ABSTRACT
Summary Studies conducted in Iowa have shown that precision seed placement, good seed-to-soil contact, and reduced competition from other species are just as important when introducing legumes into an existing grass sward as when seeding into a conventional seedbed. Tillage of strips 5.1 cm wide or wider was necessary for adequate sward suppression prior to and during legume establishment. Paraquat (1,1 dimethyl-4,4' bipyridinium ion) at 2.8 or 5.6 kg/ha could substitute for strip tillage in sward suppression. Paraquat banded over the seeded row provided satisfactory sward suppression, but legume establishment was improved when paraquat was applied broadcast or glyphosate [N-(phosphonomethyl) glycine] was band applied. Improved stand densities were obtained when precision placement of seed and press wheels were used, compared with surface seeding with shallow coverage and no soil firming over the seed. Alfalfa (Medicago sativa L.), birdsfoot trefoil (Lotus comiculatw L.), and crownvetch (Coronilla varia L.) have all been successfully established in existing pasture swards via reduced-tillage renovation techniques. Management of sward height postseeding significantly influences the rate of legume establishment in the renovated swards. The greater availability of light for a Bromus-dominated sward managed at a 7.5-cm height resulted in greater density of legume stand, subsequent dry-matter yields, and percentage of legume in the sward than in swards managed at greater heights. In the year following renovation, dry-matter yields of renovated legume swards were similar to those of swards fertilized with 75 kg/ha of N, with a greater proportion of the total yield produced during the summer and early autumn months.
