<p>The purpose of this study was to assess glutamic acid’s potential effectiveness in compensating for irrigation water deficiency. To achieve the target above, two field experiments were conducted under sandy soil conditions during two winter seasons of 2019/2020 and 2020/2021 to investigate the role of glutamic acid with three concentrations (0, 5 and 10&#xa0;mg/l) on growth, yield, chemical composition and nutritional value of oat plants grown under three levels of irrigation water (100%, 75% and 50%). The findings clearly demonstrated how glutamic acid improved the quality and production of oat plants. Foliar application of oat fodder by glutamic acid with different concentrations (G₅ mg/l and G₁₀ mg/l) significantly increased their yield and yield attributes with superiority to 10&#xa0;mg/l treatment compared to control plants. In addition, foliar application of oat fodder with glutamic acid significantly improved the contents of DM %, CP %, CF %, EE %, NFE %, GE, (DE), ME. Nutritive values of oat plants were also improved. Also, DCP and TND improved. Cell wall composition was also improved. Moreover, glutamic acid treatments enhanced levels of photosynthetic pigments, carbohydrate constituents, IAA, and phenolic contents. On the other hand, decreasing irrigation water to 75 and 50% significantly decreased the previous characteristics. However, significant results were obtained for the interaction effect of glutamic acid and water deficit. From the obtained data it could be concluded that glutamic acid at G₅ mg/l or G₁₀ mg/l indicates satisfactory yield, quality plant productivity and good nutrition value under moderately limited irrigation water (75% water irrigation). Verifying these results will require additional research, investigating diverse application methods and concentrations.</p>