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This study aimed to evaluate the effects of a water limitation in different ecotypes and one variety of Lotus corniculatus L. on the production of secondary metabolites and their antioxidant activity in response to a water deficit (WD) through other seasonal times. A randomized block experimental design with three replicates was used. Two levels of soil water content and five genotypes were arranged in a factorial way (2 × 5) with ten treatments for replication. The 255301 ecotype showed significantly higher (p ≤ 0.05) concentrations of total phenols, with a concentration of 86.6 mg Gallic Acid Equivalent (GAE)/gram of fresh weight (gFW); total flavonoids, with a concentration of 63.2 mg Quercetin Equivalent (QE)/gFW); total tannins (71.7 mg GAE/gFW); and radical scavenging activity, with an average of 200 mg Trolox Equivalent Antioxidant Capacity (TEAC)/gFW) in winter under a WD. The 255305 ecotype showed an increase in radical scavenging activity of 230 mg (TEAC)/gFW) and a total tannin concentration of 65.3 mg GAE/gFW in winter and spring, respectively, under a WD. The 255301 ecotype showed an increase in the concentration of total saponins (254.8 mg saponins/gFW) in summer under a WD. All these responses were triggered to mitigate a water deficit and extreme temperatures.

This study aimed to evaluate different L. corniculatus L. ecotypes under water-deficit conditions to identify changes in relative water content and photosynthetic pigments as indicators of physiological responses during different years’ seasons. The experiment was conducted in a randomized block design with three replicates. Ten treatments were performed as a factorial of 2 × 5, where the first variation factor was the soil water content—no water deficit (NDW) with 100% field capacity (FC), and water deficit (DW) corresponding to 85.4% of the FC—and the second variation factor comprised four ecotypes and one variety of L. corniculatus. A significant effect was identified on the concentration of photosynthetic pigments, mainly total chlorophyll, with chlorophyll a in the 255301 ecotype with records of 187.8, 167.5, and 194.6 mg g−1 FW in WD, corresponding to an increase of 86.0%, 172.6%, and 16.6%, respectively, in relation the lower values obtained in the ecotype 202700 under NWD. In carotenoids, higher concentrations were observed in the 255301 and 202700 ecotypes and the Estanzuela Ganador variety under WD in most seasonal periods, except summer; a similar response was found in the 202700 ecotype and the Estanzuela Ganador variety during the winter season, also in WD. The results showed that the first two principal components accounted for 71.8% of the total variation, with PC1 representing chlorophyll a, chlorophyll b, and total chlorophyll, and PC2 representing carotenoids, temperature, relative chlorophyll index, and relative water content. The observations were grouped based on soil moisture content, with the optimal moisture group exhibiting higher chlorophyll and carotenoid concentrations. The findings suggest that soil moisture content significantly affects the performance of L. corniculatus ecotypes, and the plant shows seasonal variations in response to water-deficit conditions. This research contributes to understanding the physiological responses of L. corniculatus and its potential as a water-efficient forage crop for promoting sustainable agriculture and enhancing food security.