Article

Nutrient Cycling in Agroecosystems

, Volume 63, Issue 2, pp 239-247

First online:

Nitrous oxide emissions for 6 years from a gray lowland soil cultivated with onions in Hokkaido, Japan

  • Kanako KusaAffiliated withLaboratory of Soil Science, Graduate School of Agriculture, Hokkaido UniversityNational Agricultural Research Center for Kyushu Okinawa Region
  • , Takuji SawamotoAffiliated withLaboratory of Soil Science, Graduate School of Agriculture, Hokkaido UniversityNational Institute for Agro-environmental Sciences
  • , Ryusuke HatanoAffiliated withLaboratory of Soil Science, Graduate School of Agriculture, Hokkaido UniversityField Science Center for Northern Biosphere, Hokkaido University

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Abstract

We studied nitrous oxide (N2O) emissions every growing season (April to October) for 6 years (1995∼2000), in a Gray Lowland soil cultivated with onions in central Hokkaido, Japan. Emission of N2O from the onion field ranged from 0.00 to 1.86 mgN m−2 h−1. The seasonal pattern of N2O emission was the same for 6 years. The largest N2O emissions appeared near harvesting in August to October, and not, as might be expected, just after fertilization in May. The seasonal patterns of soil nitrate (NO3 ) and, ammonium (NH4 +) levels and the ratio of N2O to NO emission indicated that the main process of N2O production after fertilization was nitrification, and the main process of N2O production around harvest time was denitrification. N2O emission was strongly influenced by the drying–wetting process of the soil, as well as by the high soil water content. The annual N2O emission during the growing season ranged from 3.5 to 15.6 kgN ha−1. The annual nitrogen loss by N2O emission as a percentage of fertilizer-N ranged from 1.1 to 6.4%. About 70% of the annual N2O emission occurred near harvesting in August to October, and less than 20% occurred just after fertilization in May to July. High N2O fluxes around the harvesting stage and a high proportion of N2O emission to total fertilizer-N appeared to be probably a characteristic of the study area located in central Hokkaido, Japan.

denitrification gray lowland soil nitrification nitrous oxide (N2O) rainfall