<p>Loading matrix of principal components.</p>

Five alfalfa varieties, namely Zhongcao No.13, WL440HQ, WL525HQ, WL903, and WL712, were subjected to a hydroponic cultivation experiment under controlled conditions of 25℃ room temperature, a nutrient solution concentration of 1.5 times the standard Hoagland formulation, and a 10-hour photoperiod. The plants were harvested every 30 days for six consecutive harvests, and the effects of harvest time on the yield and quality of different alfalfa varieties were observed. Principal component and membership function analyses revealed that the acid detergent fiber (ADF), neutral detergent fiber (NDF), relative feeding value (RFV), and yield of WL903 ranged from 22.77% to 25.75%, 28.31% to 32.42%, 197.46 to 233.84 (unitless), and 0.41 kg·m-2 to 0.59 kg·m-2, respectively. The membership function analysis of the five alfalfa varieties indicated that the ranking based on D-value was WL903 > WL440HQ > WL712 > WL525HQ > Zhongcao No.13. Compared with the other four varieties, this variety was superior in terms of yield and relative feeding value and could serve as a candidate for regional hydroponic alfalfa cultivation. However, it should be noted that this result is based on specific light and nutrient solution conditions, and further cost-effectiveness verification is needed for large-scale applications.