Degree Type


Date of Award


Degree Name

Doctor of Philosophy



First Advisor

Kenneth J. Moore


Utilization of warm-season grass pastures in combination with cool-season pastures can enhance efficiency of forage growth for livestock production. By establishing legumes in warm-season grass pastures, forage quality can be improved. A complex mixture of legumes was interseeded into existing warm-season grass pastures in western Iowa. Forage quality values indicated that warm-season grass/legume pastures had potential to enhance livestock production; however, actual animal gains did not reflect this improvement. Observations were made of a high number of cool-season grass species present in pastures (39-78% of the total species composition). Due to an invasion of cool-season grass (smooth bromegrass, Bromus inermis) into warm-season grass pastures, pasture communities and qualities were not consistent over years. Despite encroachment of cool-season grass into warm-season grass pastures, warm-season grass pasture communities can be improved with legumes with proper management.;Spatial patterns of specific legume species were identified across landscape positions. Western Iowa pastures exhibit a number of significant relationships between specific legume species and soil and landscape position. Relationships along landscape positions indicated grass growth concentrated on summit positions and legume growth on sideslope positions would aid in site-specific pasture management techniques. Thereby, site-specific management for particular species across landscape positions can reasonably be expected to reduce the seed, labor and fertilizer costs associated with establishing legumes in topographically variable environments. A greenhouse competition experiment examined competitive ability of smooth bromegrass compared to big bluestem (Andropogon gerardii Vitman, cv. Roundtree) and switchgrass (Panicum virgatum L., cv. Cave-in-Rock) under different temperatures and at increasing planting densities. It was found that smooth bromegrass has a strong ability to compete with warm-season grass species. Smooth bromegrass was less affected by increased plant densities, temperature, and clipping treatments than warm-season grasses. Density of associate species (smooth bromegrass) and temperature affected production of both switchgrass and big bluestem. Smooth bromegrass can provide forage during the cool months, but it is essential to maintain control over populations to allow for warm-season grass production during summer months.



Digital Repository @ Iowa State University,

Copyright Owner

Indi Sue Braden



Proquest ID


File Format


File Size

138 pages