SPYING ESTABLISHMENT OF PERENNIAL RYEGRASS IN WINTER-WHEAT

Catch crops, under-sown in spring cereals and kept growing during autu mn and winter, have been shown to reduce nitrate leaching in several f ield experiments. In Sweden, perennial ryegrass (Lolium perenne L.) is often used as a catch crop, both in experiments and by farmers. Autum n-sown crops such as winter wheat and winter rye are not as efficient as ryegrass in reducing soil nitrogen content during autumn and winter . Thus, to meet the Swedish legislation of keeping arable land covered with catch crops during autumn and winter, it may be necessary to est ablish a catch crop in a growing winter cereal crop. In this study, wi th the objective of evaluate methods for catch crop establishment in w inter cereals, different dates for under-sowing winter wheat with pere nnial ryegrass in spring were compared. Two held experiments per year were carried out during a four-year period. In 1994, double- and singl e-mounted tractor wheels were added as treatments and in 1995-97, two types of seed drills were compared. Under-sowing with ryegrass in spri ng had only minor effects on winter wheat yields. Only very early in w eak wheat stands or very late in wheat already at stem elongation did the action of the seed drill significantly reduce yield. It was observ ed that the choice of drill for under-sowing might influence the wheat yield. In a dense winter wheat crop, fast emergence was important for establishment of a good catch crop. In most cases, the highest number of emerged ryegrass plants was achieved by early under-sowing, since soil water content was generally higher in early spring than in late. On sowing too early, however, soil temperature was too low for accepta ble establishment. Ryegrass establishment and growth were lowest at th e latest sowing dates.