Meta-analysis of the effects of chlorine fertilizer on yield increase and quality improvement of cash crops in China

Chlorine, an essential micronutrient, plays a crucial role in plant growth and development, significantly impacting the productivity and quality of various cash crops, including tobacco (Nicotiana tabacum L.), sugarcane (Saccharum officinarum L.), cotton (Gossypium hirsutum L.), and tamato (Solanum lycopersicum L). To quantitatively evaluate its agronomic effects, literature published between 2000 and 2021 was retrieved from CNKI, Wanfang, VIP, and the Web of Science databases using relevant keywords. A meta-analysis was performed to assess the impact of chlorine fertilization on yield enhancement and product quality in flue-cured tobacco, sugarcane, cotton, and tomato cultivation across China. Results showed that chlorine fertilization significantly increased the yields of flue-cured tobacco, sugarcane, and cotton. In flue-cured tobacco, chlorine administration increased reducing sugar content while markedly lowering nicotine concentration and the potassium-to-chlorine ratio. In cotton, chlorine application improved both fiber length and yield, leading to enhanced fiber quality. In contrast, tomato yields exhibited no significant response, although vitamin C content declined notably. The optimal chlorine application rates for flue-cured tobacco, sugarcane, cotton, and tomato were 30–40 kg chlorine/hm², <300 kg chlorine/hm², 80–110 kg chlorine/hm², and 0–100 kg chlorine/hm², respectively. Regional heterogeneity was evident, with cotton showing higher yield increases than flue-cured tobacco in both eastern and western China. Additionally, chlorine fertilization exerted stronger effects on cotton than on flue-cured tobacco or tomato across these regions. Overall, chlorine fertilization effectively enhances yield and certain quality traits of key crops in China, although its efficacy depends on crop type, dosage, timing, and geographic conditions. A systematic approach that integrates these factors is critical for optimizing chlorine fertilizer management to improve agricultural productivity and promote sustainable crop production.