Establishment and persistence of legumes at sites varying in aspect, landscape position, and soil type

Pastures in Iowa are dominated by cool-season grasses, and vary greatly in landscape positions, slopes, and soils. This variation, along with seasonal climatic changes, can cause areas in pastures to vary greatly in forage production. Interseeding a mixture of legumes may help to extend edaphic and climatic plasticity to pasture systems to improve season-long dry matter production. To test this concept, a complex mixture of eleven legumes was frost interseeded into grass pastures containing different landscape positions, slopes, and soils, and was subjected to three different grazing schemes. Sideslope landscape positions had a greater legume composition as a percentage of total dry matter and total tiller number of pasture sites. Grazing also tended to either increase or maintain the legume percentage in the composition, while non-grazed pastures suffered legume composition decreases. Species richness also decreased as the grazing season progressed from spring to fall, and sideslope landscape positions tended to have greater numbers of legume species present than upland or bottomland landscape positions. Areas with the greatest species richness also had the greatest legume composition percentage. Landscape position can cause variation in dry matter production of legumes in pastures, and the legume species which contribute to the award also changes with the season and the landscape. Therefore, pasture improvements involving interseeding of legumes should entail site specific recommendations for optimal season-long forage production.