Effect of Seedbed Preparation Time and Plant Density on the Weed Population of Sugar Beet (Beta vulgaris L.)

For investigation of the effects of seedbed preparation time and plant density of sugar beet on the weed population and quality and quantity characteristics of sugar beet, an experiment was conducted as strip plot design with four replications in the field of Islamic Azad University of Karaj (2007-2008). The first factor included two types of seedbed preparation time (spring and autumn), the second factor included four plant densities of sugar beet (65, 73, 81 and 99 thousand plants per hectare). Seedbed preparation methods were considered as a randomized complete block design and plant density levels as the Latin square design. The result of analysis of variance for the traits related to weeds showed that the effect of seedbed preparation method was significant on number of weed species and weed dry weight. The results of mean comparison showed that the number of weed species and weed dry weight of spring seedbed preparation method was 2-3 times grater than autumn seedbed preparation method. Increasing plant density of sugar beet from 65 to 99 thousand plants per hectare reduced significantly the number and weed dry weight of weed species. The results of yield and quality of sugar beet showed that seedbed preparation in autumn, increased root yield (48.18 t. ha-1) by 21 percent, sugar yield (8.3 t. ha-1) by 26 percent and white sugar yield (6.7 t. ha-1) by 24 percent compared to spring time seedbed preparation. Maximum yield of sugar beet was obtained in plant density of about 100,000 plants per hectare. In conclusion, seedbed preparation in autumn and drilling sugar beet seed in the early spring with 100 thousand plants per hectare may consider as a compilation method to suppress weed populations and increase sugar beet yield