Study on the Nitrogen Response and Low Nitrogen Tolerance Variations in Different Tea Varieties

Selecting and breeding tea plant varieties with low nitrogen tolerance is crucial for reducing the application of nitrogen fertilizer in tea gardens and promoting the green and sustainable production of tea. Thus, a split-plot designed field experiment was conducted in a subtropical tea garden in China, where ten distinct cultivars were planted and exposed to two different levels of nitrogen (N) supply. This study aimed to assess the response of these cultivars to normal (450 kg ha⁻¹) and low (150 kg ha⁻¹) N fertilization treatments and to evaluate their tolerance to low N conditions. The results revealed notable differences in both the growth and biomass responses of the tea cultivars to N supply levels. Under low N supply, tea tree height, pruned litter biomass, and its nitrogen accumulation were all significantly lower than those under the normal N level. There was also a significant interaction effect between the cultivar and N level in the one-hundred-bud weight, new shoot yield, and its nitrogen content, respectively. The amount of total N uptake by harvested new shoots was relatively low, whereas a considerable amount of N was returned to the garden through pruned biomass. The aboveground biomass and its nitrogen accumulation could be considered as critical indicators for identifying nitrogen-tolerant cultivars with a variation coefficient by 20% and 20.57%, respectively. Additionally, cluster analysis showed that BY1 and LJ43 were strong low N-tolerant cultivars, while HJY was the most N-sensitive cultivar, closely followed by the ZN117 tea plants. In conclusion, significant disparities were observed in the adaptability of different tea cultivars to low N fertilization under the ambient field conditions. This study provided valuable theoretical insights and practical references for selecting N-tolerant tea varieties and reducing N fertilizer consumption in tea gardens.