Effect of different irrigation regimes on the production of forage, protein, energy, and water use efficiency in the Berseem clover cultivars

To evaluate the quantitative and qualitative forage yield of clover cultivars under water deficit, a split plots experiment was conducted in randomized complete block design with three replications at the Seed and Plant Improvement Institute, Karaj, Iran, for two cropping years (2017-18 and 2018-19). Three irrigation regimes included full irrigation (supplying 100% of clover water requirement), moderate stress (supplying 75% of clover water supply) and severe stress (supplying 50% of clover water supply) as the main factor, and five clover cultivars (Karaj, Elite, Ekinaton, Win and Alex) were evaluated as the sub-factor. The results showed that the maximum yield of fresh forage and dry matter in all three irrigation levels were obtained from Win and Karaj cultivars and the minimum from Ekinaton cultivar. The highest water use efficiency for the production of lactation energy at the irrigation levels of 100%, 75%, and 50% was obtained from Win, Alex and Elite cultivars, respectively. In water deficit stress, dry matter yield, metabolizable protein yield, content and yield of net lactation energy decreased, whereas metabolizable protein content increased. In addition, water deficit stress increased water use efficiency for the production of dry matter, metabolizable protein, and net lactation energy. Overall, due to the both quantitative and qualitative traits, Elite and Karaj cultivars are recommended as the best genotypes for cultivation under water deficit stress conditions.