Habilidade competitiva de cultivares de sorgo sacarino com plantas daninhas

The aim of this work was to determine the competitive interaction of sweet sorghum cultivars BRS 506, BRS509 and BRS 511 with biotypes of Alexander grass and wild poinsettia. The experimental design adopted was the randomized blocks, with four replications. Treatments was arranged in a substitution series by proportions of 100:0, 75:25, 50:50, 25:75 and 0:100% that corresponded to 20:0, 15:5, 10:10, 5:15 e 0:20 plant per pot of sweet sorghum (cultivars BRS 506, BRS 509 and BRS 511) with weeds (Alexander grass/ wild poinsettia). The leaf area (LA) and dry mass (DM) of sweet sorghum, Alexander grass and wild poinsettia plants were determinate at 50 days after emergence. Data relative to the competitive abilities were analysed through the graphical 4 analysis method, constructing diagrams based on yield or relative and total variations. Also were determinate the indexes of relative competitiveness, clustering coefficient and aggressiveness, all relative indexes. Was observed competition by the same environmental resources between sweet sorghum cultivars with weeds, with mutual injury to the species involved in community. Wild poinsettia and Alexander grass modified negatively the LA and DM of crop demonstrating competitive ability superior by the resources available in the environment. The wild poinsettia was less competitive than sweet sorghum cultivars, while Alexander grass showed higher ability competitive than the same. The highest losses for the variables LA and DM were observed when the species were in competition interspecific than intraspecific.O trabalho teve como objetivo determinar a intera??o competitiva das cultivares de sorgo sacarino BRS 506, BRS 509 e BRS 511 com bi?tipos de papu? e de leiteiro. Os ensaios foram instalados em delineamento completamente casualizado, replicados quatro vezes. Os tratamentos foram dispostos em s?rie substitutiva nas propor??es de; 100:0, 75:25, 50:50, 25:75 e 0:100% o que equivaleu a 20:0, 15:5, 10:10, 5:15 e 0:20 plantas vaso-1 de sorgo sacarino (cultivares BRS 506, BRS 509 e BRS 511) com as plantas daninhas (papu? e/ou leiteiro). A ?rea foliar (AF) e a massa seca (MS) das plantas de sorgo sacarino, do papu? e do leiteiro foram determinadas aos 50 dias ap?s emerg?ncia das esp?cies. Os dados relativos as habilidades competitivas foram analisadas atrav?s do m?todo da an?lise gr?fica, construindo-se diagramas baseados nas produtividades ou varia??es relativas e totais. Determinou-se tamb?m os ?ndices de competitividade, coeficiente de agrupamento e agressividade, todos esses ?ndices relativos. Ocorreu competi??o pelos mesmos recursos do meio entre as cultivares de sorgo sacarino com as plantas daninhas, com preju?zo m?tuo ?s esp?cies envolvidas na comunidade. O leiteiro e o papu? modificaram de forma negativa a AF e a MS da cultura demonstrando habilidade competitiva superior pelos recursos dispon?veis no meio. O leiteiro foi menos competitivo que ?s cultivares de sorgo sacarino, enquanto que o papu? apresentou maior competitividade do que as mesmas. Os maiores preju?zos para as vari?veis AF e MS foram observados quando as esp?cies estiveram em competi??o interespec?fica do que em competi??o intraespec?fica