[Effects of Long-term Organic Amendments on Soil N O Emissions from Winter Wheat-maize Cropping Systems in the Guanzhong Plain].

The primary aim of this study was to quantify the effects of long-term organic amendments on soil nitrous oxide (NO) emissions. Using static chamber-gas chromatograph technique, we measured NO fluxes from winter wheat-maize rotation system and related environmental factors in the Guanzhong Plain for one year (October 2014 to October 2015). Field experiments were based on the "Chinese National Loess Fertility and Fertilizer Effects Long-term Monitoring Experiment". Four treatments were control (CK, 0 kg·hm), NPK (NPK, 353 kg·hm), NPK combined with maize straw[NPKS, (353+40) kg·hm] and cattle waste[NPKM, (238+115) kg·hm]. During the experimental period, NO fluxes from CK treatment were small[<2.9 g·(hm·d)]; while emissions from fertilized treatments peaked after fertilization[up to 113.4 g·(hm·d) for NPKS] and irrigation[up to 495.0 g·(hm·d) for NPKM] during winter wheat and maize seasons, respectively. NO flux was significantly correlated to soil water-filled pore space for all treatments (>0.28,<0.05). Annual NO emissions were (0.1±0.0), (2.6±0.1), (3.4±0.7) and (2.9±0.3) kg·hm for CK, NPK, NPKS and NPKM, respectively. The fertilized treatments released higher NO emissions than CK treatment (<0.05), indicating that fertilization stimulated NO emissions. However, the differences in NO emissions were not significant among the fertilized treatments (=0.06), suggesting that organic amendments did not increase NO emissions obviously. The direct emission factors were 0.72%, 0.83% and 0.80% for NPK, NPKS and NPKM, respectively, all of which were lower than the IPCC default of 1%. The yield-scaled NO emission for NPKM was the lowest among the fertilized treatments.