IMPACT OF DRILLING DATE ON APERA-SPICA-VENTI L AND ALOPECURUS-MYOSUROIDES HUDS IN WINTER CEREALS

The impact of drilling date on Apera spica-venti and Alopecurus myosur oides in winter cereals was investigated in field trials in 1991 and 1 992. Two drilling dates were considered with an interval of 14 to 16 d ays between dates. Generally, drilling date had an inconsistent effect on weed plant populations in spring, but seedling emergence of both s pecies appeared to be delayed at the later drilling compared with the earlier date. This delay may partly explain the reduced competitive ab ility of A, myosuroides in wheat in 1991 and 1992 and of A. spica-vent i in wheat in 1991 at the later drilling date. The seed population per plant of both species was lower at the later date in some instances, whereas in others drilling date had no effect. Reduced seed production was mainly caused by a reduction of the number of inflorescences per plant. The potential of utilizing drilling dates as a cultural control measure against grass weeds is discussed.