Hard Seed and Field Establishment of Irrigated Alfalfa
- J. W. Hall ,
- D. G. Stout and
- B. M. Brooke
Alfalfa (Medicago saliva L.) seed lots contain a proportion of hard, water-impermeable seed that does not germinate readily during a 7- d germination test. Opinions differ as to whether or not hard seeds make a delayed contribution to an alfalfa stand. Scarification by five freeze-thaw cycles of 2 h at − 80 °C followed by at least 2 h at 20 °C can be used to make hard seeds permeable to water. A field experiment was carried out in 1990 and 1991 to determine the effects of hard-seededness and freeze-thaw scarification on the establishment and dry matter yield of irrigated alfalfa. Untreated (germination 50%) and scarified (germination 93%) seeds were sown at rates of 1, 5, and 10 kg ha−1 in two trials established 6 wk apart at different sites. Plant density increased 8-fold with the 10-fold increase in seeding rate but yield increased by only 42% in the first year and 13% in the second year. The results of the 7-d germination test suggested that scarification should have increased the plant density by 86%, but the observed increase was only 40%. Thus, either a fraction of the seeds made permeable by scarification did not produce plants or scarification injured some of the seeds that were already permeable. Owing to compensatory growth, yield was unaffected by scarification.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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