Competitive capability, selectivity of herbicides and rhizospheric microbial activity of Hymenaea courbaril L seedling.

O presente estudo teve por objetivo avaliar mudas de Hymenea courbaril L. (jatob?) quanto: (a) ? capacidade competitiva com plantas consortes e esp?cies daninhas referentes a aloca??o de mat?ria seca, ?rea foliar e concentra??o de macronutrientes; (b) ? seletividade aos herbicidas sulfentrazone e glyphosate e; (c) aos efeitos de diferentes doses de sulfentrazone sobre a atividade microbiana de substratos cultivados com as mudas. Os experimentos foram conduzidos em casa-de-vegeta??o, viveiro de produ??o de mudas e em laborat?rio na Universidade Federal dos Vales do Jequitinhonha e Mucuri (UFVJM), Diamantina-MG. No ano de 2009, foram conduzidos dois experimentos sendo os tratamentos compostos pela combina??o de mudas de jatob?, se desenvolvendo isoladamente ou em competi??o com cada uma das seguintes esp?cies Brachiaria humidicola, Brachiaria brizantha, Brachiaria decumbens, Panicum maximum, Cajanus cajan, Canavalia ensiformis e Mucuna aterrima (experimento 1) e Cenchrus echinatus L., Bidens pilosa L., Euphorbia heterophylla L., Solanum americanum Mill e Lolium multiflorum Lam. (experimento 2), mais o cultivo isolado de cada planta daninha e consorte, por 60 dias. Al?m do efeito das plantas nas caracter?sticas de altura e mat?ria seca das plantas de jatob?, avaliou-se o ac?mulo de nitrog?nio, f?sforo e pot?ssio em todas as plantas. Em 2010, tamb?m foram conduzidos dois experimentos sendo os tratamentos compostos por dois herbicidas (glyphosate e sulfentrazone) e cinco doses desses herbicidas (0,00; 0,09; 0,18; 0,35 e 0,70 L ha-1) (experimento 1); cinco doses de sulfentrazone (0,00; 0,04; 0,15; 0,30 e 0,60 L ha-1) e dois tipos de substratos (rizosf?rico e n?o rizosf?rico cultivados com mudas de jatob?) (experimento 2), sendo avaliado o potencial de intoxica??o desses produtos sobre a esp?cie vegetal e a comunidade microbiana rizosf?rica. Observou-se que a competi??o entre as plantas n?o promoveu altera??es na produ??o de mat?ria seca ou ?rea foliar do jatob?. Sobre a conviv?ncia das plantas daninhas com o jatob?, constatou-se efeito positivo no ac?mulo de nutrientes por estas. Os herbicidas estudados apresentaram-se com elevado potencial para uso no controle de plantas daninhas em ?reas de plantios de jatob? em fase inicial de desenvolvimento. Quanto aos indicadores microbiol?gicos, verifica-se que a evolu??o do C-CO2 e o carbono da biomassa microbiana foram sens?veis ? presen?a dos herbicidas podendo constituir ferramentas auxiliares no monitoramento do impacto desses produtos no ambiente.Disserta??o (Mestrado) ? Programa de P?s-Gradua??o em Produ??o Vegetal, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2011.ABSTRACT The objective of this study was to evaluate Hymenaea courbaril L (jatoba) seedling in relation to: a) the competitive capability with intercropped plants and weed regarding to dry matter allocation, leaf area and macronutrients concentration. b) The selectivity of herbicides sulfentrazone and glyphosate and, c) the effects of different doses of sulfentrazone on microbial activity of substrates cultivated with the seedling. The experiments were conducted in greenhouse, nursery and laboratory of UFVJM. In 2009, two experiments were carried out, being the treatments a combination of jatoba seedling that had developed alone and/or in competition with one of the following species: Brachiaria humidicola, Brachiaria brizantha, Brachiaria decumbens, Panicum maximum, Cajanus cajan, Canavalia ensiformis and Mucuna aterrima (experiment 1) and Cenchrus echinatus L., Bidens pilosa L., Euphorbia heterophylla L., Solanum americanum Mill and Lolium multiflorum Lam. (experiment 2), plus the isolated cultivation of every weed and plant that was intercropped for 60 days. Besides the effects of the weed plants on height and dry matter of jatoba plants, it was assessed the accumulation of nitrogen, phosphorus and potassium in all of plants. In 2010, it is also made two experiments and the treatment was made with two herbicides (glyphosate and sulfentrazone) and five doses of these herbicides (0,00; 0,09; 0,18; 0,35 e 0,70 L ha-1) (experiment 1); five doses of sulfentrazone (0,00; 0,04; 0,15; 0,30 e 0,60 L ha-1) and two types of substrates (rhizospheric and non-rhizospheric cultivated with jatoba seeding) (experiment 2). It was assessed the poisoning potential of these products on vegetal species and the rhizospheric microbial community. It was observed that the competition between the plants did not trigger changes on production of dry matter or leaf area of jatoba. It was verified a positive effect of nutrients accumulation by weed that lived together with jatoba. These herbicides have showed high potential for use on weed control in areas of jatoba planting in initial phase of development. Regarding to microbiological indicators, it was verified that the C-CO2 and microbial biomass carbon evolution was sensitive to the presence of herbicides that be constitute auxiliary tools on monitoring of the impact of these products