Optimized fruit load and fertilization management for improving pomelo productivity with lower environmental costs

Agriculture green development necessitates a synergistic approach to address multiple objectives, such as yield, quality, production efficiency, and environmental sustainability. The lack of a multi-objective comprehensive evaluation method based on a holistic perspective is a challenge that limits its progress and further development. Citrus, including pomelo (C. grandis (L.) Osbeck), is the world's largest fruits, and its green production is directly related to achieving multiple goals such as economic benefits and human health. Fruit load and fertilization management are critical agronomic practices in pomelo production; however, their combined effects are not yet fully understood. A two-year field experiment was conducted, involving three fruit load levels (low-, medium-, and high-fruit load as 40 ± 5, 65 ± 5, and 90 ± 5 fruits plant−1) and two fertilization strategies (farmer’s fertilization with 1000 N-900 P2O5-900 K2O kg ha−1 and optimized fertilization with 250 N-100 P2O5-200 K2O kg ha−1 and 2000 kg ha−1 organic fertilizer) to investigate the effects on fruit yield, quality, fertilizer partial factor productivity (PFP), economic benefits, greenhouse gas (GHG) emissions, and carbon footprint, as well as three comprehensive evaluate methods of the Grey Relational Analysis (GRA), the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS), and the Combined Evaluation Method (CEM) were employed. Compared to low-fruit load, high-fruit load significantly increased fruit yield but adversely affected quality by reducing single fruit weight, color, sugar content, and antioxidant capacity. In contrast, medium-fruit load offered a balanced trade-off by sacrificing a modest amount of yield to enhance fruit quality, and yield losses were offset by an increased proportion of high-quality fruit, thereby elevating overall income. Moreover, optimized fertilization significantly reduced chemical fertilizer inputs without compromising yield or quality, while substantially increasing PFP and reducing GHG emissions. However, the comprehensive evaluation revealed that the combination of medium-fruit load with optimized fertilization provided the best overall performance, achieving the highest scores across GRA, TOPSIS, and CEM methods. Our study provides a strategy of optimized fruit load and fertilization management that can synergistically improve fruit productivity and environmental sustainability for pomelo green development. It is recommended that a comprehensive evaluation method based on quantitative multi-objective indicators be implemented and developed.