Weed competition in sugar beets and its practical utilisation

The major aim of these field experiments carried out at Lautenbach (Dis. Heilbronn) between 1979 and 1982 is to evaluate competitive effects of weed on the yield components of sugar beet. In these studies, only the period up to 50 days after 50 per cent emergence is considered. The number of established beet plants increased, when weed removal is delayed up to 50 days. During this time, no correlation was observed between duration of weed competition and the plant density. In contrast, the weight of beets was affected by the duration of weed competition. Allowing weeds to grow for more than 30 days after emergence of the beets caused a reduction of the final yields. On the other hand, when weed remain in densities up to 200 plants/square meter for less than 30 days, no losses were observed. Neither leaf weight nor sugar contents were affected by weed competition. It is concluded that it is safe to allow weeds to grow in sugar beet crops up to 30 days after emergence. In integrated management systems, "presowing weed control" is to be excluded