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Abstract
‘Grasslands Nui’ perennial ryegrass (Lolium perenne L.), ‘Grasslands Wana’ cocksfoot (Dactylis glomerata L.), and ‘Grasslands Huia’ white clover (Trifolium repens L.) were surface-sown in spring into pre-treated hill country swards. Appearance, survival, and morphological development of seedlings were measured. Final seedling appearance of the grasses was similar (33% of seed sown) although ryegrass seedling appearance was more rapid than cocksfoot for the first 24 days after sowing. White clover seedling appearance was 58%. Survival of seedlings in plots laxly grazed before sowing was generally poorer than in hard-grazed or herbicide-treated plots. Species differed in seedling survival in the order: ryegrass= cocksfoot = white clover. Mean establishment levels 145 days after sowing were 30% for white clover, 23% for cocksfoot, and 25% for ryegrass. Herbicide treatment substantially improved seedling development for all 3 species. Analysis of the fate of grass seed showed losses were greatest immediately after sowing, with 62% of ryegrass seed and 57% of cocksfoot seed failing to emerge as seedlings. The causes of non-appearance must be determined if grass over-sowing is to become a more reliable operation. White clover losses were more equally distributed between pre- and post-appearance phases. Most seedling losses were caused by environmeptal stresses or pest damage. Herbicide use was not essential for establishment of white clover and ryegrass but was necessary for slower-germinating cocksfoot. However, chemical reduction of competition from resident vegetation accelerated the establishment of all 3 species. It is concluded that much more information is required before the role and economics of species introduction from oversowing in hill country can be assessed.
