Research On The Characters Of N₂O Emission From The Farmland In The Hilly Area, Chongqing

N₂O is a serious greenhouse gas and the research on the characters of N₂O emission from different soils has got extensively attention. At present, the experimental plots are very limited in China, such as meadow brown soil in Shenyang, semiarid grassland in Inner Mongolia, the area of Lake Tai in Jiangsu and the highland paddy area in the central Sichuan Basin et al., which has got some outcomes but we still can not make a rude estimation on the N₂O emission because of the few soil types in China , so it is very meaningful to make research on the N₂O emission from important soil types.Basing on the observation of N₂O emission from two typical farmland in the hilly area, Chongqing, and arrangement for four treatments in each expenrimental plots (bare soil shorting for NPNF, plant and no fertilizer shorting for PNF, plant and chemical fertilizer shorting for PCF, and plant and chemical fertilizer and manure shoring for PCFM), the seasonal variation characteristic of N₂O emission and the influence of environmental factors were discussed. N₂O emission was measured by static chamber-gas chromatographic techniques (GC) . The main results and conclusions were listed as follows:(1) N₂O flux from farmland in the hilly area, Chongqing, has a significant seasonal variation characteristic along with the changing of temperature, and the proportion of the total N₂O emission in summer accounting for the annual one in the two experimental spots separately are about 52% for the purple soil and about 62% for yellow soil;(2)Temperature markedly affects the N₂O production and emission, and the relationship betweenN₂O emission and soil temperature in 5 cm is power function except for bare soil, and the markedlevel is 0.01 in the plot of purple soil, and about 73% of the significant N₂O emission(>0.035mg/m²Ã‚·h) happens when the soil temperature in 5 cm is above 25℃; and 33% of the significant from yellow soil happens while 20℃-25℃and the partial correlation coefficient between N₂O emission and soil temperature in 5 cm has got to the most significant level;(3) Soil water content has a complicated influence on the N₂O output from purple soil and about 75% of the significant N₂O emission (>0.035mg/m²*h) happens when the range of soil water content is 14-21% ( accounting for 52%-80% field capacity ) ; for yellow soil the N₂O emission and soil water content has a linear relationship in the treatment of only plant and no fertilizer, logarithmic( P<0.05 ) for the treatment of plant and chemical fertilizer (PCF), and the significant N₂O emission happens under the condition of soil water content is 14-25%;(4)The partial correlation coefficient between chemical fertilizer and N₂O emission got to the most significant (P<0.01) in the two plots, and after using chemical fertilizer, the N₂O output increase 4.4 times for purple soil and 5.8 times for yellow soil;(5) Planting lettuce can make N₂O emission increase about 7.78 times, maize can increase 47% of the N₂O emission and cabbage can decrease about 30% of the N₂O;(6) Principal components and pathing analysis can point out that the soil temperature in 5cm and soil water content are two most important factors which have a significant effect on the N₂O production and emission from farmland, the temperature directly affects the rate of nitration and denitration reaction, and the soil water content can change the substrate concentration, the content of O₂ and the microorganisms activity et al. in the process of nitration and denitration; besides, the soil machinery composition, pH, organic matters content, the content of NO₃-N et al. also have compositive action on the N₂O output together with temperature and soil water content;(7) In the area of purple soil, N₂O emission and CO₂ emission has a significant linear relationship(P<0.01), and logarithmic relationship for yellow soil except for bare soil, and the significant level is P<0.05 for the treatment of plant and no fertilizer and P<0.01 for the treatment of plant +chemical fertilizer (PCF) and plant +chemical fertilizer+manure (PCFM) ;(8) The gross estimation on the routine farming soil for two experimental plots separately are 15.13 kg N hm^-2.a^-1 for purple soil and 27.49 kg N hm^-2.a^-1 for yellow soil;...