This experiment aimed to assess the impact of deficit irrigation on both the quantitative and qualitative yield of forage maize hybrids. The study was structured as a split-plot design, utilizing a randomized complete block design with three replications, at the Agricultural Research Station of Gorgan in the years 2021 and 2022. Deficit irrigation was implemented at four different levels as the main plots, which comprised 100%, 75%, 50%, and 25% of the water requirement. These main plots were further subdivided into subplots, consisting of four hybrid varieties, namely SC703, SC704, ZP548, and BK50. The results showed that the highest total biomass (47,939 kg ha−1) was obtained under 100% water requirement (control) and SC704 hybrid. The reduction in total biomass for the treatments at 75%, 50%, and 25% of the water requirement, when compared to the control treatment, amounted to 3160 kg ha−1 (7%), 21,354.5 kg ha−1 (47.4%), and 35,582.8 kg ha−1 (79.1%), respectively. Deficit irrigation significantly affected qualitative traits except for neutral detergent fiber (NDF) at the level of 1% and increased all quality traits. Accordingly, the highest percentage of crude protein (CP), NDF and acid detergent fiber (ADF) was obtained by hybrid SC703 with 50% water requirement (by 9.20%), hybrid BK50 under 25% water requirement (by 30.73%), and BK50 with 75% water requirement (by 44.03%). The highest water use efficiency (WUE) was observed in 75% of the water requirement (7.79 kg m−3). Considering the significant reduction in water consumption (1795 m3 ha−1) achieved with this treatment, it is advisable to recommend irrigation at 75% of the water requirement alongside the cultivation of the SC703 hybrid for forage production in the northern region of Iran.
