Emergence and survival of legumes seeded into pastures varying in landscape position

Landscape position affects legume establishment in pastures. We conducted this study to (i) determine the role of emergence and survival on establishment of legumes on summit and backslope positions and (ii) examine how competition, as influenced by sward-cutting height and N fertilization, affects legume emergence and survival across these positions. We no-till drilled a mixture composed of red clover (Trifolium pratense L.), alfalfa (Medicago sativa L.), and birds-foot trefoil (Lotus corniculatus L.) into an existing cool-season grass pasture at Rhodes, IA, in 1998 and 1999. Treatments consisted of landscape positions (summit and backslope), N fertilizer rates (0, 22, 44, and 89 kg [ha.sup.-1]), and sward heights (uncut, 5, and 13 cm). Landscape position did not affect legume emergence in swards cut at 5 and 13 cm. At those heights, emergence averaged 1041 and 831 seedlings [m.sup.-2]. In swards cut at 5 cm, 62 plants [m.sup.-2] survived on summits vs. 183 plants [m.sup.-2] on backslopes. Legume emergence and survival generally decreased as sward height and N fertilization increased but interactions with landscape position occurred. Addition of 89 kg [ha.sup.-1] N was required to reduce survival on backslopes to 39 plants [m.sup.-2], a density similar to that on summits. Our results show that seedling survival limits legume establishment on summit positions in pastures. Legume establishment is successful on backslopes because of less competition from grass. We recommend that legumes be seeded on backslope positions in pastures, N fertilizer not be applied, and grass competition be reduced before seeding legumes in pastures.
LEGUMES improve the production and nutritional value of forage in cool-season grass pastures. Pastures composed of grasses and legumes produce more dry matter than grass-only pastures (Taylor and Allinson, 1983). [...]