Persistence and establishment of red clover plants in extensive managed grassland in Norway

摘要

Red clover (Trifolium pratense L.) is normally a short-lived perennial and the number of plants in the field declines rapidly. In organic farming, the amount of clover in the field is decisive for the N_2 fixation and yield, and the protein content and quality of the forage produced. In Nordland County (66.27°N), there is a farm with some red clover plants in a > 15-year-old grassland sward. In the presented study, we examined the grassland botanical composition and attempted to determine the age ofred clover plants. Our hypotheses were that (1) extensive grassland management promotes self-seeding of red clover, which in turn, (2) would maintain a desired content of red clover over time. In addition, we tested two harvesting regimes of the first cut for seed maturation and seed quality at two locations in Norway. Red clover plants in old swards showed very high age and a branched root system. Very few seedlings were found in old swards, suggesting that self-seeding was insignificant. Experimentswith leaving the grassland after the first cut for seed production of clover failed due to poor seed maturation. Surface seeding of red clover in pure-grass plots gave good results, especially with early spring seeding.