Effects of nitrogen split application on seasonal N 2 O emissions in southeast Norway
Nutrient Cycling in Agroecosystems(2019)
摘要
Nitrous oxide (N 2 O) emissions from cultivated soils correlate positively with the amount of N-fertilizer applied, but a large proportion of the annual N 2 O emission occurs outside the cropping season, potentially blurring this correlation. We measured the effect of split-N application (total N addition varying from 0 to 220 kg N ha −1 ) on N 2 O emissions in a spring wheat plot trial in SE Norway from the time of split-N application until harvest, and during the following winter and spring thaw period. N 2 O emissions were largest in the two highest N-levels, whereas yield-scaled emission (N 2 O intensity) was highest in the 0 N treatment. Nitrogen yield increased by 23% when adding 80 kg N ha −1 compared to adding 40 kg N ha −1 as split application, while corresponding N 2 O emissions were reduced by 16%. No differences in measured emissions between the N-fertilization levels were observed during the winter period or during spring thaw. Measurements of soil air composition below the snow pack revealed that N 2 O production continued throughout winter as the concentration in the soil air increased from 0.37 to 30.0 µL L −1 N 2 O over the 3 months period with continuous snow cover. However, only 7–28% of the N 2 O emitted during spring thaw could be ascribed to accumulated N 2 O, indicating de novo production of N 2 O in the thawing soil. The direct effect of split-N fertilizer rate on N 2 O emissions in sub-boreal cereal cropping was limited to the first 15–21 days after N-addition.
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关键词
Nitrous oxide, Split-N application rate, Yield-scaled emissions, Spring wheat, Off-season emissions
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