| The apple orchards in the Weibei dryland plateau of the Loess Plateau face challenges such as low soil fertility and poor moisture retention. This study investigates the effects of different organic fertilizer application methods on soil moisture, nitrate nitrogen content, and apple yield and quality to provide technical support for the efficient and stable development of the apple industry in this region. Eight-year-old ‘Yanfu 10’ apple trees were used as experimental materials, with five treatments: (1) commercial organic fertilizer alone (OF), (2) commercial organic fertilizer combined with a microbial agent (OFM), (3) commercial organic fertilizer combined with a photosynthetic bacterial agent (OFP), and (4) commercial organic fertilizer combined with both microbial and photosynthetic bacterial agents (OFMP). A control treatment (CK) without organic fertilizer application was also included. The effects of these treatments on soil moisture content, soil nitrate nitrogen, shoot growth, apple yield, and fruit quality were examined.The results showed that all organic fertilizer treatments improved soil moisture content, nitrate nitrogen levels, new shoot length, fruit firmness, soluble solids, solid-acid ratio, and yield compared to the control. Among the treatments, OFMP and OFM had the most pronounced effects. Additionally, the chlorophyll content in the leaves of trees under the OFMP treatment was significantly higher than that under the OFM treatment, while the OFP treatment also led to a significantly higher chlorophyll content than OF treatment. This indicated that the addition of photosynthetic bacterial agents could significantly enhance chlorophyll content under the same fertilization conditions. However, there was no significant difference in fruit titratable acid content among treatments compared to the control. The OFMP treatment achieved the highest economic benefit, with a benefit-to-cost ratio of 2.06. Overall, the combined application of commercial organic fertilizers with microbial and photosynthetic bacterial agents improves soil moisture and nitrate nitrogen content, enhances fruit quality, increases yield, and provides the greatest overall benefits compared to other treatments. |
