Auftreten und Auswirkungen der Restverunkrautung in Zuckerrueben.
1994
Haberland R.
Surveys have been conducted over a number of years recording the number and fresh weight of residual weeds at the time of canopy and prior to beet harvest in the Magdeburg Boerde and in Bernburg-Loess areas. At the time of canopy a total of 21 different weed species was found, prior to harvesting this number had declined to 16, however, as a rule only between 2 and 4 species were found in one and the same field. Between canopy and harvest there is a natural reduction in the residual weed infestation of about 43 per cent. On the basis of these vegetation samples a marked reduction of weeds for the period of 1990 to 1993 compared with 1975 to 1977 can be seen. There has also been a change in the range of varieties. The dominant varieties currently present include Chenopodium album, Mercurialis annua and Amaranthus retroflexus. The following results concerning the effect of residual weed infestation on sugar beet yields are based on test clearance areas and individual plant variety surveys. Acceptable levels have been established for the most important varieties of weeds occurring in the Boerde. If these weed species are defined in 3 groups according to their development and harmful effects the following acceptable levels of residual weeds per 10 square metre in sugar beets can be established: tall, full species 1 to 1,4; low and/or ground-covering species 3 to 5 and for varieties growing to the same height as the beet plants creating minimum shade 13 to 23.
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