The effect of applying liquid organic fertilizer on the yield, quality, and soil fertility of Red Fuji apples

To address the current issue of imbalanced fertilization practices in Zhaotong apple orchards and to develop an effective fertilization strategy for improving the quality and productivity of ‘Red Fuji’ apples in the region, this study investigated the effects of integrated water and fertilizer management in high-density, dwarf ‘Red Fuji’ apple orchards. Specifically, we evaluated the impacts of different fertilization treatments on apple yield, fruit quality, and soil fertility. Six treatments were implemented, including three with increasing rates of liquid organic fertilizer and three combining liquid organic fertilizer with reduced chemical fertilizer rates, with conventional fertilization serving as the control. The results showed that, compared with conventional fertilization, both the increased application of liquid organic fertilizer and the combined application with reduced chemical fertilizer significantly enhanced apple yield, with increases ranging from 4.90% to 26.84%. These treatments also significantly improved fruit quality by increasing the contents of soluble solids and soluble sugars, as well as fruit firmness and coloration, while reducing fruit acidity. Moreover, all treatments significantly increased soil organic matter by 11.33% to 27.59%, and improved soil total nitrogen, available phosphorus, and available potassium levels. Among all treatments, the combined application of liquid organic fertilizer with a 20% reduction in chemical fertilizer (T6) produced the most favorable outcomes across all measured indicators.