This research had three components dealing with weed suppression, grazing management, and economics. In the first component, a series of experiments (two field experiments and a greenhouse experiment) were conducted to evaluate weed suppression during the establishment of complex forage mixtures. These series of studies have shown that the use of complex mixtures or FEFS is a viable alternative to annual companion crops for weed suppression during forage establishment. Chicory appeared to be the most effective FEFS in all the studies, hence its use in forage mixtures is recommended during pasture renovation. However caution has to be exercised when adding FEFS to slow establishing forage mixtures because they also will decrease the proportion of the target forage species.

In the second component, a grazing experiment was carried out to evaluate grass in pure stands, simple mixtures, and complex mixtures for their botanical composition, forage nutritive value, and forage production under two grazing management treatments. Among the forages tested, only perennial ryegrass, chicory and red clover were affected by grazing management. Both red clover and chicory produced more under less frequent grazing. On the other hand, perennial ryegrass flourished (increased DM productivity) under more frequent grazing. Legume and weed content decreased as plant diversity increased. Dry matter production was affected by grazing treatment. In general, the "height" grazing treatment produced forage of better nutritive value compared to the "morphology" grazing treatment at first harvest in both years. Fewer differences in nutritive value between grazing treatments were found over the growing season. However when differences were significant, the "height" treatment provided forage of better nutritive value. The effect of forage treatments on nutritive value at first harvest was influenced by both plant diversity and the use of N fertilizer on the orchardgrass. In general, as mixture complexity increased the nutritive value improved. The addition of inorganic N to orchardgrass increased CP content both at first harvest and over the growing season.

In the third component, the short- and long-term economic impact of the forage and grazing treatments were evaluated using results from the previous experiment. The short-term analysis showed that differences between the two grazing managements were mainly due to a smaller pasture production in the "morphology" grazing treatment which led to a decrease in net return of 8% compared to the "height" grazing treatment. Similarly, forage treatment mainly affected pasture production, seed, and fertilizer cost and subsequently the amount of excess forage for sale and the income generated by those sales. Nevertheless, complex mixtures generated greater net returns compared to either the simple mixtures or pure grass stands. Complex forage mixtures presented more consistent net return as a consequence of their consistency in DM production.

The long-term economic analysis showed that the "height" grazing treatment produced greater net return compared to the morphology-based grazing due to greater income from feed and bedding sales and lower feed costs. Additionally, production risk was smaller for the "height" grazing treatment compared to the "morphology" grazing treatment. Comparing the simple mixtures to the complex forage mixtures, differences in feed produced, production costs, and net returns were small. More importantly, when comparing the difference in net return obtained by a particular forage treatment in dry and wet years, the net return using complex mixtures was reduced only by 25 to 27%. On the other hand, net return reductions ranged from 36% for a three species mixture up to 55% for pure grass stands. This gives supporting evidence to the increased consistency both in DM yield and net return of the complex mixtures. (Abstract shortened by UMI.)