Status quo of nitrogen fertilizer application and loss in tea garden of China

Objectives Tea plant is a perennial leaf crop, and requires a large amount of nitrogen fertilizer for high yield and qulity of tea product, so excessive application of nitrogen fertilizer is common in tea production, which would possibly cause low nitrogen utilization efficiency and water and air pollution. This paper aims to investigate the nitrogen use amount in tea plantations, and sort out the main path of nitrogen loss, and propose available measurement for the control of the nitrogen loss.

Methods Nitrogen use, loss and tea garden were used as key words, we searched and screened the published literatures on CNKI and Web of Science. And then we summarized the tea yield, nitrogrn agronomic efficiency (NAE) and partial factor productivity of applied nitrogen (PFPN) under different application amounts of nitrogen fertilizers in tea garden, and compared their differences before and after 2000. The contribution of different N loss paths were calculated.

Results In the tea garden of China, the yield increase rate of N fertilization was averaged 41.7%, the NAE was 8.1 kg/kg, and the PFPN was 31.4 kg/kg. Both the NAE and PFPN before and after 2000 showed a downward trend. The N loss caused by ammonium and nitrate nitrogen leaching, ammonia volatilization and denitrification (N₂O emission) were 186.8, 48.8 and 16.7 kg/hm², and accounting for 33.9%, 15.1% and 3.6% of N application rate.

Conclusions Nitrogen use efficiency of tea garden in China is low, but its partial productivity is as high as 31.4 kg/kg, so nitrogen application is still necessary for high yield and efficient tea production, although the nitrogen use efficiency is going down after 2000. The loss of applied nitrogen is mainly caused by leaching of ammonium nitrogen and nitrate nitrogen and the volatilization of ammonia in tea garden. Therefore, optimization of nitrogen management is the key measurement to reduce nitrogen loss and improve nitrogen utilization rate.