Optimizing fertilization under varying cultivation conditions: Insights from a meta-analysis on tea yield and quality

Fertilizer is widely used in the tea industry to enhance yield; however, a lack of a comprehensive understanding of fertilization efficiency often leads to overuse or misuse, resulting in soil acidification and a decline in soil biodiversity. This study investigates the impact of fertilizer management on tea yield and quality across different cultivation conditions primarily in China, providing critical insights for optimizing fertilization practices to promote sustainable production in the tea industry. By synthesizing 562 paired comparisons from 73 studies, we quantitatively evaluated how fertilization practices interact with environmental and cultivation factors, influencing tea production outcomes. We emphasized the importance of aligning fertilization practices with specific cultivation conditions. Random forest model analysis identified nitrogen application as a key factor in modulating tea-related indices. The fitted power function curve indicated a potential saturation effect in nitrogen uptake efficiency. A decline in the response ratios of both yield and phenol-to-ammonia ratio was observed in plots receiving nitrogen applications above 600 kg ha^-1·yr^-1, with values dropping to approximately 0.5 (absolute response ratio). This study highlights the non-synergistic relationship between yield and quality at varying levels of nitrogen application. While farmers seek to increase yield through fertilization, they may consider not only the cost of fertilizer but also the potential negative impact of improper fertilization on tea quality. A decline in quality could reduce product prices, ultimately affecting overall profit.