Impact of Deficit Irrigation on Forage Yield, Quality, and Drought Tolerance: A Comparative Study of Berseem and Persian Clover Genotypes in a Semi-Arid Region

Clover is recognized as one of the most distinguished forage crops within the leguminous family, particularly suited for temperate and humid regions. Given clover's sensitivity to drought stress, its yield and quality in semi-arid and arid regions heavily depend on the irrigation regimen. Revising irrigation and irrigation strategies due to global climate change is vital in semi-arid ecologies. To determine forage crops and varieties with high water use efficiency will have a key role in animal production in the future. The plants include Berseem clover and Persian clover species that can be grown in semi-arid ecologies. A two-year experiment was carried out in a semi-arid area (Karaj) of Iran, to investigate the impact of shortages of irrigation on production, forage values, efficiency of water use, and drought stress indices across five Berseem and five Persian clover genotypes. There were two levels of irrigation considered: full irrigation (100% moisture requirement) and deficit irrigation (50% water requirement). Among the genotypes studied, Berseem-Win exhibited the highest fresh forage yield (104.48 Mg ha–1) and dry matter yield (17.20 Mg ha–1), Berseem-Ekinaton displayed the greatest plant height (69.63 cm) and leaf area index (2.17), Berseem-Karaj recorded the highest energy content (2.76 Mcal kg–1) and digestible protein (13.69%), and Berseem-Alex showed superior energy efficiency in water use (4.88 Mcal m–3) and digestible protein production (0.246 kg m–3). The Berseem-Alex displayed the greatest drought tolerance. Persian clover genotypes exhibited lower drought tolerance compared to the Berseem genotypes, with the Harat emerging as the most tolerant among the Persian clovers. Overall, the findings suggest that Berseem clover genotypes possess greater potential for forage cultivation within semi-arid and arid areas than Persian clover.