Response of Soil Acidification, Fruit Yield, and Quality to Organic Fertilizer and Dolomite Powder Application in Pomelo Orchards

Soil acidification and base cation depletion constrain sustainable pomelo production in subtropical orchards. We hypothesized that the co-application of organic fertilizer and dolomite powder would alleviate soil acidification, improve Ca and Mg supply, and enhance pomelo yield and fruit quality more effectively than either amendment alone. A two-year field experiment was conducted in a pomelo orchard in southern Fujian Province, China. Four treatments were established: optimized fertilization alone (CK, 200 N-0 P2O5-200 K2O kg ha−1), optimized fertilization plus organic fertilizer (OF, 200 N-0 P2O5-200 K2O kg ha−1 + 7500 kg ha−1 organic fertilizer), optimized fertilization plus dolomite powder (DP, 200 N-0 P2O5-200 K2O kg ha−1 + 2145 kg ha−1 dolomite powder), and optimized fertilization plus organic fertilizer and dolomite powder (OF + DP, 200 N-0 P2O5-200 K2O kg ha−1 + 7500 kg ha−1 organic fertilizer + 2145 kg ha−1 dolomite powder). Pomelo yield, economic benefits, fruit quality, fruit mineral nutrients, and soil physicochemical properties were determined using standard procedures. Soil analysis showed that OF + DP most consistently increased soil pH and exchangeable Ca and Mg, while organic fertilizer improved soil organic matter. Compared with CK, OF + DP increased yield by 34.27% and 30.13% in 2023 and 2024, respectively, mainly by increasing fruit number per tree. OF + DP also produced the highest net profit, improved total soluble solids and TSS/TA, and increased fruit K, Ca, and Mg concentrations. These results indicate that combining organic fertilizer with dolomite powder is an effective amendment strategy for improving acidified pomelo orchard soils and productivity.