| 其他摘要 | The global warming potential of nitrous oxide (N2O) is 298 times that of carbon dioxide (CO2), and N2O degrades
stratospheric ozone. Agriculture N2O emission accounts for 59% of anthropogenic N2O emission. Microbial nitrification and
denitrification are the major pathways of N2O production in soils. Synthetic fertilizers application in China is still the main way
in agricultural production, so the increase of N2O emissions might be inevitable. The annual synthetic nitrogen (N) fertilizer
consumption in China increased from 9.34×106 t in 1980 to 22.97×106 t in 2009, and it accounted for more than one fifth of the
total world consumption in 2007. The harvest area of vegetable crops rose from 9.5×106 hm2 in 1995 to 18.4×106 hm2 in 2010
in China and is still increasing. The fertilization rate for vegetable crops in China was 628.05 kg/hm2, nearly 2 times that for
cereal crops (314.4 kg/hm2) in 2006, of which N fertilizer occupied the largest share. The rough estimation showed that N2O
emissions from vegetable fields accounted for 20% of the total direct N2O emission and N emission accounted for 17% of total
N consumption nationally. Besides, agricultural practices such as irrigation and aeration potentially affect N2O emission from
soils through influencing soil physical and chemical characteristics to constrain soil microbial processes. However, the
microbial pathways of N2O production after N application and irrigation input in aerated condition are not well known. In
order to reveal the effects of water and nitrogen coupling on soil N2O emission characteristics under aerated irrigation, and
further put forward effective reduction measures, a field experiment with celery was conducted in greenhouse in Yangling
District of Shaanxi Province. The experiment adopted 2 irrigation levels (I1: full irrigation, 1.0 Ep; I2: deficit irrigation, 0.75
Ep. Ep is the cumulative evaporation from a 20 cm diameter pan between 2 irrigations) and 4 N levels (N0: 0 kg/hm2; N150:
150 kg/hm2; N200: 200 kg/hm2; N250: 250 kg/hm2), and 8 treatments in total. In the present study, the effects of irrigation
levels, nitrogen application amount, soil temperature and moisture, quantities of nitrifying bacteria and denitrifying bacteria on
soil N2O emission were also analyzed. The results showed that the N2O emission from the full irrigation treatment was
significantly higher than the deficit irrigation treatment. Nitrogen increased the cumulative N2O emission significantly under
the same irrigation level. The cumulative N2O emissions of N150, N200 and N250 treatments were 2.30, 4.14 and 7.15 times
that of N0 treatment in the whole growing season of celery, respectively. The correlation analysis showed that the significant
exponential relationships existed between soil N2O emission and soil temperature, water filled pore space (WFPS%), and
nitrate content. And the significant positive relationship was observed between soil N2O emission and nitrifier and denitrifier.
There was no relationship between soil N2O emission and soil ammonium content. Irrigation and fertilization were contributed
to the improvement of crop yield, but the soil N2O emission was also significantly increased. Therefore, the combination of N
application amount of 150 kg/hm2 and deficit irrigation was the best coupled mode of water and nitrogen to increase celery
yield and reduce N2O emission among the 4 treatments. It should be heavily emphasized in future in the Northwest China. The
results can provide valuable information for the selection of water-saving and nitrogen-saving method in Northwestern region. |
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