In arid and semi-arid regions of China, effective irrigation management and agronomic strategies are essential for enhancing the soil water environment and optimizing water productivity. A three-year (2020–2022) field experiment was conducted in the Ningxia Water Saving Agriculture Science and Technology Park, a semi-arid region in northwest China, to assess the impact of planting patterns, watermelon irrigation quotas and their interaction on soil moisture status, yield and quality. The experiment encompassed: (1) two planting patterns: Apple-watermelon agroforestry and watermelon sole-cropping; and (2) three irrigation quotas (W1: 105 mm, W2: 210 mm, and W3: 315 mm). As the years progress, there is a decreasing trend in the average soil water content (SWC) of the 0–100 cm soil layer within the agroforestry system. During the flowering and fruit setting stage and expansion stage in 2022, the soil water content (SWC) in the agroforestry planting pattern is significantly lower than that in the watermelon sole-cropping pattern. Within the agroforestry planting pattern, the W1 and W2 irrigation quotas increase the average fruit weight, soluble solids content, and sugar content but reduce watermelon yield. The interaction between the W3 irrigation quota and agroforestry planting pattern promotes leaf photosynthesis, and extends the watermelon fruit expansion stage and maturity stage to compensate for the decrease in yield.

In summary, the agroforestry planting pattern improves the quality of watermelon fruit, increases soil water utilization, and reduces yield. For those seeking sustainable solutions to enhance land productivity and water use efficiency, apple-watermelon agroforestry emerges as a more promising alternative.