【Atmospheric Environment】Nonlinear response of nitric oxide emissions to a nitrogen application gradient: A case study during the wheat season in a Chinese rice-wheat rotation system

Miao Zhao^{a b} Yuhua Tian^a Min Zhang^a Yuanlin Yao^a Yuqin Ao^a Bin Yin^a Zhaoliang Zhu^a. Nonlinear response of nitric oxide emissions to a nitrogen application gradient: A case study during the wheat season in a Chinese rice-wheat rotation system. Atmospheric Environment 2014 doi:10.1016-j.atmosenv.2014.11.052

Abstract

The response of nitric oxide (NO) emissions to nitrogen (N) input in agricultural ecosystems is generally assumed to be linear but the availability of inorganic soil N exceeding crop N demands may cause a threshold response of NO. We conducted a four-rotation field measurement with discrepant N fertilizer rates during the wheat season of the rice-wheat rotation in the Taihu Lake region in China to test the hypothesis. Across all years a nonlinear model well characterized the response of cumulative NO emissions to N fertilizer rates. The direct emission factors of NO induced by fertilizer also increased nonlinearly with increasing N doses with a mean of 1.06% (ranging from 0.54% to 1.49%). NO emissions were low (<1.81 kg N ha^-1 yr^-1) over the 0-180 kg N ha^-1 fertilizer additions; above these additions the increasing N rates resulted in substantial NO increas