Salt Effects on Alfalfa Seedling Emergence 1

Alfalfa ( Medicago sativa L.) is regarded as susceptible to salts at establishment. This study was conducted to evaluate: (i) emergence reduction by irrigation with saline waters; and (ii) the relationship among seed germination, hypocotyl salt injuries, and seedling emergence. Greenhouse experiments were conducted using ‘Moapa’ and ‘Mesilla’ grown in Bluepoint fine loamy sand (calcareous, thermic Typic Torripsamment). In Exp. 1, seedling emergence and salt accumulation near the soil surface were monitored after seeding at three depths (3, 10, and 15 mm) and irrigated with water of 0.8 to 7.6 dS m −1 . In Exp. 2, seed germination was measured in sponges moistened with saline solutions (0.8‐32 dS m −1 ). In Exp. 3, seedling emergence was monitored after placing a 5‐mm layer of salted‐sand having the saturation extract salinity of 0.8 to 45 dS m −1 onto emerging seedlings to evaluate hypocotyl salt injuries. Results indicated that the rate and final emergence of both cultivars declined when salinity of irrigation waters exceeded 4.3 dS m −1 , even though the seed germinated well in saline solutions of 28 dS m −1 . Soluble salts had accumulated mostly in the top 5‐mm depth where salinity increased to 20 dS m −1 in 4 days when irrigated at 4.3 dS m −1 . A significant reduction in emergence occurred in Exp. 3 when the salinity of the surface‐placed sand exceeded 17 dS m −1 . Emergence reduction observed from a seeding depth of 3 mm was probably due to the reduction in seed germination, whereas from seeding depths of 10 mm or more, emergence appeared to be limited by hypocotyl salt injuries after germination. Alfalfa could be established with minimal salt damage from water, up to approximately 4 dS m −1 , when seeded approximately 10 mm deep.