The effects of nitrogen fertilization on N(2)O emissions from a rubber plantation

To gain the effects of N fertilizer applications on N(2)O emissions and local climate change in fertilized rubber (Hevea brasiliensis) plantations in the tropics, we measured N(2)O fluxes from fertilized (75 kg N ha(−1) yr(−1)) and unfertilized rubber plantations at Xishuangbanna in southwest China over a 2-year period. The N(2)O emissions from the fertilized and unfertilized plots were 4.0 and 2.5 kg N ha(−1) yr(−1), respectively, and the N(2)O emission factor was 1.96%. Soil moisture, soil temperature, and the area weighted mean ammoniacal nitrogen (NH(4)(+)-N) content controlled the variations in N(2)O flux from the fertilized and unfertilized rubber plantations. NH(4)(+)-N did not influence temporal changes in N(2)O emissions from the trench, slope, or terrace plots, but controlled spatial variations in N(2)O emissions among the treatments. On a unit area basis, the 100-year carbon dioxide equivalence of the fertilized rubber plantation N(2)O offsets 5.8% and 31.5% of carbon sink of the rubber plantation and local tropical rainforest, respectively. When entire land area in Xishuangbanna is considered, N(2)O emissions from fertilized rubber plantations offset 17.1% of the tropical rainforest’s carbon sink. The results show that if tropical rainforests are converted to fertilized rubber plantations, regional N(2)O emissions may enhance local climate warming.