Aims and methods <p>Sustainable intensification of forage production in semiarid regions requires innovative agronomic strategies that optimize yield-quality-resource trade-offs. Addressing a critical knowledge gap, this study systematically evaluated the combined effects of three irrigation levels (I₁: 30–50%; I₂: 50–70%; I₃: 70–90% of field capacity) and three cutting frequencies (C₀: single harvest; C₁: one cut prior to final harvest; C₂: two cuts prior to final harvest) on forage sweet sorghum (<i>Sorghum bicolor</i> (L.) Moench) using an auto-weighted lysimeters experiment.</p> Results <p>Irrigation significantly boosted biomass, with I₂ and I₃ increasing dry matter yield by 39.6% and 103.2% over I₁. Mowing frequency notably affected forage quality; C₀ reduced the grading index of forage sorghum by 55.9% compared to C₂. However, repeated mowing reduced water use efficiency, as C₂ and C₁ lowered dry matter water use efficiency by 58.6% and 41.7% versus C₀. A significant irrigation-mowing interaction was found: the I₂C₀ regime enhanced resource use efficiency, increasing crude protein water use efficiency by 8.7% over I₂C₂. Crop nitrogen accumulation increased with irrigation amount, but mowing decreased partial factor productivity of applied nitrogen (PFP). I₂ raised PFP by 39.3% over I₁, and C₀ boosted PFP by 506.1% over C₂. Ultimately, I₂C₀ performed comparably to I₃C₀ while reducing total water consumption by 14.6%, and is therefore recommended for semiarid regions where water is scarce.</p> Conclusions <p>Optimal performance was achieved at 50–70% FC with a single harvest at maturity which enhanced both dry matter accumulation and forage nutrition while improving water-nitrogen use efficiency.</p>