Proper water and nitrogen management is critical for balancing vegetative-reproductive growth in apple trees, while mismanagement aggravates interannual fluctuations in fruit yield and quality. To elucidate the interactions among tree growth, yield, fruit quality, and resource use efficiency under different water and nitrogen levels, a five-year drip-fertigation experiment was conducted in 2017 on the Loess Plateau, China. Two irrigation levels (W1: 85% field capacity (FC); W2: 100% FC) and four nitrogen rates (0, 120, 240, and 360 kg ha-1, N1-N4) were tested. Results indicate that nitrogen application up to 240 kg N ha-1 (N3) extended active (Taas) and rapid growth periods (Delta t) of spring shoots, increasing their growth rates, maximum growth length, and leaf area index increment (LAII). Thereby enhancing fruit yield by 21.43%-45.05%, water productivity (WPc) by 16.87%42.62%, total soluble solids, soluble sugars, vitamin C content, sugar-acid ratio, and the sustainability and stability of fruit yield and quality. Partial least squares path modeling further demonstrated that spring shoot increment (SSI) exerted greater total effects than LAI on yield (0.929), fruit quality (0.586), and WPc and Agronomic nitrogen efficiency (AEN) (0.736). The AEN decreased with increasing nitrogen rates. Higher irrigation (W2) shortened Taas and Delta t, promoted spring shoot growth, yield, WPc, and yield sustainability and stability but reduced fruit quality and its sustainability and stability. Overall, W1N3 represents an optimal irrigation and nitrogen management strategy, enhancing orchard productivity, stabilizing fruit yield and quality, and supporting sustainable apple production on the Loess Plateau.