Forage-legumes are difficult to establish compared with many field crops. The small seed size of most forage-legumes necessitates seeding at shallow depths, where the seed is vulnerable to soil water deficits resulting from evaporation. Dehydration causes death once seeds germinate and radicle emergence occurs.
Adequate soil water and firm soil are prerequisites for successful germination of seed. Studies in the 1960's demonstrated that emergence of alfalfa seedlings improved as the planting depth and soil compaction increased from 0 to 1 inch (0 to 2.5 cm) in depth and 0 to 120 lb/2 (0 to 83 kPa) respectively, because soil water and seed-soil contact increased progressively at greater depths. These data suggest that no-till (NT) systems may offer advantages compared with conventional till-plant (CT) systems, since soil water is conserved and soil compaction increases when tillage is decreased.
Sweetclover, black medic, and alfalfa each were sown in NT and CT seedbeds to determine if eliminating tillage enhances forage legume establishment. Each legume species was planted on two different dates. On November 16, 2001, polymer coated seed of the three forage-legume species was planted. At the time this planting was completed both air and soil temperatures were about 40oF. The second date that dormant-seeding of legume species occurred was November 29, 2001. The soil temperature at the 4-inch depth under stubble was 31oF while the air temperature was 5oF at the time of planting. Uncoated seed was planted on this date. Seeding depth for both dates and for both conventional- and no-till plots was about ¾ of an inch.
The three legume species also will be planted in the spring. Seedlings will be counted to determine which treatment results in the highest percentage of seedlings being established.
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