SEEDLING EMERGENCE AND SURVIVAL OF ANNUAL PASTURE LEGUMES IN NORTHERNNEW-SOUTH-WALES

Seedling emergence and survival of 15 annual pasture legumes was studi ed in the field at Tamworth, northern New South Wales. Emergence was m easured in permanent quadrats (0.09 m(2)) in covered and uncovered are as approximately every 15 days from 30 November 1983 to 30 November 19 84. Survival of seedlings was estimated from 15 December 1983 to 31 Au gust 1984, before plants senesced. Emergence was generally highest in summer and autumn following seed set and lowest in winter and spring. Two legumes, Medicago scutellata cv. Sava and Trifolium subterraneum u m cv. Seaton Park, had high emergence in winter (mid July). Total seed ling emergence was highest (P < 0.05) in covered areas of cv. Seaton P ark and uncovered areas of T. hirtum cv. Hykon. All T. subterraneum cu ltivars, M. minima, Astragalus hamosus cv. Ioman, Vicia villosa cv. Na moi, and M. truncatula cv. Paraggio had higher total emergence in cove red compared with uncovered areas. In contrast, total emergence of M. aculeata, M. truncatula cv. Jemalong, Sava, and Hykon was lowest in co vered areas. Cover had little effect on the total emergence of M. trun catula cv. Sephi and T. glomeratum. Of the 7700 individual seedlings m arked from November 1983 to August 1984. a mean of only 31% (covered) and 41% (uncovered) survived until 31 August 1984. For each emergence time, highest (P < 0.05) survival rate coincided with the highest (P < 0.05) number of emerged seedlings in 4 of the legumes in covered area s (cv. Namoi, 31 January; cv. Ioman, 31 March; cv. Hykon, 15 April; cv . Sava, 15 July; Table 4) and 9 in uncovered areas (cvv. Nungarin, Sea ton Park, and Namoi, 31 January; M. aculeata and cv. Sephi, 28 Februar y; cvv. Jemalong and Ioman, 31 March, T. glomeratum, 15 April; cv. Sav a, 15 July). In all other legumes there was no optimum time for emerge nce, since the highest (P < 0.05) survival rates were associated with seedling survivals <50%. Generally, survival curves with a mortality c onstant rather than a mortality rate were a better fit (P < 0.05) for most legumes and times. This implied that these survival curves were d etermined at the time of recruitment, and declined at a constant rate, despite below-average post-emergence rainfall in May-June. Low rates of survival at times of highest (P < 0.05) emergence indicated that th ere may have been some density-dependent regulation in some of the leg umes.