This study aims to verify the ancient wisdom of "fallen leaves returning to their roots" and its application potential in semiarid regions. Two-year (2024-2025) field observations on tail vegetable retuning to soil depth (0-20 cm and 20-40 cm) were conducted in a semiarid cauliflower field. The data showed that there existed a distinct, slowly-releasing trend of water and nutrients during the decomposition of the tail vegetable. Soil water availability significantly increased by 24.5-28.2%, relative to no-returning (CK, p < 0.05), and continuously rose with increasing returning amount, soil depth, and duration (p < 0.05). Such a tendency became more pronounced when applied with chemical fertilizer, showing an unexpected priming effect. Also, the nutrients of the tail vegetable were also gradually released, when soil N-P-K were progressively improved. Accordingly, enhanced water and nutrient uptake by cauliflower was observed, resulting in higher photosynthetic rates, biomass, and curd production. Here, chemical fertilization was reduced by > 30% without yield loss. Soil enzyme activities, including urease, catalase, and alkaline phosphatase, were significantly increased during microbial-driven mineralization (p < 0.05), thereby promoting the release of NPK. Herein, soil organic C and N levels, microbial biomass, and nutrient buffering capacity were evidently strengthened. Additionally, plastic film mulching substantially intensified the above-mentioned trends via improving soil hydrothermal status for accelerating mineralization, justifying the above findings. We first confirmed the above ancient wisdom, and highlighted that the tail vegetable in topsoil acted as a slowly-released water and fertilizer to ensure field productivity and soil health with less chemical input.