Competition of Late-Emerging Weeds with Sugarbeets

Weed-free sugarbeets [ Beta vulgaris (L.) Beauv.] growing at a spacing of 60 cm (1/2 stand) yielded the same weight of roots as those spaced 30 cm (full stand), and those spaced 90 cm (1/3 stand) yielded about 90% as much. Gross sucrose yield was reduced somewhat more, because the larger roots growing in partial stands contained a lower percentage of sucrose than the roots in full stands. Annual weeds that emerged after July 1 were suppressed and. killed by competition from sugarbeets of normal vigor in a full stand, but became competitive when the sugarbeets were spaced at 1/2 or 1/3 of a full stand. Competition from barnyardgrass [ Echinochloa crus-galli (L.) Beauv.] and pigweed (mixture of Amaranthus retroflexus L. and A. powellii S. Wats.), which reached a height of 150 cm, reduced root yields 5 to 39% in 1/2 stands and 19 to 49% in 1/3 stands, as compared with weed-free sugarbeets in the same stands. Hairy nightshade ( Solarium sarachoides Sendt.) was abundant but never became taller than the sugarbeets. Its competition had no measurable effect on the sugarbeets.