Soil N₂O Flux And Its Effective Factors In The Typical Farmland In The North China Plain

Soil N₂O flux of farmland soil in North China plain was measured by static chamber/GC at Yucheng comprehensive experimental station of the Chinese Academy of Sciences from Oct, 2004 to Oct., 2005. Daily and seasonal variations of soil N₂O fluxes and relationship of soil temperature, moisture, available nitrogen content and N₂O flux were analyzed under three kind of farming systems for winter wheat-summer maize, winter wheat-summer soybean and fallow-cotton rotation systems. Compositive effects of these four factors to soil N₂O flux were studied as well. The results indicated that:During growing season, the average emission fluxes of N₂O were 80.5 μg·m^-2·h^-1 , 90.5μg·m^-2· h^-1 , 20.7μg·m^-2·h^-1 and 54.6μg·m^-2·h^-1 respectively for winter wheat, summer maize, soybean and. cotton Annual gross emission fluxes were 6.9 kg·hm^-2, 4.7 kg·hm^-2 and 2.8 kg·hm^-2 respectively for winter wheat-summer maize, winter wheat-summer soybean and fallow-cotton rotation systems. Soil N₂O fluxes in winter wheat, summer maize and cotton farmlands presented obvious seasonal changing, which were lower in winter and higher in summer. Fertilization had distinct effect on it.Two forms of daily change orderliness and randomicity were showed in these four crop fields. Soil N₂O flux increased exponentially with soil temperature in winter wheat-summer maize rotation system, with seasonal Q₁₀ equal to 2.2 and daily Q₁₀ between 3.8⁴.5; Moreover, soil N₂O flux and NH₄⁺-N content showed significant linear relationship in winter wheat-summer maize and vacant-cotton rotation systems.The compositive effects of temperature, soil moisture, NO₃^--N and NH₄⁺-N contents on soil N₂O fluxes reached to extraordinary visible level in growing season for winter wheat-summer maize rotation system and soil moisture and NH₄⁺-N content were dominant factors. There were significant linear relationships between soil N₂O and CO₂ flux in four crop fields.