Abstract
Effects of paraquat application, and seed-bed preparation by surface cultivation were investigated in order to sod-seed red clover (Trifolium pratense L.) into timothy (Phleum pratense L.) -dominant swards. The following results were obtained : 1) Suppression of timothy by paraquat application was related to its dose, amount of timothy canopy at the application time and duration from harvest to spraying. Moreover, it was suggested that the effect of paraquat application on timothy varied greatly with weather condition ; under drought and high temperature, timothy almost died by spraying 19 to 95 g/10 a (active ingredient) of paraquat and was suppressed even by 9 g/10 a. Consequently, it was considered that using paraquat as a method of temporary suppression of timothy at sod-seeding was very risky for practical use. 2) The partial treatment of sward surface using slot seeder (John Deere Powr-till Seeder) or the overall treatment of sward surface by disk harrow, if it was followed by compaction, offered good seed-bed for sod-seeding red clover. However, the emergence and establishment of sod-seeded red clover was poor in non-treatment sward, especially under the drought condition.
