Large loss of reactive nitrogen and the associated environmental damages from tea production in China

Tea (Camellia sinensis L.), the most popular beverage worldwide and an important cash crop in China, plays a crucial role in the socio-economic landscape. Reactive nitrogen (Nr) loss from tea cultivation in China has become a major environmental problem due to the high input of N fertilizers. However, the scale of the Nr loss and its environmental impact on tea production in China remains unknown. Hence, we conducted a comprehensive meta-analysis of ammonia volatilization (NH₃), nitrogen oxide (NO_x), nitrous oxide (N₂O) emissions, N leaching (total nitrogen, TN), and N runoff (TN) losses in tea plantations in China. The total Nr loss in Chinese tea plantations was 376 Gg yr⁻¹ (149 kg N ha⁻¹ yr⁻¹) in 2014, with N leaching, NH₃ volatilization, N₂O emissions, NO_x emissions, and N runoff losses accounting for 52.2 %, 33.2 %, 7.5 %, 5.4 %, and 1.7 %, respectively. The total Nr loss-related environmental damage cost of tea cultivation reached 9.53 billion CNY yr⁻¹ in 2014, which was 7.7 % of the total tea production output value. The bulk of the environmental damage cost was attributed to NH₃ volatilization (49.1 %), N₂O emissions (24.9 %), and N leaching (19.2 %). Large Nr losses occurred during tea production in Sichuan, Hubei, Guizhou, Yunnan, Zhejiang, and Hunan provinces, accounting for 17.7 %, 17.0 %, 13.4 %, 10.7 %, 7.6 %, and 7.0 % of the total Nr losses in China, respectively. Our analysis showed that the adoption of integrated nutrient management reduced N fertilizer inputs to 300 kg N ha⁻¹, lowered Nr loss from 376 Gg to 172 Gg yr⁻¹, and reduced the environmental damage cost of N loss by 45.4 %. These findings, along with detailed data on the N balance of tea cultivation, provides critical information needed to develop effective region-specific N nutrient management practices and policies for sustainable and profitable tea crop production in China, and possibly in other similar geographies.