Above-and Below-ground Competition between Chenopodium album and Sugar Beet

The effects of above and below-ground competition between chenopodium album and sugar beet (beta vulgaris) on growth, yield and quality of two sugar beet cultivars of morphologically contrasting growth habit have been investigated afactorial experiment (2 x 4) under glass-house conditions in a randomised complete block design with three replications was done. c. album and two sugar beet cultivars 'amethyst' and 'celt', were subjected to one of four competition regimes as follows: two below-ground competition treatments (± root competition); two above-ground competition treatments (± shoot competition). two seedlings of sugar beet and four of c. album were transplanted at cotyledon stage in plastic pots (44 ern diameter and 35 em deep). plants were harvested 8 (12 leaf stage) and 16 (22 leaf stage) weeks after transplanting (wat). at each harvest, leaf chlorophyll content, plant height, leaf area and shoot and root dry matter of sugar beet and c. album weredetermined. the results demonstrated that there were major differences between growth and yield of the two sugar beet cultivars which were influenced by both above and below-ground competition with c. album. no interactions were observed between beet cultivar and the competition regime, but shoot and root competition inter-acted negatively 8 and 16 wat. both sugar beet shoot and root yield were reduced by shoot and root competition with c. album 8 and 16 wat. however, beet sugar content was unaffected by weed competition regimes. root competition with c. album caused greater reduction of shoot and root yield of sugar beet than shoot competition 16 wat. however, there was no significant difference between shoot and root competition 8 wat. yield loss of sugar beet subject to shoot and root competition with c. album was 47 and 82% respectively. thus, under these conditions, the effect of c .album competition for above-ground resources was less than that for belowgroundresources during a period up to 16 wat.