As nitrogen (N) fertilizer applications and N deposition have increased worldwide, global levels of nitrous oxide (N₂O) have increased, resulting in changes in the N cycle. Elevated applications of synthetic N fertilizers, coupled with land use and climate changes, are the main factors that control N₂O emissions from tropical soils. However, few studies have examined changes in soil N₂O emissions in response to the ongoing deposition of different forms of N in tropical forests in China.

Prof. ZHNAG Yiping and his team of Xishuangbanna Tropical Botanical Garden (XTBG) conducted a study at a managed rubber plantation in Xishuangbanna to see how soil N₂O emissions were influenced by nitrogen fertilizers in tropical rubber plantations. They measured N₂O fluxes from fertilized and unfertilized rubber plantations at Xishuangbanna in southwest China over a two-year period. They quantified the influence of synthetic N fertilizers on N₂O emissions and assessed spatial and temporal variations in N₂O fluxes. They then identified the time and extent of the effect of mineral N fertilizer applications on N₂O fluxes, and identified the environmental factors that controlled N₂O fluxes in tropical rubber plantations.

They found that the N₂O flux was higher from the fertilized rubber plantation than from the unfertilized rubber plantation. The increased fertilizer ratio of the rubber plantation was less than the ratios reported for subtropical forests in southeast China. There were significant correlations among soil temperature, soil water content, and N₂O flux rates for the different treatments. NH₄⁺-N and N₂O emissions were significantly and positively correlated, which predicted that nitrification may be the main N₂O emission way in the rubber plantation.

The N₂O emission ratios for N-fertilized rubber plantations were higher than for other plantation types, which may have significant implications for the local global warming potential. If tropical rainforests were converted to fertilized rubber plantations, regional N₂O emissions may enhance local climate warming.

The study entitled “The effects of nitrogen fertilization on N2O emissions from a rubber plantation” has been published in Scientific Reports.