Irrigation technology, irrigation dose, and crop genetic impacts on alfalfa yield and quality

In water limited environments, alfalfa ( Medicago sativa) is often criticized for its high water use, prompting interest in optimizing irrigation technologies, deficit irrigation, and drought-tolerant genetics. However, potential cumulative benefits from combining water-saving strategies have not been previously identified. This study evaluated the independent and combined effects of five irrigation technologies (low-elevation Nelson advantage, low-elevation precision application, low-elevation spray application, mid-elevation spray application, and mobile drip irrigation), four irrigation doses (growers’ typical full dose, a 25 % reduction, and two 50 % reductions, uniform and growth stated-targeted), and two alfalfa varieties (growers’ conventional and drought-tolerant) across three Utah sites from 2020 to 2022. No interaction effects were found among these factors, indicating that stacking multiple water-saving strategies did not enhance yield or forage quality. Low-elevation sprinkler technologies generally outperformed mid-elevation and mobile drip irrigation, though results varied by environment. Deficit irrigation at 25 % reduction often maintained yields similar to growers’ Full irrigation dose, while 50 % reductions consistently decreased yield by 22–54 %. However, deficit irrigation improved forage quality and water use efficiency. Decision tree models revealed that maximizing relative feed value-adjusted water use efficiency primarily depended on matching irrigation dose and technology to site-specific climate demand rather than applying Full irrigation. These findings suggest that moderate deficit irrigation and low-elevation sprinkler technologies can improve forage quality and water resource efficiency without substantial yield loss that occurs with 50 % deficit irrigation. • No cumulative benefit from combining genetics, irrigation technology, deficits. • Low-elevation delivery systems improved yield but varied by environment. • 25 % deficit irrigation maintained yield; 50 % reductions consistently lowered yield. • Forage quality and water use efficiency increased under deficit irrigation.