Establishment of ryegrass, cocksfoot, and white clover by oversowing in hill country

Abstract

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.