Fruit quality and yield of citrus orchards are co-regulated by complex interactions among soil properties, microbial communities, and plant physiological processes. However, systematic studies that integrate the soil–microbe–plant–fruit continuum remain limited. This study selected four representative ponkan orchards based on yield and fruit quality performance, and systematically determined and correlated key indicators in the soil–plant–fruit continuum. The results showed that the orchards with higher comprehensive performance exhibited more suitable soil pH, higher contents of soil organic matter and available nutrients, as well as higher activities of soil enzymes including urease and acid phosphatase. Compared with the orchards with lower comprehensive performance, soil bacterial and fungal Chao1, Shannon, and Simpson indices were higher in the orchards with higher comprehensive performance. Among the dominant phyla, the relative abundance of Proteobacteria was significantly higher, while that of Actinobacteria was significantly lower. Leaf photosynthetic indexes (chlorophyll content, net photosynthetic rate, Rubisco activity) of the higher-performing orchards were also significantly higher. Correlation analysis showed that soil microbial diversity and Proteobacteria were significantly positively correlated with soil nutrients, enzyme activities, leaf photosynthesis, fruit quality and yield, while Actinobacteria showed the opposite trend. These results provide a theoretical basis for soil management and high-quality cultivation of ponkan orchards.

The ponkan (Citrus reticulata Blanco cv. Ponkan), an important citrus crop, is increasingly threatened by soil acidification. This study evaluated the efficacy of various soil amendments, including lime alone (L), lime with gypsum and organic fertilizer (LGOF), lime plus K₂CO₃ (LK), and lime with chicken manure ash (LCMA), in mitigating soil acidification and improving ponkan seedling growth. Surface-applied lime raised topsoil pH and acid buffering capacity while reducing exchangeable Al. However, combined amendments (LGOF, LK, LCMA) more effectively alleviated acidity throughout the soil profile. They significantly increased pH and buffering capacity, decreased exchangeable H and Al in the 20–40 cm layer, and elevated exchangeable base cations (K⁺, Ca²⁺, Mg²⁺). These changes reduced Al content in roots, stems, and leaves, promoted deeper root growth, and increased biomass and nutrient uptake (N, P, K). Physiologically, combined amendments enhanced photosynthetic performance (chlorophyll, Pn, ΦPSII) and increased activity of key metabolic enzymes (Rubisco, SS, SPS, NR, GS), promoting sucrose, starch, and protein accumulation. LK rapidly raised subsoil pH and potassium levels, ideal for K-deficient orchards. LGOF and LCMA improved overall fertility by supplying Ca and Mg, with LGOF additionally enhancing soil structure in poorly structured acidic soils.