The cultivation of cassava presents several problems in the state of Acre - Brazil, with weed competition being one of the most important and becoming more serious in the Amazon region because weed development is favored by heavy rainfall (around 1900 mm) and high average temperature all over the year. The objective of this research was to determine the total weed interference prevention period in cassava crop and to evaluate the competitiveness of branched and non-branched cassava cultivars. The experiments were carried out at Embrapa Acre Experimental Station in Rio Branco County, state of Acre - Brazil, from 1995 to 1998, comprising seven weeding periods and two cultivars. In one of the experiments, the cultivars studied were Rosada (branched) and Pão (non-branched) and in the next two assays, conducted during the following years, the cultivars grown were IM 319 (branched) and Rasgadinha (non-branched). The parameters evaluated were root and shoot production, contents of cyanide acid and starch as well as rotten root percentage. Cultivar x weeding interaction relative to shoot production was not significant in any year, what shows no competitive advantage of branched over non-branched cultivar. Two weedings provided satisfactory root and shoot yield . The results showed that the total weed interference prevention period in the cassava crop was around 60 days after planting and that the contents of starch, cyanide acid and percentage of rotten root were not influenced by the weeds.
competition; Manihot esculenta; cyanide acid; starch
