correlation analysis between0-10cm soil temperature and soil N2O flux proved that:in typical sunny days, soil temperature showed a significant negative linear correlation with N2O flux. While, in cloudy and rainy day, soil temperature showed a significant negative exponential correlation with N2O flux. Correlation analysis between0-10cm soil temperature and20-30cm soil N2O concentration proved that:soil temperature showed a significant positive linear or exponential correlation with20-30cm soil N2O concentration.20-30cm soil N2O concentration showed a significant positive correlation with N2O flux. During the test period, plant available nitrogen content (soil nitrate and ammonium content) showed a significant exponential correlation with20-30cm soil N2O concentration. |
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